Append a record to the end of a text file
You are encouraged to solve this task according to the task description, using any language you may know.
Many systems offer the ability to open a file for writing, such that any data written will be appended to the end of the file. Further, the file operations will always adjust the position pointer to guarantee the end of the file, even in a multitasking environment.
This feature is most useful in the case of log files, where many jobs may be appending to the log file at the same time, or where care must be taken to avoid concurrently overwriting the same record from another job.
- Task
Given a two record sample for a mythical "passwd" file:
- Write these records out in the typical system format.
- Ideally these records will have named fields of various types.
- Close the file, then reopen the file for append.
- Append a new record to the file and close the file again.
- Take appropriate care to avoid concurrently overwrites from another job.
- Open the file and demonstrate the new record has indeed written to the end.
| account | password | UID | GID | fullname,office,extension,homephone,email | directory | shell |
|---|---|---|---|---|---|---|
| string | string | int | int | struct(string,string,string,string,string) | string | string |
| jsmith | x | 1001 | 1000 | Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org | /home/jsmith | /bin/bash |
| jdoe | x | 1002 | 1000 | Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org | /home/jdoe | /bin/bash |
| account | password | UID | GID | fullname,office,extension,homephone,email | directory | shell |
|---|---|---|---|---|---|---|
| string | string | int | int | struct(string,string,string,string,string) | string | string |
| xyz | x | 1003 | 1000 | X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org | /home/xyz | /bin/bash |
Resulting file format: should mimic Linux's /etc/passwd file format with particular attention to the "," separator used in the GECOS field. But if the specific language has a particular or unique format of storing records in text file, then this format should be named and demonstrated with an additional example.
Expected output:
Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Finally: Provide a summary of the language's "append record" capabilities in a table. eg.
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| C struct | CSV text file | glibc/stdio | ☑ | ☑ | ☑ (Not all, eg NFS) |
Alternatively: If the language's appends can not guarantee its writes will always append, then note this restriction in the table. If possible, provide an actual code example (possibly using file/record locking) to guarantee correct concurrent appends.
Action!
PROC CreateLog(CHAR ARRAY fname)
CHAR ARRAY header="account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell"
BYTE dev=[1]
Close(dev)
Open(dev,fname,8)
PrintDE(dev,header)
Close(dev)
RETURN
PROC AppendLog(CHAR ARRAY fname,line)
BYTE dev=[1]
Close(dev)
Open(dev,fname,9)
PrintDE(dev,line)
Close(dev)
RETURN
PROC ReadFile(CHAR ARRAY fname)
CHAR ARRAY line(255)
BYTE dev=[1]
Close(dev)
Open(dev,fname,4)
WHILE Eof(dev)=0
DO
InputSD(dev,line)
IF line(0) THEN
PutE() Print(line)
FI
OD
Close(dev)
RETURN
PROC PrintInv(CHAR ARRAY a)
BYTE i
IF a(0)>0 THEN
FOR i=1 TO a(0)
DO
Put(a(i)%$80)
OD
FI
RETURN
PROC Main()
CHAR ARRAY fname="D:PASSWD"
BYTE LMARGIN=$52,oldLMARGIN
oldLMARGIN=LMARGIN
LMARGIN=0 ;remove left margin on the screen
Put(125) PutE() ;clear the screen
CreateLog(fname)
AppendLog(fname,"jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash")
AppendLog(fname,"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash")
PrintInv("Initial log:")
ReadFile(fname)
AppendLog(fname,"xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash")
PutE() PrintInv("Updated log:")
ReadFile(fname)
LMARGIN=oldLMARGIN ;restore left margin on the screen
RETURN- Output:
Screenshot from Atari 8-bit computer
Initial log: account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash Updated log: account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Ada
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
with Ada.Strings.Bounded;
procedure Main is
package data_string is new Ada.Strings.Bounded.Generic_Bounded_Length(80);
use data_string;
type GCOSE_Rec is record
Full_Name : Bounded_String;
Office : Bounded_String;
Extension : Bounded_String;
Homephone : Bounded_String;
Email : Bounded_String;
end record;
type Password_Rec is record
Account : Bounded_String;
Password : Bounded_String;
Uid : Natural;
Gid : Natural;
GCOSE : GCOSE_Rec;
Directory : Bounded_String;
Shell : Bounded_String;
end record;
function To_String(Item : GCOSE_Rec) return String is
begin
return To_String(Item.Full_Name) & "," &
To_String(Item.Office) & "," &
To_String(Item.Extension) & "," &
To_String(Item.Homephone) & "," &
To_String(Item.Email);
end To_String;
function To_String(Item : Password_Rec) return String is
uid_str : string(1..4);
gid_str : string(1..4);
Temp : String(1..5);
begin
Temp := Item.Uid'Image;
uid_str := Temp(2..5);
Temp := Item.Gid'Image;
gid_str := Temp(2..5);
return To_String(Item.Account) & ":" &
To_String(Item.Password) & ":" &
uid_str & ":" & gid_str & ":" &
To_String(Item.GCOSE) & ":" &
To_String(Item.Directory) & ":" &
To_String(Item.Shell);
end To_String;
Pwd_List : array (1..3) of Password_Rec;
Filename : String := "password.txt";
The_File : File_Type;
Line : String(1..256);
Length : Natural;
begin
Pwd_List(1) := (Account => To_Bounded_String("jsmith"),
Password => To_Bounded_String("x"),
Uid => 1001, GID => 1000,
GCOSE => (Full_Name => To_Bounded_String("Joe Smith"),
Office => To_Bounded_String("Room 1007"),
Extension => To_Bounded_String("(234)555-8917"),
Homephone => To_Bounded_String("(234)555-0077"),
email => To_Bounded_String("jsmith@rosettacode.org")),
directory => To_Bounded_String("/home/jsmith"),
shell => To_Bounded_String("/bin/bash"));
Pwd_List(2) := (Account => To_Bounded_String("jdoe"),
Password => To_Bounded_String("x"),
Uid => 1002, GID => 1000,
GCOSE => (Full_Name => To_Bounded_String("Jane Doe"),
Office => To_Bounded_String("Room 1004"),
Extension => To_Bounded_String("(234)555-8914"),
Homephone => To_Bounded_String("(234)555-0044"),
email => To_Bounded_String("jdoe@rosettacode.org")),
directory => To_Bounded_String("/home/jdoe"),
shell => To_Bounded_String("/bin/bash"));
Pwd_List(3) := (Account => To_Bounded_String("xyz"),
Password => To_Bounded_String("x"),
Uid => 1003, GID => 1000,
GCOSE => (Full_Name => To_Bounded_String("X Yz"),
Office => To_Bounded_String("Room 1003"),
Extension => To_Bounded_String("(234)555-8913"),
Homephone => To_Bounded_String("(234)555-0033"),
email => To_Bounded_String("xyz@rosettacode.org")),
directory => To_Bounded_String("/home/xyz"),
shell => To_Bounded_String("/bin/bash"));
Create(File => The_File,
Mode => Out_File,
Name => Filename);
for I in 1..2 loop
Put_Line(File => The_File,
Item => To_String(Pwd_List(I)));
end loop;
Reset(File => The_File,
Mode => In_File);
while not End_Of_File(The_File) loop
Get_Line(File => The_File,
Item => Line,
Last => Length);
Put_Line(Line(1..Length));
end loop;
New_Line;
Reset(File => The_File,
Mode => Append_File);
Put_Line(File => The_File,
Item => To_String(Pwd_List(3)));
Reset(File => The_File,
Mode => In_File);
while not End_Of_File(The_File) loop
Get_Line(File => The_File,
Item => Line,
Last => Length);
Put_Line(Line(1..Length));
end loop;
Close(The_File);
end Main;
- Output:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
AWK
# syntax: GAWK -f APPEND_A_RECORD_TO_THE_END_OF_A_TEXT_FILE.AWK
BEGIN {
fn = "\\etc\\passwd"
# create and populate file
print("account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell") >fn
print("jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash") >fn
print("jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash") >fn
close(fn)
show_file("initial file")
# append record
print("xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash") >>fn
close(fn)
show_file("file after append")
exit(0)
}
function show_file(desc, nr,rec) {
printf("%s:\n",desc)
while (getline rec <fn > 0) {
nr++
printf("%s\n",rec)
}
close(fn)
printf("%d records\n\n",nr)
}
Output:
initial file: account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash 3 records file after append: account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash 4 records
Batch File
@echo off
(
echo jsmith:x:1001:1000:Joe Smith,Room 1007,^(234^)555-8917,^(234^)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash
echo jdoe:x:1002:1000:Jane Doe,Room 1004,^(234^)555-8914,^(234^)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash
) > append.txt
echo Current contents of append.txt:
type append.txt
echo.
echo xyz:x:1003:1000:X Yz,Room 1003,^(234^)555-8913,^(234^)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash >> append.txt
echo New contents of append.txt:
type append.txt
pause>nul
- Output:
Current contents of append.txt: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash New contents of append.txt: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
C
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| C struct | CSV text file | glibc/stdio | ☑ | ☑ | ☑ (Not all, eg NFS) |
Note: Not all File Systems support atomic appends. In particular NFS does not. It is not known if there is a standard OS independent way of detecting if atomic appends are available. However most Unix & Linux File Systems do support atomic appends, especially for log files.
From a C "struct" to CSV File
#include <stdio.h>
#include <string.h>
/* note that UID & GID are of type "int" */
typedef const char *STRING;
typedef struct{STRING fullname, office, extension, homephone, email; } gecos_t;
typedef struct{STRING account, password; int uid, gid; gecos_t gecos; STRING directory, shell; } passwd_t;
#define GECOS_FMT "%s,%s,%s,%s,%s"
#define PASSWD_FMT "%s:%s:%d:%d:"GECOS_FMT":%s:%s"
passwd_t passwd_list[]={
{"jsmith", "x", 1001, 1000, /* UID and GID are type int */
{"Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org"},
"/home/jsmith", "/bin/bash"},
{"jdoe", "x", 1002, 1000,
{"Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org"},
"/home/jdoe", "/bin/bash"}
};
main(){
/****************************
* Create a passwd text file *
****************************/
FILE *passwd_text=fopen("passwd.txt", "w");
int rec_num;
for(rec_num=0; rec_num < sizeof passwd_list/sizeof(passwd_t); rec_num++)
fprintf(passwd_text, PASSWD_FMT"\n", passwd_list[rec_num]);
fclose(passwd_text);
/********************************
* Load text ready for appending *
********************************/
passwd_text=fopen("passwd.txt", "a+");
char passwd_buf[BUFSIZ]; /* warning: fixed length */
passwd_t new_rec =
{"xyz", "x", 1003, 1000, /* UID and GID are type int */
{"X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org"},
"/home/xyz", "/bin/bash"};
sprintf(passwd_buf, PASSWD_FMT"\n", new_rec);
/* An atomic append without a file lock,
Note: wont work on some file systems, eg NFS */
write(fileno(passwd_text), passwd_buf, strlen(passwd_buf));
close(passwd_text);
/***********************************************
* Finally reopen and check record was appended *
***********************************************/
passwd_text=fopen("passwd.txt", "r");
while(!feof(passwd_text))
fscanf(passwd_text, "%[^\n]\n", passwd_buf, "\n");
if(strstr(passwd_buf, "xyz"))
printf("Appended record: %s\n", passwd_buf);
}
- Output:
Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
C#
using System;
using System.IO;
namespace AppendPwdRosetta
{
class PasswordRecord
{
public string account, password, fullname, office, extension, homephone, email, directory, shell;
public int UID, GID;
public PasswordRecord(string account, string password, int UID, int GID, string fullname, string office, string extension, string homephone,
string email, string directory, string shell)
{
this.account = account; this.password = password; this.UID = UID; this.GID = GID; this.fullname = fullname; this.office = office;
this.extension = extension; this.homephone = homephone; this.email = email; this.directory = directory; this.shell = shell;
}
public override string ToString()
{
var gecos = string.Join(",", new string[] { fullname, office, extension, homephone, email });
return string.Join(":", new string[] { account, password, UID.ToString(), GID.ToString(), gecos, directory, shell });
}
}
class Program
{
static void Main(string[] args)
{
var jsmith = new PasswordRecord("jsmith", "x", 1001, 1000, "Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org",
"/home/jsmith", "/bin/bash");
var jdoe = new PasswordRecord("jdoe", "x", 1002, 1000, "Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org", "/home/jdoe",
"/bin/bash");
var xyz = new PasswordRecord("xyz", "x", 1003, 1000, "X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org", "/home/xyz", "/bin/bash");
// Write these records out in the typical system format.
File.WriteAllLines("passwd.txt", new string[] { jsmith.ToString(), jdoe.ToString() });
// Append a new record to the file and close the file again.
File.AppendAllText("passwd.txt", xyz.ToString());
// Open the file and demonstrate the new record has indeed written to the end.
string[] lines = File.ReadAllLines("passwd.txt");
Console.WriteLine("Appended record: " + lines[2]);
}
}
}
- Output:
>AppendPwdRosetta.exe Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
C++
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
std::ostream& operator<<(std::ostream& out, const std::string s) {
return out << s.c_str();
}
struct gecos_t {
std::string fullname, office, extension, homephone, email;
friend std::ostream& operator<<(std::ostream&, const gecos_t&);
};
std::ostream& operator<<(std::ostream& out, const gecos_t& g) {
return out << g.fullname << ',' << g.office << ',' << g.extension << ',' << g.homephone << ',' << g.email;
}
struct passwd_t {
std::string account, password;
int uid, gid;
gecos_t gecos;
std::string directory, shell;
passwd_t(const std::string& a, const std::string& p, int u, int g, const gecos_t& ge, const std::string& d, const std::string& s)
: account(a), password(p), uid(u), gid(g), gecos(ge), directory(d), shell(s)
{
//empty
}
friend std::ostream& operator<<(std::ostream&, const passwd_t&);
};
std::ostream& operator<<(std::ostream& out, const passwd_t& p) {
return out << p.account << ':' << p.password << ':' << p.uid << ':' << p.gid << ':' << p.gecos << ':' << p.directory << ':' << p.shell;
}
std::vector<passwd_t> passwd_list{
{
"jsmith", "x", 1001, 1000,
{"Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org"},
"/home/jsmith", "/bin/bash"
},
{
"jdoe", "x", 1002, 1000,
{"Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org"},
"/home/jdoe", "/bin/bash"
}
};
int main() {
// Write the first two records
std::ofstream out_fd("passwd.txt");
for (size_t i = 0; i < passwd_list.size(); ++i) {
out_fd << passwd_list[i] << '\n';
}
out_fd.close();
// Append the third record
out_fd.open("passwd.txt", std::ios::app);
out_fd << passwd_t("xyz", "x", 1003, 1000, { "X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org" }, "/home/xyz", "/bin/bash") << '\n';
out_fd.close();
// Verify the record was appended
std::ifstream in_fd("passwd.txt");
std::string line, temp;
while (std::getline(in_fd, temp)) {
// the last line of the file is empty, make sure line contains the last record
if (!temp.empty()) {
line = temp;
}
}
if (line.substr(0, 4) == "xyz:") {
std::cout << "Appended record: " << line << '\n';
} else {
std::cout << "Failed to find the expected record appended.\n";
}
return 0;
}
- Output:
Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
COBOL
COBOL is a record oriented language. Commonly referred to as ISAM, Indexed Sequential Access Mode IO, is the main type of file operations with COBOL, but that is never quite technically correct as there can be various file handling subsystems included with a COBOL installation.
GnuCOBOL supports ISAM for SEQUENTIAL, RANDOM and INDEXED file organizations, that can be accessed with SEQUENTIAL, RANDOM and DYNAMIC modes.
LINE SEQUENTIAL access (an extension to standard COBOL) is also supported for "normal" newline delimited text files. The GnuCOBOL compiler source kit ships with a choice of four different file subsystem configurations, as well as allowing external site defined handlers during compiler builds. So, even though it is a common expression, ISAM is rarely a complete or technically correct statement. IBM COBOL dialects support a wide variety of mainframe file access subsystems, for instance.
With GnuCOBOL, normal text file operations rely on the POSIX layer, and have features very similar (or identical) to the technical interface enjoyed by C.
OPEN EXTEND provides automatic file appends. OPEN I-O allows for program controlled appends with START LAST, READ NEXT and READ PREVIOUS positioning control, paired with WRITE and REWRITE statements.
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Record hierarchy | text file | POSIX | ☑ | ☑ | ☑ (Not all, eg TAPE devices) |
| Record hierarchy | SEQUENTIAL | POSIX/ISAM | ☑ | ☑ | ☑ (Not all) |
| Record hierarchy | RANDOM | POSIX/ISAM | ☑ | ☑ | ☑ (Not all) |
| Record hierarchy | INDEXED | ISAM | ☑ | ☑ | ☑ (Not all) |
Note: Not all File Systems support atomic appends. In particular NFS, and many TAPE devices do not. Guaranteed atomic append operations will be highly dependent on file handling subsystem and device capabilities.
Record group to passwd format, LINE SEQUENTIAL
*> Tectonics:
*> cobc -xj append.cob
*> cobc -xjd -DDEBUG append.cob
*> ***************************************************************
identification division.
program-id. append.
environment division.
configuration section.
repository.
function all intrinsic.
input-output section.
file-control.
select pass-file
assign to pass-filename
organization is line sequential
status is pass-status.
REPLACE ==:LRECL:== BY ==2048==.
data division.
file section.
fd pass-file record varying depending on pass-length.
01 fd-pass-record.
05 filler pic x occurs 0 to :LRECL: times
depending on pass-length.
working-storage section.
01 pass-filename.
05 filler value "passfile".
01 pass-status pic xx.
88 ok-status values '00' thru '09'.
88 eof-pass value '10'.
01 pass-length usage index.
01 total-length usage index.
77 file-action pic x(11).
01 pass-record.
05 account pic x(64).
88 key-account value "xyz".
05 password pic x(64).
05 uid pic z(4)9.
05 gid pic z(4)9.
05 details.
10 fullname pic x(128).
10 office pic x(128).
10 extension pic x(32).
10 homephone pic x(32).
10 email pic x(256).
05 homedir pic x(256).
05 shell pic x(256).
77 colon pic x value ":".
77 comma-mark pic x value ",".
77 newline pic x value x"0a".
*> ***************************************************************
procedure division.
main-routine.
perform initial-fill
>>IF DEBUG IS DEFINED
display "Initial data:"
perform show-records
>>END-IF
perform append-record
>>IF DEBUG IS DEFINED
display newline "After append:"
perform show-records
>>END-IF
perform verify-append
goback
.
*> ***************************************************************
initial-fill.
perform open-output-pass-file
move "jsmith" to account
move "x" to password
move 1001 to uid
move 1000 to gid
move "Joe Smith" to fullname
move "Room 1007" to office
move "(234)555-8917" to extension
move "(234)555-0077" to homephone
move "jsmith@rosettacode.org" to email
move "/home/jsmith" to homedir
move "/bin/bash" to shell
perform write-pass-record
move "jdoe" to account
move "x" to password
move 1002 to uid
move 1000 to gid
move "Jane Doe" to fullname
move "Room 1004" to office
move "(234)555-8914" to extension
move "(234)555-0044" to homephone
move "jdoe@rosettacode.org" to email
move "/home/jdoe" to homedir
move "/bin/bash" to shell
perform write-pass-record
perform close-pass-file
.
*> **********************
check-pass-file.
if not ok-status then
perform file-error
end-if
.
*> **********************
check-pass-with-eof.
if not ok-status and not eof-pass then
perform file-error
end-if
.
*> **********************
file-error.
display "error " file-action space pass-filename
space pass-status upon syserr
move 1 to return-code
goback
.
*> **********************
append-record.
move "xyz" to account
move "x" to password
move 1003 to uid
move 1000 to gid
move "X Yz" to fullname
move "Room 1003" to office
move "(234)555-8913" to extension
move "(234)555-0033" to homephone
move "xyz@rosettacode.org" to email
move "/home/xyz" to homedir
move "/bin/bash" to shell
perform open-extend-pass-file
perform write-pass-record
perform close-pass-file
.
*> **********************
open-output-pass-file.
open output pass-file with lock
move "open output" to file-action
perform check-pass-file
.
*> **********************
open-extend-pass-file.
open extend pass-file with lock
move "open extend" to file-action
perform check-pass-file
.
*> **********************
open-input-pass-file.
open input pass-file
move "open input" to file-action
perform check-pass-file
.
*> **********************
close-pass-file.
close pass-file
move "closing" to file-action
perform check-pass-file
.
*> **********************
write-pass-record.
set total-length to 1
set pass-length to :LRECL:
string
account delimited by space
colon
password delimited by space
colon
trim(uid leading) delimited by size
colon
trim(gid leading) delimited by size
colon
trim(fullname trailing) delimited by size
comma-mark
trim(office trailing) delimited by size
comma-mark
trim(extension trailing) delimited by size
comma-mark
trim(homephone trailing) delimited by size
comma-mark
email delimited by space
colon
trim(homedir trailing) delimited by size
colon
trim(shell trailing) delimited by size
into fd-pass-record with pointer total-length
on overflow
display "error: fd-pass-record truncated at "
total-length upon syserr
end-string
set pass-length to total-length
set pass-length down by 1
write fd-pass-record
move "writing" to file-action
perform check-pass-file
.
*> **********************
read-pass-file.
read pass-file
move "reading" to file-action
perform check-pass-with-eof
.
*> **********************
show-records.
perform open-input-pass-file
perform read-pass-file
perform until eof-pass
perform show-pass-record
perform read-pass-file
end-perform
perform close-pass-file
.
*> **********************
show-pass-record.
display fd-pass-record
.
*> **********************
verify-append.
perform open-input-pass-file
move 0 to tally
perform read-pass-file
perform until eof-pass
add 1 to tally
unstring fd-pass-record delimited by colon
into account
if key-account then exit perform end-if
perform read-pass-file
end-perform
if (key-account and tally not > 2) or (not key-account) then
display
"error: appended record not found in correct position"
upon syserr
else
display "Appended record: " with no advancing
perform show-pass-record
end-if
perform close-pass-file
.
end program append.
- Output:
prompt$ cobc -xj append.cob Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Common Lisp
Tested on CLISP 2.49
(defvar *initial_data*
(list
(list "jsmith" "x" 1001 1000
(list "Joe Smith" "Room 1007" "(234)555-8917" "(234)555-0077" "jsmith@rosettacode.org")
"/home/jsmith" "/bin/bash")
(list "jdoe" "x" 1002 1000
(list "Jane Doe" "Room 1004" "(234)555-8914" "(234)555-0044" "jdoe@rosettacode.org")
"/home/jdoe" "/bin/bash")))
(defvar *insert*
(list "xyz" "x" 1003 1000
(list "X Yz" "Room 1003" "(234)555-8913" "(234)555-0033" "xyz@rosettacode.org")
"/home/xyz" "/bin/bash"))
(defun serialize (record delim)
(string-right-trim delim ;; Remove trailing delimiter
(reduce (lambda (a b)
(typecase b
(list (concatenate 'string a (serialize b ",") delim))
(t (concatenate 'string a
(typecase b
(integer (write-to-string b))
(t b))
delim))))
record :initial-value "")))
(defun main ()
;; Write initial values to file
(with-open-file (stream "./passwd"
:direction :output
:if-exists :supersede
:if-does-not-exist :create)
(loop for x in *initial_data* do
(format stream (concatenate 'string (serialize x ":") "~%"))))
;; Reopen file, append insert value
(with-open-file (stream "./passwd"
:direction :output
:if-exists :append)
(format stream (concatenate 'string (serialize *insert* ":") "~%")))
;; Reopen file, search for new record
(with-open-file (stream "./passwd")
(when stream
(loop for line = (read-line stream nil)
while line do
(if (search "xyz" line)
(format t "Appended record: ~a~%" line))))))
(main)
- Output:
$ clisp append_file.cl Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Lists | Text file | Common Lisp Standard Library | ☑ | ☑ | ☑ (Hopefully!) |
D
class Record {
private const string account;
private const string password;
private const int uid;
private const int gid;
private const string[] gecos;
private const string directory;
private const string shell;
public this(string account, string password, int uid, int gid, string[] gecos, string directory, string shell) {
import std.exception;
this.account = enforce(account);
this.password = enforce(password);
this.uid = uid;
this.gid = gid;
this.gecos = enforce(gecos);
this.directory = enforce(directory);
this.shell = enforce(shell);
}
public void toString(scope void delegate(const(char)[]) sink) const {
import std.conv : toTextRange;
import std.format : formattedWrite;
import std.range : put;
sink(account);
put(sink, ':');
sink(password);
put(sink, ':');
toTextRange(uid, sink);
put(sink, ':');
toTextRange(gid, sink);
put(sink, ':');
formattedWrite(sink, "%-(%s,%)", gecos);
put(sink, ':');
sink(directory);
put(sink, ':');
sink(shell);
}
}
public Record parse(string text) {
import std.array : split;
import std.conv : to;
import std.string : chomp;
string[] tokens = text.chomp.split(':');
return new Record(
tokens[0],
tokens[1],
to!int(tokens[2]),
to!int(tokens[3]),
tokens[4].split(','),
tokens[5],
tokens[6]);
}
void main() {
import std.algorithm : map;
import std.file : exists, mkdir;
import std.stdio;
auto rawData = [
"jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash",
"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash",
"xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash"
];
auto records = rawData.map!parse;
if (!exists("_rosetta")) {
mkdir("_rosetta");
}
auto passwd = File("_rosetta/.passwd", "w");
passwd.lock();
passwd.writeln(records[0]);
passwd.writeln(records[1]);
passwd.unlock();
passwd.close();
passwd.open("_rosetta/.passwd", "a");
passwd.lock();
passwd.writeln(records[2]);
passwd.unlock();
passwd.close();
passwd.open("_rosetta/.passwd");
foreach(string line; passwd.lines()) {
parse(line).writeln();
}
passwd.close();
}
- Output:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
ed
H
r append.input
,p
a
xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
.
w
,p
q
- Output:
$ ed -s < append.ed Newline appended account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| text lines | /etc/passwd format file | editor functionality | ☑ | ☑ | ☑ |
Elixir
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| objects (subclass of Struct builtin) | text file | builtin | ☑ | ☑ | ☒ |
defmodule Gecos do
defstruct [:fullname, :office, :extension, :homephone, :email]
defimpl String.Chars do
def to_string(gecos) do
[:fullname, :office, :extension, :homephone, :email]
|> Enum.map_join(",", &Map.get(gecos, &1))
end
end
end
defmodule Passwd do
defstruct [:account, :password, :uid, :gid, :gecos, :directory, :shell]
defimpl String.Chars do
def to_string(passwd) do
[:account, :password, :uid, :gid, :gecos, :directory, :shell]
|> Enum.map_join(":", &Map.get(passwd, &1))
end
end
end
defmodule Appender do
def write(filename) do
jsmith = %Passwd{
account: "jsmith",
password: "x",
uid: 1001,
gid: 1000,
gecos: %Gecos{
fullname: "Joe Smith",
office: "Room 1007",
extension: "(234)555-8917",
homephone: "(234)555-0077",
email: "jsmith@rosettacode.org"
},
directory: "/home/jsmith",
shell: "/bin/bash"
}
jdoe = %Passwd{
account: "jdoe",
password: "x",
uid: 1002,
gid: 1000,
gecos: %Gecos{
fullname: "Jane Doe",
office: "Room 1004",
extension: "(234)555-8914",
homephone: "(234)555-0044",
email: "jdoe@rosettacode.org"
},
directory: "/home/jdoe",
shell: "/bin/bash"
}
xyz = %Passwd{
account: "xyz",
password: "x",
uid: 1003,
gid: 1000,
gecos: %Gecos{
fullname: "X Yz",
office: "Room 1003",
extension: "(234)555-8913",
homephone: "(234)555-0033",
email: "xyz@rosettacode.org"
},
directory: "/home/xyz",
shell: "/bin/bash"
}
File.open!(filename, [:write], fn file ->
IO.puts(file, jsmith)
IO.puts(file, jdoe)
end)
File.open!(filename, [:append], fn file ->
IO.puts(file, xyz)
end)
IO.puts File.read!(filename)
end
end
Appender.write("passwd.txt")
- Output:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Fortran
Prior to F90, data aggregates can't be defined so one would use an assemblage of variables (perhaps with similar names) and be diligent over every READ and WRITE statement naming them all and in the right order. With F90 the assemblage can be declared via a single name such as NOTE which has subcomponents, if defined via repeated use of TYPE. In COBOL and pl/i, the definition of an aggregate can be done more smoothly. A further difficulty is that character variables have a fixed size, and there is no length field to allow a "string" style usage. Fortran 2003 formalised a scheme whereby character variables can be re-allocated with a suitable size on assignment so that for example NOTE.ACCOUNT = "Fred" would regenerate the variable as a four-character text until it was next assigned to, and there would be no trailing spaces as there are when the variable's length is fixed at 28. However, when written, there is no indication of the actual length of such a variable.
In the absence of a length indication, when outputting text variables with a view to having them read in again, delimiting them with quotes (and doubling internal quotes) is the route to peace of mind, because otherwise a text might contain a comma as in "43 Gurney Road, Belmont" and in the absence of quoting, such a sequence on input might well be taken as two fields rather than one and a mess is certain. This facility is offered by the free-format (or, "list directed") style initiated by the use of * in place of a format label, as in WRITE (MSG,*) etc., provided however that the output file has been opened with the optional usage attribute DELIM = "QUOTE", an unfortunate choice of name, because the field separator character could also be termed a "delimiter" and the default value is both a space or comma, when often what is preferable is only a comma, or even a tab. But there is no standard method to specify this desire. Only if the texts never themselves contain commas or spaces will this unquoted free-format scheme evade extra effort, and the specified example precludes this simplicity.
The resulting output is strung along an output line, with a default line length of 132 (a standard lineprinter width); the specification of RECL = 666 ensures that all the output fields are rolled to one line - that isn't padded out to 666 characters: this is not a fixed-length record despite the specification of RECL as a constant, though each record turns out to be 248 characters long. Unfortunately, the trailing spaces in each character variable are rolled forth and there is no option along the lines of WRITE (MSG,*) TRIM(NOTE) One could instead use a suitable FORMAT statement with "A" format codes, but every element of NOTE would have to be named in the output list and the TRIM function applied only to each character field. Not only would this be tedious and error-prone, there is no format code for the enquoting and double-quoting of the texts and thus, no peace of mind... One would of course devise a subroutine to write out such a record (which would probably be more complex, with the FULLNAME subdivided, etc.), but the task's main objective is to demonstrate appending output to a file.
PROGRAM DEMO !As per the described task, more or less.
TYPE DETAILS !Define a component.
CHARACTER*28 FULLNAME
CHARACTER*12 OFFICE
CHARACTER*16 EXTENSION
CHARACTER*16 HOMEPHONE
CHARACTER*88 EMAIL
END TYPE DETAILS
TYPE USERSTUFF !Define the desired data aggregate.
CHARACTER*8 ACCOUNT
CHARACTER*8 PASSWORD !Plain text!! Eeek!!!
INTEGER*2 UID
INTEGER*2 GID
TYPE(DETAILS) PERSON
CHARACTER*18 DIRECTORY
CHARACTER*12 SHELL
END TYPE USERSTUFF
TYPE(USERSTUFF) NOTE !After all that, I'll have one.
NAMELIST /STUFF/ NOTE !Enables free-format I/O, with names.
INTEGER F,MSG,N
MSG = 6 !Standard output.
F = 10 !Suitable for some arbitrary file.
OPEN(MSG, DELIM = "QUOTE") !Text variables are to be enquoted.
Create the file and supply its initial content.
OPEN (F, FILE="Staff.txt",STATUS="REPLACE",ACTION="WRITE",
1 DELIM="QUOTE",RECL=666) !Special parameters for the free-format WRITE working.
WRITE (F,*) USERSTUFF("jsmith","x",1001,1000,
1 DETAILS("Joe Smith","Room 1007","(234)555-8917",
2 "(234)555-0077","jsmith@rosettacode.org"),
2 "/home/jsmith","/bin/bash")
WRITE (F,*) USERSTUFF("jdoe","x",1002,1000,
1 DETAILS("Jane Doe","Room 1004","(234)555-8914",
2 "(234)555-0044","jdoe@rosettacode.org"),
3 "home/jdoe","/bin/bash")
CLOSE (F) !The file is now existing.
Choose the existing file, and append a further record to it.
OPEN (F, FILE="Staff.txt",STATUS="OLD",ACTION="WRITE",
1 DELIM="QUOTE",RECL=666,ACCESS="APPEND")
NOTE = USERSTUFF("xyz","x",1003,1000, !Create a new record's worth of stuff.
1 DETAILS("X Yz","Room 1003","(234)555-8193",
2 "(234)555-033","xyz@rosettacode.org"),
3 "/home/xyz","/bin/bash")
WRITE (F,*) NOTE !Append its content to the file.
CLOSE (F)
Chase through the file, revealing what had been written..
OPEN (F, FILE="Staff.txt",STATUS="OLD",ACTION="READ",
1 DELIM="QUOTE",RECL=666)
N = 0
10 READ (F,*,END = 20) NOTE !As it went out, so it comes in.
N = N + 1 !Another record read.
WRITE (MSG,11) N !Announce.
11 FORMAT (/,"Record ",I0) !Thus without quotes around the text part.
WRITE (MSG,STUFF) !Reveal.
GO TO 10 !Try again.
Closedown.
20 CLOSE (F)
END
The output can be read back in with the same free-format style. The fields are separated by spaces (outside a quoted string) though commas are also allowed. The file content is as follows:
"jsmith " "x " 1001 1000 "Joe Smith " "Room 1007 " "(234)555-8917 " "(234)555-0077 " "jsmith@rosettacode.org " "/home/jsmith " "/bin/bash " "jdoe " "x " 1002 1000 "Jane Doe " "Room 1004 " "(234)555-8914 " "(234)555-0044 " "jdoe@rosettacode.org " "home/jdoe " "/bin/bash " "xyz " "x " 1003 1000 "X Yz " "Room 1003 " "(234)555-8193 " "(234)555-033 " "xyz@rosettacode.org " "/home/xyz " "/bin/bash "
Numerical values are written with sufficient space to allow for their maximum value, so the sixteen-bit integers are allowed six spaces (in case a minus sign might be needed) and so on for other types. Thus, complex numbers are written in the (real,imaginary) style. Given this fixed layout, an explicit FORMAT statement could be used and delimiters be abandoned along with worry over quoting, but any changes to the data structure will require corresponding changes to the associated FORMAT statement, and mistakes are easily made. For input via free-format, the trailing spaces in the quoted strings could be omitted; any needed will be supplied by the READ process.
To demonstrate that they have been read successfully, the data aggregate is printed out using the NAMELIST protocol, whereby each item in the output list is presented in the form <name> = <value>, as follows:
Record 1 &STUFF NOTE%ACCOUNT = "jsmith ", NOTE%PASSWORD = "x ", NOTE%UID = 1001, NOTE%GID = 1000, NOTE%PERSON%FULLNAME = "Joe Smith ", NOTE%PERSON%OFFICE = "Room 1007 ", NOTE%PERSON%EXTENSION = "(234)555-8917 ", NOTE%PERSON%HOMEPHONE = "(234)555-0077 ", NOTE%PERSON%EMAIL = "jsmith@rosettacode.org ", NOTE%DIRECTORY = "/home/jsmith ", NOTE%SHELL = "/bin/bash " / Record 2 &STUFF NOTE%ACCOUNT = "jdoe ", NOTE%PASSWORD = "x ", NOTE%UID = 1002, NOTE%GID = 1000, NOTE%PERSON%FULLNAME = "Jane Doe ", NOTE%PERSON%OFFICE = "Room 1004 ", NOTE%PERSON%EXTENSION = "(234)555-8914 ", NOTE%PERSON%HOMEPHONE = "(234)555-0044 ", NOTE%PERSON%EMAIL = "jdoe@rosettacode.org ", NOTE%DIRECTORY = "home/jdoe ", NOTE%SHELL = "/bin/bash " / Record 3 &STUFF NOTE%ACCOUNT = "xyz ", NOTE%PASSWORD = "x ", NOTE%UID = 1003, NOTE%GID = 1000, NOTE%PERSON%FULLNAME = "X Yz ", NOTE%PERSON%OFFICE = "Room 1003 ", NOTE%PERSON%EXTENSION = "(234)555-8193 ", NOTE%PERSON%HOMEPHONE = "(234)555-033 ", NOTE%PERSON%EMAIL = "xyz@rosettacode.org ", NOTE%DIRECTORY = "/home/xyz ", NOTE%SHELL = "/bin/bash " /
Because the output file (MSG) was opened with DELIM="QUOTE", the text variables are presented enquoted. This makes it clear whether fields have leading spaces or not, which with the usual proportionally-spaced typefaces and .html rendering is not clear in the example and could cause serious difficulty in practice as between "Joe Bloggs" and " Joe Bloggs". Because the DELIM feature applies to both free-format and namelist output, WRITE (MSG,*) "Record",N would produce output with the text "Record" in quotes, so instead a suitable FORMAT statement is used. Alas, for compound names the % symbol is used instead of a period, a pity. NAMELIST style I/O starts with "&STUFF" (the name of the NAMELIST) and ends with "/" and like free-format output, starts each line with a space that would be consumed as a carriage-control character for lineprinter output.
The "append" to a file is available only if the ACCESS="APPEND" facility is available, and alas, this is not standard Fortran though a common extension. Files opened for output are exclusive use. If a file exists but is in use, the OPEN statement will fail, so one should include the ERR=label,IOSTAT=WHAT to attempt to recover from lockouts. Except that IOSTAT error codes for a given problem may well vary from one system to another.
FreeBASIC
' FB 1.05.0 Win64
Type Person
As String fullname
As String office
As String extension
As String homephone
As String email
Declare Constructor()
Declare Constructor(As String, As String, As String, As String, As String)
Declare Operator Cast() As String
End Type
Constructor Person()
End Constructor
Constructor Person(fullname As String, office As String, extension As String, _
homephone As String, email As String)
With This
.fullname = fullname
.office = office
.extension = extension
.homephone = homephone
.email = email
End With
End Constructor
Operator Person.Cast() As String
Return fullname + "," + office + "," + extension + "," + homephone + "," + email
End Operator
Type Record
As String account
As String password
As Integer uid
As Integer gid
As Person user
As String directory
As String shell
Declare Constructor()
Declare Constructor(As String, As String, As Integer, As Integer, As Person, As String, As String)
Declare Operator Cast() As String
End Type
Constructor Record()
End Constructor
Constructor Record(account As String, password As String, uid As Integer, gid As Integer, user As Person, _
directory As String, shell As String)
With This
.account = account
.password = password
.uid = uid
.gid = gid
.user = user
.directory = directory
.shell = shell
End With
End Constructor
Operator Record.Cast() As String
Return account + ":" + password + ":" + Str(uid) + ":" + Str(gid) + ":" + user + ":" + directory + ":" + shell
End Operator
Dim persons(1 To 3) As Person
persons(1) = Person("Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org")
persons(2) = Person("Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org" )
persons(3) = Person("X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org" )
Dim records(1 To 3) As Record
records(1) = Record("jsmith", "x", 1001, 1000, persons(1), "/home/jsmith", "/bin/bash")
records(2) = Record("jdoe", "x", 1002, 1000, persons(2), "/home/jdoe" , "/bin/bash")
records(3) = Record("xyz", "x", 1003, 1000, persons(3), "/home/xyz" , "/bin/bash")
Open "passwd.txt" For Output As #1
Print #1, records(1)
Print #1, records(2)
Close #1
Open "passwd.txt" For Append Lock Write As #1
Print #1, records(3)
Close #1
- Output:
' contents of passwd.txt after appending the third record jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| FB Type | CSV text file | FB Standard Library | ☑ | ☑ | ☑ (Hopefully!) |
Free Pascal
See also Pascal
{$mode objFPC}
{$longStrings on}
{$modeSwitch classicProcVars+}
uses
cTypes,
// for system call wrappers
unix;
const
passwdPath = '/tmp/passwd';
resourceString
advisoryLockFailed = 'Error: could not obtain advisory lock';
type
GECOS = object
fullname: string;
office: string;
extension: string;
homephone: string;
email: string;
function asString: string;
end;
entry = object
account: string;
password: string;
UID: cUInt;
GID: cUInt;
comment: GECOS;
directory: string;
shell: string;
function asString: string;
end;
function GECOS.asString: string;
const
separator = ',';
begin
with self do
begin
writeStr(result, fullname, separator, office, separator, extension,
separator, homephone, separator, email);
end;
end;
function entry.asString: string;
const
separator = ':';
begin
with self do
begin
writeStr(result, account, separator, password, separator, UID:1,
separator, GID:1, separator, comment.asString, separator, directory,
separator, shell);
end;
end;
procedure writeEntry(var f: text; const value: entry);
begin
writeLn(f, value.asString);
end;
procedure appendEntry(var f: text; const value: entry);
begin
// (re-)open for writing and immediately seek to EOF
append(f);
writeEntry(f, value);
end;
// === MAIN ==============================================================
var
passwd: text;
procedure releaseLock;
begin
// equivalent to `exitCode := exitCode + …`
inc(exitCode, fpFLock(passwd, lock_un));
end;
var
user: entry;
line: string;
begin
assign(passwd, passwdPath);
// open for reading
reset(passwd);
if fpFLock(passwd, lock_ex or lock_NB) <> 0 then
begin
writeLn(stdErr, advisoryLockFailed);
halt(1);
end;
addExitProc(releaseLock);
// reopen for _over_writing: immediately sets file size to 0
rewrite(passwd);
user.account := 'jsmith';
user.password := 'x';
user.UID := 1001;
user.GID := 1000;
user.comment.fullname := 'Joe Smith';
user.comment.office := 'Room 1007';
user.comment.extension := '(234)555-8917';
user.comment.homephone := '(234)555-0077';
user.comment.email := 'jsmith@rosettacode.org';
user.directory := '/home/jsmith';
user.shell := '/bin/bash';
appendEntry(passwd, user);
with user do
begin
account := 'jdoe';
password := 'x';
UID := 1002;
GID := 1000;
with comment do
begin
fullname := 'Jane Doe';
office := 'Room 1004';
extension := '(234)555-8914';
homephone := '(234)555-0044';
email := 'jdoe@rosettacode.org';
end;
directory := '/home/jdoe';
shell := '/bin/bash';
end;
appendEntry(passwd, user);
// Close the file, ...
close(passwd);
with user, user.comment do
begin
account := 'xyz';
UID := 1003;
fullname := 'X Yz';
office := 'Room 1003';
extension := '(234)555-8913';
homephone := '(234)555-0033';
email := 'xyz@rosettacode.org';
directory := '/home/xyz';
end;
// ... then reopen the file for append.
appendEntry(passwd, user);
// open the file and demonstrate the new record has indeed written to the end
reset(passwd);
while not EOF(passwd) do
begin
readLn(passwd, line);
writeLn(line);
end;
end.
- Output:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| record | ASCII text | default RTL | ☑ | ☐ | ☐ |
FutureBasic
local fn AppendRecordToFile( pwStr as CFStringRef, url as CFURLRef ) as BOOL
ErrorRef err = NULL
BOOL success = YES
CFDataRef pwData = fn StringData( pwStr, NSUTF8StringEncoding )
FileHandleRef fh = fn FileHandleForWritingToURL( url, @err )
if ( err )
success = fn FileManagerFileExistsAtURL( url )
if success == NO then fn FileManagerCreateFileAtURL( url, pwData, NULL ) : success = YES : exit fn
end if
success = fn FileHandleSeekToEnd( fh, NULL, @err )
if success == NO then print fn ErrorLocalizedDescription( err ) : exit fn
success = fn FileHandleWriteData( fh, pwData, @err )
if success == NO then print fn ErrorLocalizedDescription( err ) : exit fn
success = fn FileHandleClose( fh, @err )
if success == NO then print fn ErrorLocalizedDescription( err ) : exit fn
end fn = success
local fn ReadFileRecords( url as CFURLRef )
ErrorRef err = NULL
CFDataRef pwData = fn DataWithContentsOfURL( url, NSDataReadingMappedIfSafe, @err )
if err then print fn ErrorLocalizedDescription( err ) : exit fn
print fn StringWithData( pwData, NSUTF8StringEncoding )
end fn
local fn ProcessRecords
BOOL success = NO
CFURLRef desktopURL = fn FileManagerURLForDirectory( NSDesktopDirectory, NSUserDomainMask )
CFURLRef url = fn URLByAppendingPathComponent( desktopURL, @"passwords.txt" )
CFArrayRef pwRecords = @[@"account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell\n",¬
@"jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash\n",¬
@"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash\n"]
NSUInteger i, count = len(pwRecords)
for i = 0 to count - 1
success = fn AppendRecordToFile( pwRecords[i], url )
if success then printf @"Record appended to file." else printf @"Failed to append record."
next
fn ReadFileRecords( url )
end fn
fn ProcessRecords
HandleEvents- Output:
Record appended to file. Record appended to file. Record appended to file. account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash
Go
package main
import (
"bytes"
"fmt"
"io"
"io/ioutil"
"os"
)
type pw struct {
account, password string
uid, gid uint
gecos
directory, shell string
}
type gecos struct {
fullname, office, extension, homephone, email string
}
func (p *pw) encode(w io.Writer) (int, error) {
return fmt.Fprintf(w, "%s:%s:%d:%d:%s,%s,%s,%s,%s:%s:%s\n",
p.account, p.password, p.uid, p.gid,
p.fullname, p.office, p.extension, p.homephone, p.email,
p.directory, p.shell)
}
// data cut and pasted from task description
var p2 = []pw{
{"jsmith", "x", 1001, 1000, gecos{"Joe Smith", "Room 1007",
"(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org"},
"/home/jsmith", "/bin/bash"},
{"jdoe", "x", 1002, 1000, gecos{"Jane Doe", "Room 1004",
"(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org"},
"/home/jsmith", "/bin/bash"},
}
var pa = pw{"xyz", "x", 1003, 1000, gecos{"X Yz", "Room 1003",
"(234)555-8913", "(234)555-0033", "xyz@rosettacode.org"},
"/home/xyz", "/bin/bash"}
var expected = "xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913," +
"(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash"
const pfn = "mythical"
func main() {
writeTwo()
appendOneMore()
checkResult()
}
func writeTwo() {
// overwrites any existing file
f, err := os.Create(pfn)
if err != nil {
fmt.Println(err)
return
}
defer func() {
if cErr := f.Close(); cErr != nil && err == nil {
fmt.Println(cErr)
}
}()
for _, p := range p2 {
if _, err = p.encode(f); err != nil {
fmt.Println(err)
return
}
}
}
func appendOneMore() {
// file must already exist
f, err := os.OpenFile(pfn, os.O_RDWR|os.O_APPEND, 0)
if err != nil {
fmt.Println(err)
return
}
if _, err := pa.encode(f); err != nil {
fmt.Println(err)
}
if cErr := f.Close(); cErr != nil && err == nil {
fmt.Println(cErr)
}
}
func checkResult() {
// reads entire file then closes it
b, err := ioutil.ReadFile(pfn)
if err != nil {
fmt.Println(err)
return
}
if string(bytes.Split(b, []byte{'\n'})[2]) == expected {
fmt.Println("append okay")
} else {
fmt.Println("it didn't work")
}
}
- Output:
append okay
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Byte slice. See note 1. | Abstracted. See note 2. | Go standard library. See note 3. | Yes | No. See note 4. | Should be, but see note 5. |
Notes:
- Data arguments for basic IO functions are type []byte. All data being written ultimately gets encoded to []byte. Some higher level functions accept strings and do the conversion as a convenience. The fmt.Fprintf function used in this task encodes basic types directly to an io.Writer. Some packages such as json and xml have marshallers to encode more complex data structures. These features are common to all writes and are not specific to append.
- The device data representation is abstracted by the type os.File and its associated functions and methods. These methods include seeking by linear file position so a typical data representation is mappable to a linear sequence of bytes. That is about all that can be concluded from the capabilites of the os.File type. This linear nature is not specific to append.
- Go's os package provides high-level services which work reasonably the same across all supported operating systems. Currently the list is darwin, freebsd, linux, netbsd, openbsd, windows. It does this with a common OS-independent interface. Operations which cannot be offered accross all operating systems are not in this package. Additional low-level and operating system specific functions are provided in the syscall package. This organization is not specific to append.
- The file position after opening a file is 0 unless os.O_APPEND is specified in the os.OpenFile function.
- The Go documentation says nothing about file operations by multiple concurrent processes or threads. As the operations are expected to work the same across operating systems however, they presumably do what you would expect. It seems os.FileOpen with os.O_RDWR for example, gives exclusive file access (on local file systems anyway) whether os.O_APPEND is specified or not.
Groovy
Solution:
class PasswdRecord {
String account, password, directory, shell
int uid, gid
SourceRecord source
private static final fs = ':'
private static final fieldNames = ['account', 'password', 'uid', 'gid', 'source', 'directory', 'shell']
private static final stringFields = ['account', 'password', 'directory', 'shell']
private static final intFields = ['uid', 'gid']
PasswdRecord(String line = null) {
if (!line) return
def fields = line.split(fs)
if (fields.size() != fieldNames.size()) {
throw new IllegalArgumentException(
"Passwd record must have exactly ${fieldNames.size()} '${fs}'-delimited fields")
}
(0..<fields.size()).each { i ->
switch (fieldNames[i]) {
case stringFields: this[fieldNames[i]] = fields[i]; break
case intFields: this[fieldNames[i]] = fields[i] as Integer; break
default /* source */: this.source = new SourceRecord(fields[i]); break
}
}
}
@Override String toString() { fieldNames.collect { "${this[it]}${fs}" }.sum()[0..-2] }
}
class SourceRecord {
String fullname, office, extension, homephone, email
private static final fs = ','
private static final fieldNames =
['fullname', 'office', 'extension', 'homephone', 'email']
SourceRecord(String line = null) {
if (!line) return
def fields = line.split(fs)
if (fields.size() != fieldNames.size()) {
throw new IllegalArgumentException(
"Source record must have exactly ${fieldNames.size()} '${fs}'-delimited fields")
}
(0..<fields.size()).each { i ->
this[fieldNames[i]] = fields[i]
}
}
@Override String toString() { fieldNames.collect { "${this[it]}${fs}" }.sum()[0..-2] }
}
def appendNewPasswdRecord = {
PasswdRecord pwr = new PasswdRecord().with { p ->
(account, password, uid, gid) = ['xyz', 'x', 1003, 1000]
source = new SourceRecord().with { s ->
(fullname, office, extension, homephone, email) =
['X Yz', 'Room 1003', '(234)555-8913', '(234)555-0033', 'xyz@rosettacode.org']
s
}
(directory, shell) = ['/home/xyz', '/bin/bash']
p
};
new File('passwd.txt').withWriterAppend { w ->
w.append(pwr as String)
w.append('\r\n')
}
}
Test:
def checkPasswdFile = { it ->
File passwd = new File('passwd.txt')
assert passwd.exists()
passwd.eachLine { line ->
def pw = new PasswdRecord(line)
assert pw && pw instanceof PasswdRecord
assert pw.source && pw.source instanceof SourceRecord
println pw
}
println()
}
println "File contents before new record added"
checkPasswdFile()
appendNewPasswdRecord()
println "File contents after new record added"
checkPasswdFile()
Output:
File contents before new record added jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jsmith:/bin/bash File contents after new record added jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jsmith:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Haskell
Solution:
{-# LANGUAGE RecordWildCards #-}
import System.IO
import Data.List (intercalate)
data Gecos = Gecos { fullname :: String
, office :: String
, extension :: String
, homephone :: String
, email :: String
}
data Record = Record { account :: String
, password :: String
, uid :: Int
, gid :: Int
, directory :: String
, shell :: String
, gecos :: Gecos
}
instance Show Gecos where
show (Gecos {..}) = intercalate "," [fullname, office, extension, homephone, email]
instance Show Record where
show (Record {..}) = intercalate ":" [account, password, show uid, show gid, show gecos, directory, shell]
addRecord :: String -> Record -> IO ()
addRecord path r = appendFile path (show r)
Test:
t1 = Record "jsmith" "x" 1001 1000 "/home/jsmith" "/bin/bash"
(Gecos "Joe Smith" "Room 1007" "(234)555-8917" "(234)555-0077" "jsmith@rosettacode.org")
t2 = Record "jdoe" "x" 1002 1000 "/home/jdoe" "/bin/bash"
(Gecos "Jane Doe" "Room 1004" "(234)555-8914" "(234)555-0044" "jdoe@rosettacode.org")
t3 = Record "xyz" "x" 1003 1000 "/home/xyz" "/bin/bash"
(Gecos "X Yz" "Room 1003" "(234)555-8913" "(234)555-0033" "xyz@rosettacode.org")
main = do
let path = "test.txt"
forM [t1,t2,t3] (addRecord path)
lastLine <- fmap (last . lines) (readFile path)
putStrLn lastLine
Icon and Unicon
Works in both languages:
procedure main()
orig := [
"jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash",
"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jsmith:/bin/bash"
]
new := [
"xyz:x:1003:1000:X:Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash"
]
fName := !open("mktemp","rp")
every (f := open(fName,"w")) | write(f,!orig) | close(f)
every (f := open(fName,"a")) | write(f,!new) | close(f)
every (f := open(fName,"r")) | write(!f) | close(f)
end
Run:
->arteotf jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jsmith:/bin/bash xyz:x:1003:1000:X:Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash ->
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| String | String | built-in | ☑ | ☑ | ☑ (Not all, eg NFS) |
J
require'strings ~system/packages/misc/xenos.ijs'
record=: [:|: <@deb;._1@(':',]);._2@do bind '0 :0'
passfields=: <;._1':username:password:gid:uid:gecos:home:shell'
passrec=: LF,~ [: }.@;@ , ':';"0 (passfields i. {. ) { a:,~ {:
R1=: passrec record''
username: jsmith
password: x
gid: 1001
uid: 1000
gecos: Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org
home: /home/jsmith
shell: /bin/bash
)
R2=: passrec record''
username: jdoe
password: x
gid: 1002
uid: 1000
gecos: Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org
home: /home/jdoe
shell: /bin/bash
)
R3=: passrec record''
username: xyz
password: x
gid: 1003
uid: 1000
gecos: X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org
home: /home/xyz
shell: /bin/bash
)
passwd=: <'/tmp/passwd.txt' NB. file needs to be writable on implementation machine
(R1,R2) fwrite passwd
R3 fappend passwd
assert 1 e. R3 E. fread passwd
| Data Representation | |
|---|---|
| In core | On disk |
| array | literal |
Note that no file locking is needed if this is implemented under windows (since all file writes are atomic across processes -- only one process can have a file open at one time, by default). Note that file locking would be needed under Linux (or unix), but it's not clear which file locking mechanism should be used.
Java
import java.io.FileOutputStream;
import java.io.IOException;
void append(String path, byte[] data) throws IOException {
/* the second argument here is for appending bytes */
try (FileOutputStream output = new FileOutputStream(path, true)) {
output.write(data);
}
}
An alternate implementation.
import static java.util.Objects.requireNonNull;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class RecordAppender {
static class Record {
private final String account;
private final String password;
private final int uid;
private final int gid;
private final List<String> gecos;
private final String directory;
private final String shell;
public Record(String account, String password, int uid, int gid, List<String> gecos, String directory, String shell) {
this.account = requireNonNull(account);
this.password = requireNonNull(password);
this.uid = uid;
this.gid = gid;
this.gecos = requireNonNull(gecos);
this.directory = requireNonNull(directory);
this.shell = requireNonNull(shell);
}
@Override
public String toString() {
return account + ':' + password + ':' + uid + ':' + gid + ':' + String.join(",", gecos) + ':' + directory + ':' + shell;
}
public static Record parse(String text) {
String[] tokens = text.split(":");
return new Record(
tokens[0],
tokens[1],
Integer.parseInt(tokens[2]),
Integer.parseInt(tokens[3]),
Arrays.asList(tokens[4].split(",")),
tokens[5],
tokens[6]);
}
}
public static void main(String[] args) throws IOException {
List<String> rawData = Arrays.asList(
"jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,[email protected]:/home/jsmith:/bin/bash",
"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/home/jdoe:/bin/bash",
"xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,[email protected]:/home/xyz:/bin/bash"
);
List<Record> records = rawData.stream().map(Record::parse).collect(Collectors.toList());
Path tmp = Paths.get("_rosetta", ".passwd");
Files.createDirectories(tmp.getParent());
Files.write(tmp, (Iterable<String>) records.stream().limit(2).map(Record::toString)::iterator);
Files.write(tmp, Collections.singletonList(records.get(2).toString()), StandardOpenOption.APPEND);
try (Stream<String> lines = Files.lines(tmp)) {
lines.map(Record::parse).forEach(System.out::println);
}
}
}
- Output:
Appended Record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Julia
using SHA # security instincts say do not write bare passwords to a shared file even in toy code :)
mutable struct Personnel
fullname::String
office::String
extension::String
homephone::String
email::String
Personnel(ful,off,ext,hom,ema) = new(ful,off,ext,hom,ema)
end
mutable struct Passwd
account::String
password::String
uid::Int32
gid::Int32
personal::Personnel
directory::String
shell::String
Passwd(acc,pas,uid,gid,per,dir,she) = new(acc,pas,uid,gid,per,dir,she)
end
function writepasswd(filename, passrecords)
if(passrecords isa Array) == false
passrecords = [passrecords]
end
fh = open(filename, "a") # should throw an exception if cannot open in a locked or exclusive mode for append
for pas in passrecords
record = join([pas.account, bytes2hex(sha256(pas.password)), pas.uid, pas.gid,
join([pas.personal.fullname, pas.personal.office, pas.personal.extension,
pas.personal.homephone, pas.personal.email], ','),
pas.directory, pas.shell], ':')
write(fh, record, "\n")
end
close(fh)
end
const jsmith = Passwd("jsmith","x",1001, 1000, Personnel("Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org"), "/home/jsmith", "/bin/bash")
const jdoe = Passwd("jdoe","x",1002, 1000, Personnel("Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org"), "/home/jdoe", "/bin/bash")
const xyz = Passwd("xyz","x",1003, 1000, Personnel("X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org"), "/home/xyz", "/bin/bash")
const pfile = "pfile.csv"
writepasswd(pfile, [jsmith, jdoe])
println("Before last record added, file is:\n$(readstring(pfile))")
writepasswd(pfile, xyz)
println("After last record added, file is:\n$(readstring(pfile))")
- Output:
Before last record added, file is: jsmith:2d711642b726b04401627ca9fbac32f5c8530fb1903cc4db02258717921a4881:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:2d711642b726b04401627ca9fbac32f5c8530fb1903cc4db02258717921a4881:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash
After last record added, file is: jsmith:2d711642b726b04401627ca9fbac32f5c8530fb1903cc4db02258717921a4881:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:2d711642b726b04401627ca9fbac32f5c8530fb1903cc4db02258717921a4881:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:2d711642b726b04401627ca9fbac32f5c8530fb1903cc4db02258717921a4881:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Kotlin
// Version 1.2.41
import java.io.File
class Record(
val account: String,
val password: String,
val uid: Int,
val gid: Int,
val gecos: List<String>,
val directory: String,
val shell: String
){
override fun toString() =
"$account:$password:$uid:$gid:${gecos.joinToString(",")}:$directory:$shell"
}
fun parseRecord(line: String): Record {
val fields = line.split(':')
return Record(
fields[0],
fields[1],
fields[2].toInt(),
fields[3].toInt(),
fields[4].split(','),
fields[5],
fields[6]
)
}
fun main(args: Array<String>) {
val startData = listOf(
"jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,[email protected]:/home/jsmith:/bin/bash",
"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/home/jdoe:/bin/bash"
)
val records = startData.map { parseRecord(it) }
val f = File("passwd.csv")
f.printWriter().use {
for (record in records) it.println(record)
}
println("Initial records:\n")
f.forEachLine {
println(parseRecord(it))
}
val newData = "xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,[email protected]:/home/xyz:/bin/bash"
val record = parseRecord(newData)
if (!f.setWritable(true, true)) {
println("\nFailed to make file writable only by owner\n.")
}
f.appendText("$record\n")
println("\nRecords after another one is appended:\n")
f.forEachLine {
println(parseRecord(it))
}
}
- Output:
Initial records: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,[email protected]:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/home/jdoe:/bin/bash Records after another one is appended: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,[email protected]:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,[email protected]:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Class | Text file | JDK | ☑ | ☑ | ☑ (System dependent) |
Lua
function append(tbl,filename)
local file,err = io.open(filename, "a")
if err then return err end
file:write(tbl.account..":")
file:write(tbl.password..":")
file:write(tbl.uid..":")
file:write(tbl.gid..":")
for i,v in ipairs(tbl.gecos) do
if i>1 then
file:write(",")
end
file:write(v)
end
file:write(":")
file:write(tbl.directory..":")
file:write(tbl.shell.."\n")
file:close()
end
local smith = {}
smith.account = "jsmith"
smith.password = "x"
smith.uid = 1001
smith.gid = 1000
smith.gecos = {"Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org"}
smith.directory = "/home/jsmith"
smith.shell = "/bin/bash"
append(smith, ".passwd")
local doe = {}
doe.account = "jdoe"
doe.password = "x"
doe.uid = 1002
doe.gid = 1000
doe.gecos = {"Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org"}
doe.directory = "/home/jdoe"
doe.shell = "/bin/bash"
append(doe, ".passwd")
local xyz = {}
xyz.account = "xyz"
xyz.password = "x"
xyz.uid = 1003
xyz.gid = 1000
xyz.gecos = {"X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org"}
xyz.directory = "/home/xyz"
xyz.shell = "/bin/bash"
append(xyz, ".passwd")
M2000 Interpreter
Module TestThis {
Class passwd {
account$, password$
UID, GID
group GECOS {
fullname$,office$,extension$,homephone$,email$
function Line$() {
=format$("{0},{1} {2},{3},{4}", .fullname$,.office$,.extension$,.homephone$,.email$)
}
}
directory$, shell$
Function Line$() {
=format$("{0}:{1}:{2}:{3}:{4}:{5}:{6}",.account$,.password$, .UID, .GID, .GECOS.Line$(), .directory$, .shell$)
}
class:
Module passwd {
if match("SSNNSSSSSSS") then
Read .account$, .password$
Read .UID, .GID
For .GECOS {
Read .fullname$,.office$,.extension$,.homephone$,.email$
}
Read .directory$, .shell$
Else.If Match("S") then
Dim a$(), b$()
a$()=Piece$(letter$, ":")
.account$<=a$(0)
.password$<=a$(1)
.UID<=Val(a$(2))
.GID<=Val(a$(3))
For .GECOS {
b$()=Piece$(a$(4), ",")
.fullname$<=b$(0)
.office$<=Piece$(b$(1), " ")(0)
.extension$<=Piece$(b$(1), " ")(1)
.homephone$<=b$(2)
.email$<=b$(3)
}
.directory$<=a$(5)
.shell$<=a$(6)
End if
}
}
Flush
Data PASSWD("jsmith", "x", 1001, 1000, "Joe Smith", "Room", "1007","(234)555-8917","(234)555-0077","jsmith@rosettacode.org","/home/jsmith","/bin/bash")
Data PASSWD("jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044:jdoe@rosettacode.org:/home/jdoe")
\\ we have to make the file if not exist before we use APPEND
if not exist("passwd") then
Open "passwd" for Output as #F
Close #F
end if
Open "passwd" for wide append as #F
While not empty
read A
Print #F, A.Line$()
End While
Close #F
Ret=PASSWD("xyz","x",1003,1000,"X Yz", "Room", "1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org","/home/xyz","/bin/bash")
Repeat
Try ok {
Open "passwd" for wide append exclusive as F
Print #F, Ret.Line$()
close #F
}
Until Not (Error or Not ok)
I=1
Document Ret$
Open "passwd" for wide input as #F
While not Eof(#F)
Line Input #F, record$
Ret$=Format$("{0}|{1}",Str$(I,"0000"),Record$)+{
}
I++
End While
Close #F
ClipBoard Ret$
Report Ret$
}
TestThis- Output:
0001|jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077:jsmith@rosettacode.org:/home/jsmith 0002|jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044:jdoe@rosettacode.org:/home/jdoe 0003|xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033:xyz@rosettacode.org:/home/xyz
Mathematica / Wolfram Language
data = <|"account" -> "xyz", "password" -> "x", "UID" -> 1003,
"GID" -> 1000, "fullname" -> "X Yz", "office" -> "Room 1003",
"extension" -> "(234)555-8913", "homephone" -> "(234)555-0033",
"email" -> "xyz@rosettacode.org", "directory" -> "/home/xyz",
"shell" -> "/bin/bash"|>;
asString[data_] :=
StringRiffle[
ToString /@
Insert[data /@ {"account", "password", "UID", "GID", "directory",
"shell"},
StringRiffle[
data /@ {"fullname", "office", "extension", "homephone",
"email"}, ","], 5], ":"];
fname = FileNameJoin[{$TemporaryDirectory, "testfile"}];
str = OpenWrite[fname]; (* Use OpenAppend if file exists *)
Close[str];
Print["Appended record: " <> asString[data]];
- Output:
Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Association | Nearly anything | Standard Library | ☑ | ☑ | ☐ |
MATLAB / Octave
DS{1}.account='jsmith';
DS{1}.password='x';
DS{1}.UID=1001;
DS{1}.GID=1000;
DS{1}.fullname='Joe Smith';
DS{1}.office='Room 1007';
DS{1}.extension='(234)555-8917';
DS{1}.homephone='(234)555-0077';
DS{1}.email='jsmith@rosettacode.org';
DS{1}.directory='/home/jsmith';
DS{1}.shell='/bin/bash';
DS{2}.account='jdoe';
DS{2}.password='x';
DS{2}.UID=1002;
DS{2}.GID=1000;
DS{2}.fullname='Jane Doe';
DS{2}.office='Room 1004';
DS{2}.extension='(234)555-8914';
DS{2}.homephone='(234)555-0044';
DS{2}.email='jdoe@rosettacode.org';
DS{2}.directory='/home/jdoe';
DS{2}.shell='/bin/bash';
function WriteRecord(fid, rec)
fprintf(fid,"%s:%s:%i:%i:%s,%s,%s,%s,%s:%s%s\n", rec.account, rec.password, rec.UID, rec.GID, rec.fullname, rec.office, rec.extension, rec.homephone, rec.email, rec.directory, rec.shell);
return;
end
%% write
fid = fopen('passwd.txt','w');
WriteRecord(fid,DS{1});
WriteRecord(fid,DS{2});
fclose(fid);
new.account='xyz';
new.password='x';
new.UID=1003;
new.GID=1000;
new.fullname='X Yz';
new.office='Room 1003';
new.extension='(234)555-8913';
new.homephone='(234)555-0033';
new.email='xyz@rosettacode.org';
new.directory='/home/xyz';
new.shell='/bin/bash';
%% append
fid = fopen('passwd.txt','a+');
WriteRecord(fid,new);
fclose(fid);
% read password file
fid = fopen('passwd.txt','r');
while ~feof(fid)
printf('%s\n',fgetl(fid));
end;
fclose(fid);
- Output:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz/bin/bash
Nim
This solution defines a procedure "getlock" which try the get an exclusive (write) lock on the file. On Posix systems, the standard Posix advisory locking mechanism, which works at process level, is used. On other systems, especially Windows, the procedure does nothing and returns true as there is no need for such a mechanism.
Note that on Posix system, other programs may still write on the file if they do not check if an exclusive lock is already set on the file.
As several other solutions, we have chosen to parse the "passwd" lines even if it not required.
import posix
import strutils
type
# GECOS representation.
Gecos = tuple[fullname, office, extension, homephone, email: string]
# Record representation.
Record = object
account: string
password: string
uid: int
gid: int
gecos: Gecos
directory: string
shell: string
#---------------------------------------------------------------------------------------------------
proc str(gecos: Gecos): string =
## Explicit representation of a GECOS.
result = "("
for name, field in gecos.fieldPairs:
result.addSep(", ", 1)
result.add(name & ": " & field)
result.add(')')
#---------------------------------------------------------------------------------------------------
proc `$`(gecos: Gecos): string =
## Compact representation of a GECOS.
for field in gecos.fields:
result.addSep(",", 0)
result.add(field)
#---------------------------------------------------------------------------------------------------
proc parseGecos(s: string): Gecos =
## Parse a string and return a Gecos tuple.
let fields = s.split(",")
result = (fields[0], fields[1], fields[2], fields[3], fields[4])
#---------------------------------------------------------------------------------------------------
proc str(rec: Record): string =
## Explicit representation of a record.
for name, field in rec.fieldPairs:
result.add(name & ": ")
when typeof(field) is Gecos:
result.add(str(field))
else:
result.add($field)
result.add('\n')
#---------------------------------------------------------------------------------------------------
proc `$`(rec: Record): string =
# Compact representation fo a record.
for field in rec.fields:
result.addSep(":", 0)
result.add($field)
#---------------------------------------------------------------------------------------------------
proc parseRecord(line: string): Record =
## Parse a string and return a Record object.
let fields = line.split(":")
result.account = fields[0]
result.password = fields[1]
result.uid = fields[2].parseInt()
result.gid = fields[3].parseInt()
result.gecos = parseGecos(fields[4])
result.directory = fields[5]
result.shell = fields[6]
#---------------------------------------------------------------------------------------------------
proc getLock(f: File): bool =
## Try to get an exclusive write lock on file "f". Return false is unsuccessful.
when defined(posix):
var flock = TFlock(l_type: cshort(F_WRLCK), l_whence: cshort(SEEK_SET), l_start: 0, l_len: 0)
result = f.getFileHandle().fcntl(F_SETLK, flock.addr) >= 0
else:
result = true
#———————————————————————————————————————————————————————————————————————————————————————————————————
var pwfile: File
const Filename = "passwd"
const Data = ["jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash",
"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash"]
# Prepare initial file.
# We don'’t use a lock here as it is only the preparation.
pwfile = open(FileName, fmWrite)
for line in Data:
pwfile.writeLine(line)
pwfile.close()
# Display initial contents.
echo "Raw content of initial password file:"
echo "-------------------------------------"
var records: seq[Record]
for line in lines(FileName):
echo line
records.add(line.parseRecord())
echo ""
echo "Structured content of initial password file:"
echo "--------------------------------------------"
for rec in records:
echo str(rec)
# Add a new record at the end of password file.
pwfile = open(Filename, fmAppend)
let newRecord = Record(account: "xyz",
password: "x",
uid: 1003,
gid: 1000,
gecos: ("X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org"),
directory: "/home/xyz",
shell: "/bin/bash")
echo "Appending new record:"
echo "---------------------"
echo str(newRecord)
if pwfile.getLock():
pwFile.writeLine(newRecord)
pwfile.close()
else:
echo "File is locked. Quitting."
pwFile.close()
quit(QuitFailure)
# Reopen the file and display its contents.
echo "Raw content of updated password file:"
echo "-------------------------------------"
for line in lines(FileName):
echo line
- Output:
Raw content of initial password file: ------------------------------------- jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash Structured content of initial password file: -------------------------------------------- account: jsmith password: x uid: 1001 gid: 1000 gecos: (fullname: Joe Smith, office: Room 1007, extension: (234)555-8917, homephone: (234)555-0077, email: jsmith@rosettacode.org) directory: /home/jsmith shell: /bin/bash account: jdoe password: x uid: 1002 gid: 1000 gecos: (fullname: Jane Doe, office: Room 1004, extension: (234)555-8914, homephone: (234)555-0044, email: jdoe@rosettacode.org) directory: /home/jdoe shell: /bin/bash Appending new record: --------------------- account: xyz password: x uid: 1003 gid: 1000 gecos: (fullname: X Yz, office: Room 1003, extension: (234)555-8913, homephone: (234)555-0033, email: xyz@rosettacode.org) directory: /home/xyz shell: /bin/bash Raw content of updated password file: ------------------------------------- jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Object/Tuple | Text file | Nim Io | ☑ | ☑ | Window: yes Posix: Advisory lock |
Pascal
See also: Free Pascal
program appendARecordToTheEndOfATextFile;
var
passwd: bindable text;
FD: bindingType;
begin
{ initialize FD }
FD := binding(passwd);
FD.name := '/tmp/passwd';
{ attempt opening file [e.g. effective user has proper privileges?] }
bind(passwd, FD);
{ query binding state of `passwd` }
FD := binding(passwd);
if not FD.bound then
begin
writeLn('Error: could not open ', FD.name);
halt;
end;
{ open for overwriting }
rewrite(passwd);
writeLn(passwd, 'jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash');
writeLn(passwd, 'jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash');
{ close }
unbind(passwd);
{ rebind }
bind(passwd, FD);
FD := binding(passwd);
if not FD.bound then
begin
writeLn('Error: could not reopen ', FD.name);
halt;
end;
{ open in append/writable mode }
extend(passwd);
{ write another record to file }
writeLn(passwd, 'xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash');
end.
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| string literal | ASCII text | language core | ☑ | ☐ | ☐ |
Perl
The program uses flock(2) (or emulation, if flock is not available) to lock the file.
use strict;
use warnings;
use Fcntl qw( :flock SEEK_END );
use constant {
RECORD_FIELDS => [qw( account password UID GID GECOS directory shell )],
GECOS_FIELDS => [qw( fullname office extension homephone email )],
RECORD_SEP => ':',
GECOS_SEP => ',',
PASSWD_FILE => 'passwd.txt',
};
# here's our three records
my $records_to_write = [
{
account => 'jsmith',
password => 'x',
UID => 1001,
GID => 1000,
GECOS => {
fullname => 'John Smith',
office => 'Room 1007',
extension => '(234)555-8917',
homephone => '(234)555-0077',
email => 'jsmith@rosettacode.org',
},
directory => '/home/jsmith',
shell => '/bin/bash',
},
{
account => 'jdoe',
password => 'x',
UID => 1002,
GID => 1000,
GECOS => {
fullname => 'Jane Doe',
office => 'Room 1004',
extension => '(234)555-8914',
homephone => '(234)555-0044',
email => 'jdoe@rosettacode.org',
},
directory => '/home/jdoe',
shell => '/bin/bash',
},
];
my $record_to_append = {
account => 'xyz',
password => 'x',
UID => 1003,
GID => 1000,
GECOS => {
fullname => 'X Yz',
office => 'Room 1003',
extension => '(234)555-8913',
homephone => '(234)555-0033',
email => 'xyz@rosettacode.org',
},
directory => '/home/xyz',
shell => '/bin/bash',
};
sub record_to_string {
my $rec = shift;
my $sep = shift // RECORD_SEP;
my $fields = shift // RECORD_FIELDS;
my @ary;
for my $field (@$fields) {
my $r = $rec->{$field};
die "Field '$field' not found" unless defined $r; # simple sanity check
push @ary, ( $field eq 'GECOS' ? record_to_string( $r, GECOS_SEP, GECOS_FIELDS ) : $r );
}
return join $sep, @ary;
}
sub write_records_to_file {
my $records = shift;
my $filename = shift // PASSWD_FILE;
open my $fh, '>>', $filename or die "Can't open $filename: $!";
flock( $fh, LOCK_EX ) or die "Can't lock $filename: $!";
# if someone appended while we were waiting...
seek( $fh, 0, SEEK_END ) or die "Can't seek $filename: $!" ;
print $fh record_to_string($_), "\n" for @$records;
flock( $fh, LOCK_UN ) or die "Can't unlock $filename: $!";
# note: the file is closed automatically when function returns (and refcount of $fh becomes 0)
}
# write two records to file
write_records_to_file( $records_to_write );
# append one more record to file
write_records_to_file( [$record_to_append] );
# test
{
use Test::Simple tests => 1;
open my $fh, '<', PASSWD_FILE or die "Can't open ", PASSWD_FILE, ": $!";
my @lines = <$fh>;
chomp @lines;
ok(
$lines[-1] eq
'xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash',
"Appended record: $lines[-1]"
);
}
Output:
1..1 ok 1 - Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
File contents:
jsmith:x:1001:1000:John Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Hash table | Text file | PerlIO | ☑ | ☑ | Advisory lock |
Note that flock uses advisory lock; some other program (if it doesn't use flock) can still unexpectedly write to the file.
Phix
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| sequence | text file | builtin | ☑ | ☑ | ☑ (Advisory lock) |
Locking is used to ensure multitasking safety. Note that on Phix, "multitasking" is the kid brother of multithreading, and the calls to task_yield() in the code that follows are there to respect the phix-specific definition of multiple tasks being in the same process, in which case locking does not make any real difference - because there is no task_yield() in a locked state. You can also test the locking when running multiple processes/threads by uncommenting the wait_key() lines.
without js -- (file i/o, sleep, task_yield, wait_key) constant filename = "passwd.txt" integer fn constant rec1 = {"jsmith","x",1001,1000,{"Joe Smith","Room 1007","(234)555-8917","(234)555-0077","jsmith@rosettacode.org"},"/home/jsmith","/bin/bash"}, rec2 = {"jdoe","x",1002,1000,{"Jane Doe","Room 1004","(234)555-8914","(234)555-0044","jdoe@rosettacode.org"},"/home/jdoe","/bin/bash"}, rec3 = {"xyz","x",1003,1000,{"X Yz","Room 1003","(234)555-8913","(234)555-0033","xyz@rosettacode.org"},"/home/xyz","/bin/bash"} function tostring(sequence record) record[3] = sprintf("%d",{record[3]}) record[4] = sprintf("%d",{record[4]}) record[5] = join(record[5],",") record = join(record,":") return record end function procedure wait(string what) ?sprintf("wait (%s)",{what}) sleep(1) task_yield() end procedure if not file_exists(filename) then fn = open(filename,"w") if fn!=-1 then -- (someone else just beat us to it?) printf(fn,"account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell\n") printf(fn,"%s\n",{tostring(rec1)}) printf(fn,"%s\n",{tostring(rec2)}) close(fn) end if end if while 1 do fn = open(filename,"a") if fn!=-1 then exit end if wait("append") end while --?"file open in append mode"; {} = wait_key() while 1 do if lock_file(fn,LOCK_EXCLUSIVE,{}) then exit end if wait("lock") end while --?"file locked"; {} = wait_key() printf(fn,"%s\n",{tostring(rec3)}) unlock_file(fn,{}) close(fn) while 1 do fn = open(filename,"r") if fn!=-1 then exit end if wait("read") end while ?gets(fn) while 1 do object line = gets(fn) if atom(line) then exit end if ?line {line} = scanf(line,"%s:%s:%d:%d:%s:%s:%s\n") line[5] = split(line[5],',') ?line end while close(fn)
- Output:
"account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell\n"
"jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash\n"
{"jsmith","x",1001,1000,{"Joe Smith","Room 1007","(234)555-8917","(234)555-0077","jsmith@rosettacode.org"},"/home/jsmith","/bin/bash"}
"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash\n"
{"jdoe","x",1002,1000,{"Jane Doe","Room 1004","(234)555-8914","(234)555-0044","jdoe@rosettacode.org"},"/home/jdoe","/bin/bash"}
"xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash\n"
{"xyz","x",1003,1000,{"X Yz","Room 1003","(234)555-8913","(234)555-0033","xyz@rosettacode.org"},"/home/xyz","/bin/bash"}
Phixmonti
include ..\Utilitys.pmt
def ltos /# l -- s #/
"" >ps
len for get
string? not if
number? if
tostr
else
ltos
"<ls>:" swap "</ls>" chain chain
endif
endif
ps> swap chain ":" chain >ps
endfor
drop
ps>
enddef
def stol /# s -- l #/
-1 del
":" xplit
"<ls>" find 1 + snip
"</ls>" find snip 1 del
rot len >ps rot ps> set swap chain
enddef
( "jsmith" "x" 1001 1000 ( "Joe Smith" "Room 1007" "(234)555-8917" "(234)555-0077" "jsmith@rosettacode.org" ) "/home/jsmith" "/bin/bash" )
( "jdoe" "x" 1002 1000 ( "Jane Doe" "Room 1004" "(234)555-8914" "(234)555-0044" "jdoe@rosettacode.org" ) "/home/jdoe" "/bin/bash" )
swap
"passwd.txt" var file
file "w" fopen var f
ltos 10 chain f fputs
ltos 10 chain f fputs
f fclose
( "xyz" "x" 1003 1000 ( "X Yz" "Room 1003" "(234)555-8913" "(234)555-0033" "xyz@rosettacode.org" ) "/home/xyz" "/bin/bash" )
file "a" fopen var f
ltos 10 chain f fputs
f fclose
file "r" fopen var f
true while
f fgets number? if
drop false
else
stol ? true
endif
endwhile
f fclose- Output:
["jsmith", "x", "1001", "1000", ["Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org"], "/home/jsmith", "/bin/bash"] ["jdoe", "x", "1002", "1000", ["Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org"], "/home/jdoe", "/bin/bash"] ["xyz", "x", "1003", "1000", ["X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org"], "/home/xyz", "/bin/bash"] === Press any key to exit ===
PHP
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| String, array or stream resource | Nearly anything | built-in | ☑ | ☐ | ☑ |
<?php
$filename = '/tmp/passwd';
$data = array(
'account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell' . PHP_EOL,
'jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash' . PHP_EOL,
'jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash' . PHP_EOL,
);
file_put_contents($filename, $data, LOCK_EX);
echo 'File contents before new record added:', PHP_EOL, file_get_contents($filename), PHP_EOL;
$data = array(
'xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash' . PHP_EOL
);
file_put_contents($filename, $data, FILE_APPEND | LOCK_EX);
echo 'File contents after new record added:', PHP_EOL, file_get_contents($filename), PHP_EOL;
- Output:
File contents before new record added: account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash File contents after new record added: account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
PicoLisp
(setq L '((jsmith x 1001 1000
"Joe Smith,Room 1007,(234)555-8917,\
(234)555-0077,jsmith@rosettacode.org"
/home/jsmith /bin/bash )
(jdoe x 1002 1000
"Jane Doe,Room 1004,(234)555-8914,\
(234)555-0044,jdoe@rosettacode.org"
/home/jsmith /bin/bash ) ) )
(setq A '(xyz x 1003 1000
"X Yz,Room 1003,(234)555-8913,\
(234)555-0033,xyz@rosettacode.org"
/home/xyz /bin/bash ) )
(out "mythical"
(for I L
(prinl (glue ': I)) ) )
(out "+mythical"
(prinl (glue ': A)) )
(in "mythical"
(do 2 (line))
(println
(and
(= "xyz" (pack (till ':)))
(= 3 (lines "mythical") ) ) ) )
(bye)PowerShell
I treated the file as a CSV file without header information. File testing is minimal.
Since PowerShell loves to deal in objects I wrote extra code to better manipilate and display data.
function Test-FileLock
{
Param
(
[parameter(Mandatory=$true)]
[string]
$Path
)
$outFile = New-Object System.IO.FileInfo $Path
if (-not(Test-Path -Path $Path))
{
return $false
}
try
{
$outStream = $outFile.Open([System.IO.FileMode]::Open, [System.IO.FileAccess]::ReadWrite, [System.IO.FileShare]::None)
if ($outStream)
{
$outStream.Close()
}
return $false
}
catch
{
# File is locked by a process.
return $true
}
}
function New-Record
{
Param
(
[string]$Account,
[string]$Password,
[int]$UID,
[int]$GID,
[string]$FullName,
[string]$Office,
[string]$Extension,
[string]$HomePhone,
[string]$Email,
[string]$Directory,
[string]$Shell
)
$GECOS = [PSCustomObject]@{
FullName = $FullName
Office = $Office
Extension = $Extension
HomePhone = $HomePhone
Email = $Email
}
[PSCustomObject]@{
Account = $Account
Password = $Password
UID = $UID
GID = $GID
GECOS = $GECOS
Directory = $Directory
Shell = $Shell
}
}
function Import-File
{
Param
(
[Parameter(Mandatory=$false,
ValueFromPipeline=$true,
ValueFromPipelineByPropertyName=$true)]
[string]
$Path = ".\passwd.txt"
)
if (-not(Test-Path $Path))
{
throw [System.IO.FileNotFoundException]
}
$header = "Account","Password","UID","GID","GECOS","Directory","Shell"
$csv = Import-Csv -Path $Path -Delimiter ":" -Header $header -Encoding ASCII
$csv | ForEach-Object {
New-Record -Account $_.Account `
-Password $_.Password `
-UID $_.UID `
-GID $_.GID `
-FullName $_.GECOS.Split(",")[0] `
-Office $_.GECOS.Split(",")[1] `
-Extension $_.GECOS.Split(",")[2] `
-HomePhone $_.GECOS.Split(",")[3] `
-Email $_.GECOS.Split(",")[4] `
-Directory $_.Directory `
-Shell $_.Shell
}
}
function Export-File
{
[CmdletBinding()]
Param
(
[Parameter(Mandatory=$true,
ValueFromPipeline=$true,
ValueFromPipelineByPropertyName=$true)]
$InputObject,
[Parameter(Mandatory=$false,
ValueFromPipeline=$true,
ValueFromPipelineByPropertyName=$true)]
[string]
$Path = ".\passwd.txt"
)
Begin
{
if (-not(Test-Path $Path))
{
New-Item -Path . -Name $Path -ItemType File | Out-Null
}
[string]$recordString = "{0}:{1}:{2}:{3}:{4}:{5}:{6}"
[string]$gecosString = "{0},{1},{2},{3},{4}"
[string[]]$lines = @()
[string[]]$file = Get-Content $Path
}
Process
{
foreach ($object in $InputObject)
{
$lines += $recordString -f $object.Account,
$object.Password,
$object.UID,
$object.GID,
$($gecosString -f $object.GECOS.FullName,
$object.GECOS.Office,
$object.GECOS.Extension,
$object.GECOS.HomePhone,
$object.GECOS.Email),
$object.Directory,
$object.Shell
}
}
End
{
foreach ($line in $lines)
{
if (-not ($line -in $file))
{
$line | Out-File -FilePath $Path -Encoding ASCII -Append
}
}
}
}
Create record objects.
$records = @()
$records+= New-Record -Account 'jsmith' `
-Password 'x' `
-UID 1001 `
-GID 1000 `
-FullName 'Joe Smith' `
-Office 'Room 1007' `
-Extension '(234)555-8917' `
-HomePhone '(234)555-0077' `
-Email 'jsmith@rosettacode.org' `
-Directory '/home/jsmith' `
-Shell '/bin/bash'
$records+= New-Record -Account 'jdoe' `
-Password 'x' `
-UID 1002 `
-GID 1000 `
-FullName 'Jane Doe' `
-Office 'Room 1004' `
-Extension '(234)555-8914' `
-HomePhone '(234)555-0044' `
-Email 'jdoe@rosettacode.org' `
-Directory '/home/jdoe' `
-Shell '/bin/bash'
Display record objects.
$records | Format-Table -AutoSize
- Output:
Account Password UID GID GECOS Directory Shell
------- -------- --- --- ----- --------- -----
jsmith x 1001 1000 @{FullName=Joe Smith; Office=Room 1007; Extension=(234)555-8917; HomePhone=(234)555-0077; Email=jsmith@rosettacode.org} /home/jsmith /bin/bash
jdoe x 1002 1000 @{FullName=Jane Doe; Office=Room 1004; Extension=(234)555-8914; HomePhone=(234)555-0044; Email=jdoe@rosettacode.org} /home/jdoe /bin/bash
Export records to file.
if (-not(Test-FileLock -Path ".\passwd.txt"))
{
$records | Export-File -Path ".\passwd.txt"
}
This is the file.
Get-Content -Path ".\passwd.txt"
- Output:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash
Add a record to the record set.
$records+= New-Record -Account 'xyz' `
-Password 'x' `
-UID 1003 `
-GID 1000 `
-FullName 'X Yz' `
-Office 'Room 1003' `
-Extension '(234)555-8913' `
-HomePhone '(234)555-0033' `
-Email 'xyz@rosettacode.org' `
-Directory '/home/xyz' `
-Shell '/bin/bash'
Display record objects, sorted on last name; and display them.
$records | Sort-Object { $_.GECOS.FullName.Split(" ")[1] } | Format-Table -AutoSize
- Output:
Account Password UID GID GECOS Directory Shell
------- -------- --- --- ----- --------- -----
jdoe x 1002 1000 @{FullName=Jane Doe; Office=Room 1004; Extension=(234)555-8914; HomePhone=(234)555-0044; Email=jdoe@rosettacode.org} /home/jdoe /bin/bash
jsmith x 1001 1000 @{FullName=Joe Smith; Office=Room 1007; Extension=(234)555-8917; HomePhone=(234)555-0077; Email=jsmith@rosettacode.org} /home/jsmith /bin/bash
xyz x 1003 1000 @{FullName=X Yz; Office=Room 1003; Extension=(234)555-8913; HomePhone=(234)555-0033; Email=xyz@rosettacode.org} /home/xyz /bin/bash
Export records to file.
if (-not(Test-FileLock -Path ".\passwd.txt"))
{
$records | Export-File -Path ".\passwd.txt"
}
This is the file.
Get-Content -Path ".\passwd.txt"
- Output:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| PSCustomObject | (CSV?) text file | Built-in (.NET) | ☑ | ☑ | ☑ (High probability) |
Python
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| dict | CSV text file | builtin | ☑ | ☑ | ☒ |
| instance | CSV text file | builtin | To do. | ||
From a "dict" to a CSV File
#############################
# Create a passwd text file
#############################
# note that UID & gid are of type "text"
passwd_list=[
dict(account='jsmith', password='x', UID=1001, GID=1000, # UID and GID are type int
GECOS=dict(fullname='Joe Smith', office='Room 1007', extension='(234)555-8917',
homephone='(234)555-0077', email='jsmith@rosettacode.org'),
directory='/home/jsmith', shell='/bin/bash'),
dict(account='jdoe', password='x', UID=1002, GID=1000,
GECOS=dict(fullname='Jane Doe', office='Room 1004', extension='(234)555-8914',
homephone='(234)555-0044', email='jdoe@rosettacode.org'),
directory='/home/jdoe', shell='/bin/bash')
]
passwd_fields="account password UID GID GECOS directory shell".split()
GECOS_fields="fullname office extension homephone email".split()
def passwd_text_repr(passwd_rec):
# convert individual fields to string type
passwd_rec["GECOS"]=",".join([ passwd_rec["GECOS"][field] for field in GECOS_fields])
for field in passwd_rec: # convert "int" fields
if not isinstance(passwd_rec[field], str):
passwd_rec[field]=`passwd_rec[field]`
return ":".join([ passwd_rec[field] for field in passwd_fields ])
passwd_text=open("passwd.txt","w")
for passwd_rec in passwd_list:
print >> passwd_text,passwd_text_repr(passwd_rec)
passwd_text.close()
#################################
# Load text ready for appending
#################################
passwd_text=open("passwd.txt","a+")
new_rec=dict(account='xyz', password='x', UID=1003, GID=1000,
GECOS=dict(fullname='X Yz', office='Room 1003', extension='(234)555-8913',
homephone='(234)555-0033', email='xyz@rosettacode.org'),
directory='/home/xyz', shell='/bin/bash')
print >> passwd_text, passwd_text_repr(new_rec)
passwd_text.close()
##############################################
# Finally reopen and check record was appended
##############################################
passwd_list=list(open("passwd.txt","r"))
if "xyz" in passwd_list[-1]:
print "Appended record:",passwd_list[-1][:-1]
- Output:
Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Racket
The simplest format for such data in plain text is S-expression.
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| S-exprs | text file | builtin | ☑ | ☑ | ☑ |
#lang racket
(define sample1
'("jsmith" "x" 1001 1000
("Joe Smith" "Room 1007" "(234)555-8917" "(234)555-0077" "jsmith@rosettacode.org")
"/home/jsmith" "/bin/bash"))
(define sample2
'("jdoe" "x" 1002 1000
("Jane Doe" "Room 1004" "(234)555-8914" "(234)555-0044" "jdoe@rosettacode.org")
"/home/jdoe" "/bin/bash"))
(define sample3
'("xyz" "x" 1003 1000
("X Yz" "Room 1003" "(234)555-8913" "(234)555-0033" "xyz@rosettacode.org")
"/home/xyz" "/bin/bash"))
(define passwd-file "sexpr-passwd")
(define (write-passwds mode . ps)
(with-output-to-file passwd-file #:exists mode
(λ() (for ([p (in-list ps)]) (printf "~s\n" p)))))
(define (lookup username)
(with-input-from-file passwd-file
(λ() (for/first ([p (in-producer read eof)]
#:when (equal? username (car p)))
p))))
(printf "Creating file with two sample records.\n")
(write-passwds 'replace sample1 sample2)
(printf "Appending third sample.\n")
(write-passwds 'append sample3)
(printf "Looking up xyz in current file:\n=> ~s\n" (lookup "xyz"))
- Output:
Creating file with two sample records.
Appending third sample.
Looking up xyz in current file:
=> ("xyz" "x" 1003 1000 ("X Yz" "Room 1003" "(234)555-8913" "(234)555-0033" "xyz@rosettacode.org") "/home/xyz" "/bin/bash")
Raku
(formerly Perl 6)
This is kind of silly as it takes a string, converts it to a record, and then instantly converts it back to a string to write out to a file. Most of the "record handling" code is just demonstrating a possible way to store records in memory. It really has nothing to do with appending a string to a file.
class record {
has $.name;
has $.password;
has $.UID;
has $.GID;
has $.fullname;
has $.office;
has $.extension;
has $.homephone;
has $.email;
has $.directory;
has $.shell;
method gecos { join ',', $.fullname, $.office, $.extension, $.homephone, $.email }
method gist {
join ':',
$.name,
$.password,
$.UID,
$.GID,
self.gecos,
$.directory,
$.shell;
}
};
my $fname = 'foo.fil';
given $fname.IO.open(:w) { .close }; # clear file
sub append ($file, $line){
my $fh = $file.IO.open(:a) or fail "Unable to open $file";
given $fh {
# Get a lock on the file, waits until lock is active
.lock;
# seek to the end in case some other process wrote to
# the file while we were waiting for the lock
.seek(0, SeekType::SeekFromEnd);
# write the record
.say: $line;
.close;
}
}
sub str-to-record ($str) {
my %rec = <name password UID GID fullname office extension
homephone email directory shell> Z=> $str.split(/<[:,]>/);
my $user = record.new(|%rec);
}
for
'jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash',
'jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash'
-> $line {
my $thisuser = str-to-record $line;
$fname.&append: $thisuser.gist;
}
put "Last line of $fname before append:";
put $fname.IO.lines.tail;
$fname.&append: str-to-record('xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash').gist;
put "Last line of $fname after append:";
put $fname.IO.lines.tail;
- Output:
Last line of foo.fil before append: jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash Last line of foo.fil after append: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Class | Text file | Whichever is provided by the underlying VM |
☑ | ☑ | ☑ Advisory lock Depends on OS and VM |
Note that advisory locks do not prevent some other program (if it doesn't use flock) from unexpectedly writing to the file.
RapidQ
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| QObject | CSV text file | Standard lib | ☑ | ☑ | ☑ |
The easy short solution
'Short solution: Append record and read last record
$Include "Rapidq.inc"
dim file as qfilestream
dim filename as string
dim LogRec as string
'First create our logfile
filename = "C:\Logfile2.txt"
file.open(filename, fmCreate)
file.writeline "jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash"
file.writeline "jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jsmith:/bin/bash"
file.close
'Append record
file.open(filename, fmOpenWrite)
file.position = File.size
file.writeline "xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash"
file.close
'Read last record
file.open (filename, fmOpenRead)
while not file.EOF
LogRec = File.Readline
wend
file.close
showmessage "Appended record: " + LogRec
- Output:
Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Full solution: create an object to handle all functions
'Full solution: Create an object with all required fields and
'build-in functions to append a record and to read the last record
$include "Rapidq.inc"
Type TLogFile extends QObject
Private:
file as qfilestream
Public:
account as string
password as string
UID as integer
GID as integer
GECOS.fullname as string
GECOS.office as string
GECOS.extension as string
GECOS.homephone as string
GECOS.email as string
directory as string
shell as string
RSep as string
GSep as string
function AppendRecord(LogFile as string) as integer
with This
if fileexists(LogFile) then
Result = .file.open(LogFile, fmOpenWrite)
else
Result = .file.open(LogFile, fmCreate)
end if
.file.position = .file.size
.file.writeline .account + .RSep + .password + .RSep + str$(.UID) + .RSep + str$(.GID) + .RSep +_
.GECOS.fullname + .GSep + .GECOS.office + .GSep + .GECOS.extension +_
.GSep + .GECOS.homephone + .GSep + .GECOS.email + .RSep +_
.directory + .RSep + .shell
.file.close
end with
end function
Function ReadLastRecord(LogFile as string) as string
dim x as integer
dim LogRec as string
dim GECOSRec as string
With This
if fileexists(LogFile) then
.file.open(LogFile, fmOpenRead)
While not .file.eof
LogRec = .file.readline
Wend
.file.close
.account = field$(LogRec, .RSep, 1)
.password = field$(LogRec, .RSep, 2)
.UID = val(field$(LogRec, .RSep, 3))
.GID = val(field$(LogRec, .RSep, 4))
GECOSRec = field$(LogRec, .RSep, 5)
.directory = field$(LogRec, .RSep, 6)
.shell = field$(LogRec, .RSep, 7)
.GECOS.fullname = field$(GECOSRec, .GSep, 1)
.GECOS.office = field$(GECOSRec, .GSep, 2)
.GECOS.extension = field$(GECOSRec, .GSep, 3)
.GECOS.homephone = field$(GECOSRec, .GSep, 4)
.GECOS.email = field$(GECOSRec, .GSep, 5)
else
showmessage "Can't read file " + Logfile
end if
end with
End function
Constructor
RSep = ":"
GSep = ","
End Constructor
end type
'--- Now we can use our LogFile object:
dim LogFile as TLogFile
'--- Let's save a record: Set field values
Logfile.account = "jsmith"
Logfile.password = "X"
Logfile.UID = 1001
Logfile.GID = 1000
Logfile.directory = "/home/jsmith"
Logfile.shell = "/bin/bash"
Logfile.GECOS.fullname = "Joe Smith"
Logfile.GECOS.office = "Room 1007"
Logfile.GECOS.extension = "(234)555-8917"
Logfile.GECOS.homephone = "(234)555-0077"
Logfile.GECOS.email = "jsmith@rosettacode.org"
'--- And save it to our logfile
Logfile.appendrecord("c:\A test.txt")
'--- Let's save the second one: Set field values
Logfile.account = "jdoe"
Logfile.password = "X"
Logfile.UID = 1002
Logfile.GID = 1000
Logfile.directory = "/home/jsmith"
Logfile.shell = "/bin/bash"
Logfile.GECOS.fullname = "Jane Doe"
Logfile.GECOS.office = "Room 1004"
Logfile.GECOS.extension = "(234)555-8914"
Logfile.GECOS.homephone = "(234)555-0044"
Logfile.GECOS.email = "jdoe@rosettacode.org"
'--- And save it to our logfile
Logfile.appendrecord("c:\A test.txt")
'--- And append the last one: Set field values
Logfile.account = "xyz"
Logfile.password = "X"
Logfile.UID = 1003
Logfile.GID = 1000
Logfile.directory = "/home/xyz"
Logfile.shell = "/bin/bash"
Logfile.GECOS.fullname = "X Yz"
Logfile.GECOS.office = "Room 1003"
Logfile.GECOS.extension = "(234)555-8913"
Logfile.GECOS.homephone = "(234)555-0033"
Logfile.GECOS.email = "xyz@rosettacode.org"
'--- And save it to our logfile
Logfile.appendrecord("c:\A test.txt")
'--- Read last record: load all CSV fields in our LogFile object props
Logfile.ReadLastRecord("c:\A test.txt")
'--- And simply Read values from the objects properties
Print Logfile.account
Print Logfile.password
Print Logfile.UID
Print Logfile.GID
Print Logfile.directory
Print Logfile.shell
Print Logfile.GECOS.fullname
Print Logfile.GECOS.office
Print Logfile.GECOS.extension
Print Logfile.GECOS.homephone
Print Logfile.GECOS.email
Print ""
input "Press enter to exit:";a$
REXX
| data representation | I/O library |
append |
automatic append |
multi-tasking safe | |
|---|---|---|---|---|---|
| in memory | on disk | ||||
| strings | text file | builtin | yes | yes | yes |
The data fields for the three records were coded on two statements instead of
continuing them on separate statements for brevity.
/*REXX program writes (appends) two records, closes the file, appends another record.*/
tFID= 'PASSWD.TXT' /*define the name of the output file.*/
call lineout tFID /*close the output file, just in case,*/
/* it could be open from calling pgm.*/
call writeRec tFID,, /*append the 1st record to the file. */
'jsmith',"x", 1001, 1000, 'Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org', "/home/jsmith", '/bin/bash'
call writeRec tFID,, /*append the 2nd record to the file. */
'jdoe', "x", 1002, 1000, 'Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org', "/home/jsmith", '/bin/bash'
call lineout fid /*close the outfile (just to be tidy).*/
call writeRec tFID,, /*append the 3rd record to the file. */
'xyz', "x", 1003, 1000, 'X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org', "/home/xyz", '/bin/bash'
/*─account─pw────uid───gid──────────────fullname,office,extension,homephone,Email────────────────────────directory───────shell──*/
call lineout fid /*"be safe" programming: close the file*/
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
s: if arg(1)==1 then return arg(3); return word(arg(2) 's', 1) /*pluralizer*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
writeRec: parse arg fid,_ /*get the fileID, and also the 1st arg.*/
sep=':' /*field delimiter used in file, it ··· */
/* ··· can be unique and any size.*/
do i=3 to arg() /*get each argument and append it to */
_=_ || sep || arg(i) /* the previous arg, with a : sep.*/
end /*i*/
do tries=0 for 11 /*keep trying for 66 seconds. */
r=lineout(fid, _) /*write (append) the new record. */
if r==0 then return /*Zero? Then record was written. */
call sleep tries /*Error? So try again after a delay. */
end /*tries*/ /*Note: not all REXXes have SLEEP. */
say '***error***'; say r 'record's(r) "not written to file" fid; exit 13
/*some error causes: no write access, disk is full, file lockout, no authority*/
PASSWD.TXT file before the REXX program ran:
:::::::::::::::::::::::::::::::::::::::: Hopefully, this will be considered a comment.
PASSWD.TXT file after the REXX program ran:
:::::::::::::::::::::::::::::::::::::::: Hopefully, this will be considered a comment. jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jsmith:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Ruby
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| objects (subclass of Struct builtin) | text file | builtin | ☑ | ☑ | ☒ |
Gecos = Struct.new :fullname, :office, :extension, :homephone, :email
class Gecos
def to_s
"%s,%s,%s,%s,%s" % to_a
end
end
# Another way define 'to_s' method
Passwd = Struct.new(:account, :password, :uid, :gid, :gecos, :directory, :shell) do
def to_s
to_a.join(':')
end
end
jsmith = Passwd.new('jsmith','x',1001, 1000, Gecos.new('Joe Smith', 'Room 1007', '(234)555-8917', '(234)555-0077', 'jsmith@rosettacode.org'), '/home/jsmith', '/bin/bash')
jdoe = Passwd.new('jdoe','x',1002, 1000, Gecos.new('Jane Doe', 'Room 1004', '(234)555-8914', '(234)555-0044', 'jdoe@rosettacode.org'), '/home/jdoe', '/bin/bash')
xyz = Passwd.new('xyz','x',1003, 1000, Gecos.new('X Yz', 'Room 1003', '(234)555-8913', '(234)555-0033', 'xyz@rosettacode.org'), '/home/xyz', '/bin/bash')
filename = 'append.records.test'
# create the passwd file with two records
File.open(filename, 'w') do |io|
io.puts jsmith
io.puts jdoe
end
puts "before appending:"
puts File.readlines(filename)
# append the third record
File.open(filename, 'a') do |io|
io.puts xyz
end
puts "after appending:"
puts File.readlines(filename)
- Output:
before appending: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash after appending: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Rust
use std::fs::File;
use std::fs::OpenOptions;
use std::io::BufRead;
use std::io::BufReader;
use std::io::BufWriter;
use std::io::Result;
use std::io::Write;
use std::path::Path;
/// Password record with all fields
#[derive(Eq, PartialEq, Debug)]
pub struct PasswordRecord {
pub account: String,
pub password: String,
pub uid: u64,
pub gid: u64,
pub gecos: Vec<String>,
pub directory: String,
pub shell: String,
}
impl PasswordRecord {
/// new instance, cloning all fields
pub fn new(
account: &str,
password: &str,
uid: u64,
gid: u64,
gecos: Vec<&str>,
directory: &str,
shell: &str,
) -> PasswordRecord {
PasswordRecord {
account: account.to_string(),
password: password.to_string(),
uid,
gid,
gecos: gecos.iter().map(|s| s.to_string()).collect(),
directory: directory.to_string(),
shell: shell.to_string(),
}
}
/// convert to one line string
pub fn to_line(&self) -> String {
let gecos = self.gecos.join(",");
format!(
"{}:{}:{}:{}:{}:{}:{}",
self.account, self.password, self.uid, self.gid, gecos, self.directory, self.shell
)
}
/// read record from line
pub fn from_line(line: &str) -> PasswordRecord {
let sp: Vec<&str> = line.split(":").collect();
if sp.len() < 7 {
panic!("Less than 7 fields found");
} else {
let uid = sp[2].parse().expect("Cannot parse uid");
let gid = sp[3].parse().expect("Cannot parse gid");
let gecos = sp[4].split(",").collect();
PasswordRecord::new(sp[0], sp[1], uid, gid, gecos, sp[5], sp[6])
}
}
}
/// read all records from file
pub fn read_password_file(file_name: &str) -> Result<Vec<PasswordRecord>> {
let p = Path::new(file_name);
if !p.exists() {
Ok(vec![])
} else {
let f = OpenOptions::new().read(true).open(p)?;
Ok(BufReader::new(&f)
.lines()
.map(|l| PasswordRecord::from_line(&l.unwrap()))
.collect())
}
}
/// overwrite file with records
pub fn overwrite_password_file(file_name: &str, recs: &Vec<PasswordRecord>) -> Result<()> {
let f = OpenOptions::new()
.create(true)
.write(true)
.open(file_name)?;
write_records(f, recs)
}
/// append records to file
pub fn append_password_file(file_name: &str, recs: &Vec<PasswordRecord>) -> Result<()> {
let f = OpenOptions::new()
.create(true)
.append(true)
.open(file_name)?;
write_records(f, recs)
}
/// internal, write records line by line
fn write_records(f: File, recs: &Vec<PasswordRecord>) -> Result<()> {
let mut writer = BufWriter::new(f);
for rec in recs {
write!(writer, "{}\n", rec.to_line())?;
}
Ok(())
}
fn main(){
let recs1 = vec![
PasswordRecord::new(
"jsmith",
"x",
1001,
1000,
vec![
"Joe Smith",
"Room 1007",
"(234)555-8917",
"(234)555-0077",
"jsmith@rosettacode.org",
],
"/home/jsmith",
"/bin/bash",
),
PasswordRecord::new(
"jdoe",
"x",
1002,
1000,
vec![
"Jane Doe",
"Room 1004",
"(234)555-8914",
"(234)555-0044",
"jdoe@rosettacode.org",
],
"/home/jdoe",
"/bin/bash",
),
];
overwrite_password_file("passwd", &recs1).expect("cannot write file");
let recs2 = read_password_file("passwd").expect("cannot read file");
println!("Original file:");
for r in recs2 {
println!("{}",r.to_line());
}
let append0 = vec![PasswordRecord::new(
"xyz",
"x",
1003,
1000,
vec![
"X Yz",
"Room 1003",
"(234)555-8913",
"(234)555-0033",
"xyz@rosettacode.org",
],
"/home/xyz",
"/bin/bash",
)];
append_password_file("passwd", &append0).expect("cannot append to file");
let recs2 = read_password_file("passwd").expect("cannot read file");
println!("");
println!("Appended file:");
for r in recs2 {
println!("{}",r.to_line());
}
}
- Output:
Original file: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash Appended file: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Scala
import java.io.{File, FileWriter, IOException}
import scala.io.Source
object RecordAppender extends App {
val rawDataIt = Source.fromString(rawData).getLines()
def writeStringToFile(file: File, data: String, appending: Boolean = false) =
using(new FileWriter(file, appending))(_.write(data))
def using[A <: {def close() : Unit}, B](resource: A)(f: A => B): B =
try f(resource) finally resource.close()
def rawData =
"""jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash
|jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash
|xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash""".stripMargin
case class Record(account: String,
password: String,
uid: Int,
gid: Int,
gecos: Array[String],
directory: String,
shell: String) {
def asLine: String = s"$account:$password:$uid:$gid:${gecos.mkString(",")}:$directory:$shell\n"
}
object Record {
def apply(line: String): Record = {
val token = line.trim.split(":")
require((token != null) || (token.length == 7))
this(token(0).trim,
token(1).trim,
Integer.parseInt(token(2).trim),
Integer.parseInt(token(3).trim),
token(4).split(","),
token(5).trim,
token(6).trim)
}
}
try {
val file = File.createTempFile("_rosetta", ".passwd")
using(new FileWriter(file))(writer => rawDataIt.take(2).foreach(line => writer.write(Record(line).asLine)))
writeStringToFile(file, Record(rawDataIt.next()).asLine, appending = true) // Append a record
Source.fromFile(file).getLines().foreach(line => {
if (line startsWith """xyz""") print(s"Selected record: ${Record(line).asLine}")
})
scala.compat.Platform.collectGarbage() // JVM Windows related bug workaround JDK-4715154
file.deleteOnExit()
} catch {
case e: IOException => println(s"Running Example failed: ${e.getMessage}")
}
} // 57 lines
Scheme
; Join list of strings into single string, with given separator between elements.
(define string-join
(lambda (str-lst sep)
(fold-right (lambda (ele acc) (if (string=? acc "") ele (string-append ele sep acc)))
""
str-lst)))
; Define the output file name and the three records to write to it.
(let ((filename
"mimic-passwd.txt")
(record1
(string-join
(list
"jsmith" "x" "1001" "1000"
(string-join
'("Joe Smith" "Room 1007" "(234)555-8917" "(234)555-0077" "jsmith@rosettacode.org")
",")
"/home/jsmith" "/bin/bash")
":"))
(record2
(string-join
(list
"jdoe" "x" "1002" "1000"
(string-join
'("Jane Doe" "Room 1004" "(234)555-8914" "(234)555-0044" "jdoe@rosettacode.org")
",")
"/home/jdoe" "/bin/bash")
":"))
(record3
(string-join
(list
"xyz" "x" "1003" "1000"
(string-join
'("X Yz" "Room 1003" "(234)555-8913" "(234)555-0033" "xyz@rosettacode.org")
",")
"/home/xyz" "/bin/bash")
":")))
; Write the first two records to the output file.
; Replace any existing file. Lock file for exclusive access.
(let ((op (open-file-output-port filename
(file-options replace exclusive)
'line
(make-transcoder (latin-1-codec) 'lf))))
(format op "~a~%" record1)
(format op "~a~%" record2)
(close-output-port op))
; Append the third record to the output file.
; Open existing file keeping contents. Append to file. Lock file for exclusive access.
(let ((op (open-file-output-port filename
(file-options no-fail no-truncate append exclusive)
'line
(make-transcoder (latin-1-codec) 'lf))))
(format op "~a~%" record3)
(close-output-port op)))
- Output:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| lists | text file | built-in | ☑ | ☑ | ☑ (system dependent) |
Sidef
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Hash table | Text file | built-in | ☑ | ☑ | Advisory lock |
define (
RECORD_FIELDS = %w(account password UID GID GECOS directory shell),
GECOS_FIELDS = %w(fullname office extension homephone email),
RECORD_SEP = ':',
GECOS_SEP = ',',
PASSWD_FILE = 'passwd.txt',
)
# here's our three records
var records_to_write = [
Hash(
account => 'jsmith',
password => 'x',
UID => 1001,
GID => 1000,
GECOS => Hash(
fullname => 'John Smith',
office => 'Room 1007',
extension => '(234)555-8917',
homephone => '(234)555-0077',
email => 'jsmith@rosettacode.org',
),
directory => '/home/jsmith',
shell => '/bin/bash',
),
Hash(
account => 'jdoe',
password => 'x',
UID => 1002,
GID => 1000,
GECOS => Hash(
fullname => 'Jane Doe',
office => 'Room 1004',
extension => '(234)555-8914',
homephone => '(234)555-0044',
email => 'jdoe@rosettacode.org',
),
directory => '/home/jdoe',
shell => '/bin/bash',
),
];
var record_to_append = Hash(
account => 'xyz',
password => 'x',
UID => 1003,
GID => 1000,
GECOS => Hash(
fullname => 'X Yz',
office => 'Room 1003',
extension => '(234)555-8913',
homephone => '(234)555-0033',
email => 'xyz@rosettacode.org',
),
directory => '/home/xyz',
shell => '/bin/bash',
);
func record_to_string(rec, sep = RECORD_SEP, fields = RECORD_FIELDS) {
gather {
fields.each { |field|
var r = rec{field} \\ die "Field #{field} not found"
take(field == 'GECOS' ? record_to_string(r, GECOS_SEP, GECOS_FIELDS)
: r)
}
}.join(sep)
}
func write_records_to_file(records, filename = PASSWD_FILE, append = false) {
File(filename).(append ? :open_a : :open_w)(\var fh, \var err)
err && die "Can't open #{filename}: #{err}";
fh.flock(File.LOCK_EX) || die "Can't lock #{filename}: $!"
fh.seek(0, File.SEEK_END) || die "Can't seek #{filename}: $!"
records.each { |record| fh.say(record_to_string(record)) }
fh.flock(File.LOCK_UN) || die "Can't unlock #{filename}: $!"
fh.close
}
# write two records to file
write_records_to_file(records: records_to_write);
# append one more record to file
write_records_to_file(records: [record_to_append], append: true);
# test
File(PASSWD_FILE).open_r(\var fh, \var err)
err && die "Can't open file #{PASSWD_FILE}: #{err}"
var lines = fh.lines
# There should be more than one line
assert(lines.len > 1)
# Check the last line
assert_eq(lines[-1], 'xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,' +
'(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash')
say "** Test passed!"
Note that flock uses advisory lock; some other program (if it doesn't use flock) can still unexpectedly write to the file.
Swift
import Foundation
func appendPasswd(
account: String,
passwd: String,
uid: Int,
gid: Int,
bio: String,
home: String,
shell: String
) {
let str = [
account,
passwd,
String(uid),
String(gid),
bio,
home,
shell
].joined(separator: ":").appending("\n")
guard let data = str.data(using: .utf8) else { return }
let url = URL(fileURLWithPath: "./passwd")
do {
if let fileHandle = try? FileHandle(forWritingTo: url) {
fileHandle.seekToEndOfFile()
fileHandle.write(data)
try? fileHandle.close()
} else {
try data.write(to: url)
}
} catch {
print(error)
}
}
Usage:
appendPasswd(
account: "jsmith",
passwd:"x",
uid: 1001,
gid: 1000,
bio: "Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org",
home: "/home/jsmith",
shell: "/bin/bash"
)
Tcl
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| nested lists | Colon/Comma-separated text file | builtin | ☑ | ☑ | ☑ |
Note that appending is only safe on POSIX OSes where the data is written in “small enough” amounts to a local disk. This is a limitation of the OS APIs.
# Model the data as nested lists, as that is a natural fit for Tcl
set basicRecords {
{
jsmith
x
1001
1000
{
{Joe Smith}
{Room 1007}
(234)555-8917
(234)555-0077
jsmith@rosettacode.org
}
/home/jsmith
/bin/bash
}
{
jdoe
x
1002
1000
{
{Jane Doe}
{Room 1004}
(234)555-8914
(234)555-0044
jdoe@rosettacode.org
}
/home/jsmith
/bin/bash
}
}
set addedRecords {
{
xyz
x
1003
1000
{
{X Yz}
{Room 1003}
(234)555-8913
(234)555-0033
xyz@rosettacode.org
}
/home/xyz
/bin/bash
}
}
proc printRecords {records fd} {
fconfigure $fd -buffering none
foreach record $records {
lset record 4 [join [lindex $record 4] ","]
puts -nonewline $fd [join $record ":"]\n
}
}
proc readRecords fd {
set result {}
foreach line [split [read $fd] "\n"] {
if {$line eq ""} continue
set record [split $line ":"]
# Special handling for GECOS
lset record 4 [split [lindex $record 4] ","]
lappend result $record
}
return $result
}
# Write basic set
set f [open ./passwd w]
printRecords $basicRecords $f
close $f
# Append the extra ones
# Use {WRONLY APPEND} on Tcl 8.4
set f [open ./passwd a]
printRecords $addedRecords $f
close $f
set f [open ./passwd]
set recs [readRecords $f]
close $f
puts "last record is for [lindex $recs end 0], named [lindex $recs end 4 0]"
- Output:
last record is for xyz, named X Yz
The file will have this content:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jsmith:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
UNIX Shell
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| one-dimensional arrays (indexed or associative) | text file | builtin (shell redirections) | ☑ | ☑ | OS defined |
rec1=(
jsmith
x
1001
1000
"Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org"
/home/jsmith
/bin/bash
)
rec2=(
jdoe
x
1002
1000
"Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org"
/home/jdoe
/bin/bash
)
rec3=(
xyz
x
1003
1000
"X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org"
/home/xyz
/bin/bash
)
filename=./passwd-ish
# use parentheses to run the commands in a subshell, so the
# current shell's IFS variable is not changed
(
IFS=:
echo "${rec1[*]}"
echo "${rec2[*]}"
) > "$filename"
echo before appending:
cat "$filename"
# appending, use the ">>" redirection symbol
IFS=:
echo "${rec3[*]}" >> "$filename"
echo after appending:
cat "$filename"
- Output:
before appending: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash after appending: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Ursa
# ursa appends to files by default when the out function is used
# create new passwd in working directory
decl file f
f.create "passwd"
f.open "passwd"
out "account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell" endl f
out "jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash" endl f
out "jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash" endl f
f.close
# display the created file
f.open "passwd"
out "initial file:" endl console
while (f.hasline)
out (in string f) endl console
end while
# append the new record
out "xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash" endl f
f.close
# output the new file contents
f.open "passwd"
out endl endl "file after append:" endl console
while (f.hasline)
out (in string f) endl console
end whileVisual Basic .NET
Imports System.IO
Module Module1
Class PasswordRecord
Public account As String
Public password As String
Public fullname As String
Public office As String
Public extension As String
Public homephone As String
Public email As String
Public directory As String
Public shell As String
Public UID As Integer
Public GID As Integer
Public Sub New(account As String, password As String, UID As Integer, GID As Integer, fullname As String, office As String, extension As String, homephone As String, email As String, directory As String, shell As String)
Me.account = account
Me.password = password
Me.UID = UID
Me.GID = GID
Me.fullname = fullname
Me.office = office
Me.extension = extension
Me.homephone = homephone
Me.email = email
Me.directory = directory
Me.shell = shell
End Sub
Public Overrides Function ToString() As String
Dim gecos = String.Join(",", New String() {fullname, office, extension, homephone, email})
Return String.Join(":", New String() {account, password, UID.ToString(), GID.ToString(), gecos, directory, shell})
End Function
End Class
Sub Main()
Dim jsmith As New PasswordRecord("jsmith", "x", 1001, 1000, "Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org", "/home/jsmith", "/bin/bash")
Dim jdoe As New PasswordRecord("jdoe", "x", 1002, 1000, "Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "jdoe@rosettacode.org", "/home/jdoe", "/bin/bash")
Dim xyz As New PasswordRecord("xyz", "x", 1003, 1000, "X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "xyz@rosettacode.org", "/home/xyz", "/bin/bash")
' Write these records out in the typical system format.
File.WriteAllLines("passwd.txt", New String() {jsmith.ToString(), jdoe.ToString()})
' Append a new record to the file and close the file again.
File.AppendAllText("passwd.txt", xyz.ToString())
' Open the file and demonstrate the new record has indeed been written to the end.
Dim lines = File.ReadAllLines("passwd.txt")
Console.WriteLine("Appended record: {0}", lines(2))
End Sub
End Module
- Output:
Appended record: xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
Wren
Although Wren has basic classes to work with the file system, these are only available when creating standalone scripts using the command line interpreter (CLI) and not when Wren is being embedded. In the latter case it relies on the host application for such support.
To append a record to an existing file in a CLI script, a little digging is required as the method to do this (File.openWithFlags) is currently undocumented. However, the following works fine.
import "io" for File, FileFlags
var records = [
"jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,[email protected]:/home/jsmith:/bin/bash",
"jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/home/jdoe:/bin/bash"
]
// Write records to a new file called "passwd.csv" and close it.
var fileName = "passwd.csv"
File.create(fileName) {|file|
records.each { |r| file.writeBytes(r + "\n") }
}
// Check file has been created correctly.
var contents = File.read(fileName)
System.print("Initial records:\n")
System.print(contents)
var newRec = "xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,[email protected]:/home/xyz:/bin/bash"
// Append the new record to the file and close it.
File.openWithFlags(fileName, FileFlags.writeOnly) { |file|
file.writeBytes(newRec + "\n")
}
// Check the new record has been appended correctly.
contents = File.read(fileName)
System.print("Records after appending new one:\n")
System.print(contents)
- Output:
Initial records: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,[email protected]:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/home/jdoe:/bin/bash Records after appending new one: jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,[email protected]:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,[email protected]:/home/xyz:/bin/bash
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| Wren string / class | CSV text file | Wren io module / libuv | ☑ | ☒ | ☑ (AFAIK) |
Yabasic
a = open("passwd", "a") // Open the file for appending, i.e. what you write to the file will be appended after its initial contents.
// If the file does not exist, it will be created.
print #a "account:password:UID:GID:fullname,office,extension,homephone,email:directory:shell"
print #a "jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash"
print #a "jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash"
close #a
a = open("passwd", "a")
if not a error "Could not open 'passwd' for appending"
print #a "xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash"
close #a
if (not open(a,"passwd")) error "Could not open 'passwd' for reading"
dim nameField$(1), contentField$(1)
line input #a a$
n = token(a$, nameField$(), ":,")
for i = 1 to n
if nameField$(i) = "account" field1 = i
if nameField$(i) = "homephone" field2 = i
next
print upper$(nameField$(field1)), "\t", upper$(nameField$(field2))
print
while(not eof(#a))
line input #a a$
n = token(a$, contentField$(), ":,")
print contentField$(field1), "\t", contentField$(field2)
wend
close #azkl
| Data Representation | IO Library |
Append Possible |
Automatic Append |
Multi-tasking Safe | |
|---|---|---|---|---|---|
| In core | On disk | ||||
| classes | text file | libc | ☑ | ☑ | OS defined |
var [const]
gnames=T("fullname","office","extension","homephone","email"),
pnames=T("account","password","uid","gid","gecos","directory","shell");
class Gecos{
var fullname, office, extension, homephone, email;
fcn init(str){ gnames.zipWith(setVar,vm.arglist) }
fcn toString { gnames.apply(setVar).concat(",") }
}
class Passwd{
var account,password,uid,gid,gecos,directory,shell;
fcn init(str){ pnames.zipWith(setVar,vm.arglist) }
fcn toString { pnames.apply(setVar).concat(":") }
}The class setVar method takes one or two parameters. With two, it sets the named class variable to a value; with one, it gets the var. If there aren't enough parameters, the missing ones with be set to Void (yeah, poor error checking).
fcn strToPasswd(str){ // blow apart file line to class
p:=str.strip().split(":");
g:=Gecos(p[4].split(",").xplode());
Passwd(p[0,4].xplode(),g,p[5,*].xplode());
}The List xplode method pushes the list contents to the parameter list.
jsmith:=Passwd("jsmith","x",1001, 1000,
Gecos("Joe Smith", "Room 1007", "(234)555-8917", "(234)555-0077", "jsmith@rosettacode.org"),
"/home/jsmith", "/bin/bash");
jdoe:=strToPasswd("jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,"
"jdoe@rosettacode.org:/home/jdoe:/bin/bash");
xyz:=strToPasswd("xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,"
"xyz@rosettacode.org:/home/xyz:/bin/bash");
filename:="append.records.test";
f:=File(filename,"w"); // create file with 2 records
f.writeln(jsmith,"\n",jdoe); f.close();
f:=File(filename,"a+"); // append a third record
f.writeln(xyz); f.close();
File(filename).read().text.print(); // print file- Output:
jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8917,(234)555-0077,jsmith@rosettacode.org:/home/jsmith:/bin/bash jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,jdoe@rosettacode.org:/home/jdoe:/bin/bash xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,xyz@rosettacode.org:/home/xyz:/bin/bash
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