Append a record to the end of a text file

From Rosetta Code
Task
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.
Source record field types and contents.
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,[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
Record to be appended.
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,[email protected] /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,[email protected]:/home/xyz:/bin/bash

Finally: Provide a summary of the language's "append record" capabilities in a table. eg.

Append Capabilities.
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.

AWK[edit]

 
# 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,[email protected]:/home/jsmith:/bin/bash") >fn
print("jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/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,[email protected]:/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,[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
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,[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
4 records

Batch File[edit]

 
@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,[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

New contents of append.txt:
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

C[edit]

Append Capabilities.
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", "[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"}
};
 
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", "[email protected]"},
"/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,[email protected]:/home/xyz:/bin/bash

C#[edit]

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", "[email protected]",
"/home/jsmith", "/bin/bash");
var jdoe = new PasswordRecord("jdoe", "x", 1002, 1000, "Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "[email protected]", "/home/jdoe",
"/bin/bash");
var xyz = new PasswordRecord("xyz", "x", 1003, 1000, "X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "[email protected]", "/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,[email protected]:/home/xyz:/bin/bash

COBOL[edit]

Works with: GnuCOBOL

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.

Append Capabilities.
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 "[email protected]" 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 "[email protected]" 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 "[email protected]" 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,[email protected]:/home/xyz:/bin/bash

Common Lisp[edit]

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" "[email protected]")
"/home/jsmith" "/bin/bash")
(list "jdoe" "x" 1002 1000
(list "Jane Doe" "Room 1004" "(234)555-8914" "(234)555-0044" "[email protected]")
"/home/jdoe" "/bin/bash")))
 
(defvar *insert*
(list "xyz" "x" 1003 1000
(list "X Yz" "Room 1003" "(234)555-8913" "(234)555-0033" "[email protected]")
"/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,[email protected]:/home/xyz:/bin/bash
Append Capabilities.
Data Representation IO
Library
Append
Possible
Automatic
Append
Multi-tasking
Safe
In core On disk
Lists Text file Common Lisp Standard Library ☑ (Hopefully!)

Elixir[edit]

Append Capabilities.
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: "[email protected]"
},
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: "[email protected]"
},
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: "[email protected]"
},
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,[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

Fortran[edit]

Prior to F90, data aggregates can't be defined so one would use an assemblage of variables with similar names rather than 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.

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 a space when what is preferable is a comma, or even a tab. But there is no standard method to specify this desire.

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. 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 to each character field. Not only would this be tedious and error-prone, there would be no 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","[email protected]"),
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","[email protected]"),
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","[email protected]"),
3 "/home/xyz","/bin/bash")
WRITE (F,*) NOTE !Append it's 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. 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   = "[email protected]                                                                  ",
 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   = "[email protected]                                                                    ",
 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   = "[email protected]                                                                     ",
 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 also applies to 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, 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[edit]

' 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", "[email protected]")
persons(2) = Person("Jane Doe", "Room 1004", "(234)555-8914", "(234)555-0044", "[email protected]" )
persons(3) = Person("X Yz", "Room 1003", "(234)555-8913", "(234)555-0033", "[email protected]" )
 
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,[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
Append Capabilities.
Data Representation IO
Library
Append
Possible
Automatic
Append
Multi-tasking
Safe
In core On disk
FB Type CSV text file FB Standard Library ☑ (Hopefully!)

Go[edit]

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", "[email protected]"},
"/home/jsmith", "/bin/bash"},
{"jdoe", "x", 1002, 1000, gecos{"Jane Doe", "Room 1004",
"(234)555-8914", "(234)555-0044", "[email protected]"},
"/home/jsmith", "/bin/bash"},
}
 
var pa = pw{"xyz", "x", 1003, 1000, gecos{"X Yz", "Room 1003",
"(234)555-8913", "(234)555-0033", "[email protected]"},
"/home/xyz", "/bin/bash"}
 
var expected = "xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913," +
"(234)555-0033,[email protected]:/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
Append Capabilities.
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:

  1. 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.
  2. 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.
  3. 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.
  4. The file position after opening a file is 0 unless os.O_APPEND is specified in the os.OpenFile function.
  5. 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[edit]

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', [email protected]']
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,[email protected]:/home/jsmith:/bin/bash
jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/home/jsmith:/bin/bash

File contents after new record added
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/jsmith:/bin/bash
xyz:x:1003:1000:X Yz,Room 1003,(234)555-8913,(234)555-0033,[email protected]:/home/xyz:/bin/bash

Haskell[edit]

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" "[email protected]")
 
t2 = Record "jdoe" "x" 1002 1000 "/home/jdoe" "/bin/bash"
(Gecos "Jane Doe" "Room 1004" "(234)555-8914" "(234)555-0044" "[email protected]")
 
t3 = Record "xyz" "x" 1003 1000 "/home/xyz" "/bin/bash"
(Gecos "X Yz" "Room 1003" "(234)555-8913" "(234)555-0033" "[email protected]")
 
main = do
let path = "test.txt"
forM [t1,t2,t3] (addRecord path)
lastLine <- fmap (last . lines) (readFile path)
putStrLn lastLine
 

Icon and Unicon[edit]

Works in both languages:

procedure main()
orig := [
"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/jsmith:/bin/bash"
]
new := [
"xyz:x:1003:1000:X:Yz,Room 1003,(234)555-8913,(234)555-0033,[email protected]:/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,[email protected]:/home/jsmith:/bin/bash
jdoe:x:1002:1000:Jane Doe,Room 1004,(234)555-8914,(234)555-0044,[email protected]:/home/jsmith:/bin/bash
xyz:x:1003:1000:X:Yz,Room 1003,(234)555-8913,(234)555-0033,[email protected]:/home/xyz:/bin/bash
->
Append Capabilities.
Data Representation IO
Library
Append
Possible
Automatic
Append
Multi-tasking
Safe
In core On disk
String String built-in ☑ (Not all, eg NFS)

J[edit]

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,[email protected]
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,[email protected]
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,[email protected]
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
Append Capabilities.
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[edit]

Template:Java

 
import static java.lang.Integer.parseInt;
import static java.nio.file.StandardOpenOption.APPEND;
import static java.util.Arrays.asList;
import static java.util.Arrays.stream;
import static java.util.Objects.requireNonNull;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;
 
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
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 + ':' + gecos.stream().collect(joining(",")) + ':' + directory + ':' + shell;
}
 
public static Record parse(String text) {
String[] tokens = text.split(":");
return new Record(
tokens[0],
tokens[1],
parseInt(tokens[2]),
parseInt(tokens[3]),
asList(tokens[4].split(",")),
tokens[5],
tokens[6]);
}
}
 
public static void main(String[] args) throws IOException {
String[] rawData = {
"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 = stream(rawData).map(Record::parse).collect(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, asList(records.get(2).toString()), 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,[email protected]:/home/xyz:/bin/bash

Mathematica / Wolfram Language[edit]

data = <|"account" -> "xyz", "password" -> "x", "UID" -> 1003, 
"GID" -> 1000, "fullname" -> "X Yz", "office" -> "Room 1003",
"extension" -> "(234)555-8913", "homephone" -> "(234)555-0033",
"email" -> "[email protected]", "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,[email protected]:/home/xyz:/bin/bash
Append Capabilities.
Data Representation IO
Library
Append
Possible
Automatic
Append
Multi-tasking
Safe
In core On disk
Association Nearly anything Standard Library

MATLAB / Octave[edit]

  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=[email protected]';
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=[email protected]';
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=[email protected]';
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,[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

Perl[edit]

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 => [email protected]',
},
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 => [email protected]',
},
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 => [email protected]',
},
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,[email protected]:/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,[email protected]:/home/xyz:/bin/bash

File contents:

jsmith:x:1001:1000:John 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
Append Capabilities.
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[edit]

Append Capabilities.
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.

constant filename = "passwd.txt"
integer fn
 
constant
rec1 = {"jsmith","x",1001,1000,{"Joe Smith","Room 1007","(234)555-8917","(234)555-0077","[email protected]"},"/home/jsmith","/bin/bash"},
rec2 = {"jdoe","x",1002,1000,{"Jane Doe","Room 1004","(234)555-8914","(234)555-0044","[email protected]"},"/home/jdoe","/bin/bash"},
rec3 = {"xyz","x",1003,1000,{"X Yz","Room 1003","(234)555-8913","(234)555-0033","[email protected]"},"/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,[email protected]:/home/jsmith:/bin/bash\n"
{"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\n"
{"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\n"
{"xyz","x",1003,1000,{"X Yz","Room 1003","(234)555-8913","(234)555-0033","[email protected]"},"/home/xyz","/bin/bash"}

PicoLisp[edit]

(setq L '((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,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[edit]

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
Append Capabilities.
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[edit]

Append Capabilities.
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[edit]

The simplest format for such data in plain text is S-expression.

Append Capabilities.
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")

RapidQ[edit]

Append Capabilities.
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[edit]

Append Capabilities
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[edit]

Append Capabilities.
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

Scala[edit]

Library: 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

Sidef[edit]

Translation of: Perl
Append Capabilities.
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.

Tcl[edit]

Append Capabilities.
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[edit]

Append Capabilities.
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[edit]

Translation of: Awk
# 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 while

zkl[edit]

Append Capabilities.
Data Representation IO
Library
Append
Possible
Automatic
Append
Multi-tasking
Safe
In core On disk
classes text file libc OS defined
Translation of: Ruby
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