File IO

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Task
File IO
You are encouraged to solve this task according to the task description, using any language you may know.
File IO is part of Short Circuit's Console Program Basics selection.

In this task, the job is to create a file called "output.txt", and place in it the contents of the file "input.txt", via an intermediate variable. In other words, your program will demonstrate: (1) how to read from a file into a variable, and (2) how to write a variable's contents into a file. Oneliners that skip the intermediate variable are of secondary interest — operating systems have copy commands for that.

Contents

[edit] ACL2

:set-state-ok t
 
(defun read-channel (channel limit state)
(mv-let (ch state)
(read-char$ channel state)
(if (or (null ch)
(zp limit))
(let ((state (close-input-channel channel state)))
(mv nil state))
(mv-let (so-far state)
(read-channel channel (1- limit) state)
(mv (cons ch so-far) state)))))
 
(defun read-from-file (filename limit state)
(mv-let (channel state)
(open-input-channel filename :character state)
(mv-let (contents state)
(read-channel channel limit state)
(mv (coerce contents 'string) state))))
 
(defun write-channel (channel cs state)
(if (endp cs)
(close-output-channel channel state)
(let ((state (write-byte$ (char-code (first cs))
channel state)))
(let ((state (write-channel channel
(rest cs)
state)))
state))))
 
(defun write-to-file (filename str state)
(mv-let (channel state)
(open-output-channel filename :byte state)
(write-channel channel (coerce str 'list) state)))
 
(defun copy-file (in out state)
(mv-let (contents state)
(read-from-file in (expt 2 40) state)
(write-to-file out contents state)))

[edit] Ada

[edit] Line by line

Assuming everything is fine and no error handling is required, this solution is sufficient:

with Ada.Text_IO; use Ada.Text_IO;
 
procedure Read_And_Write_File_Line_By_Line is
Input, Output : File_Type;
begin
Open (File => Input,
Mode => In_File,
Name => "input.txt");
Create (File => Output,
Mode => Out_File,
Name => "output.txt");
loop
declare
Line : String := Get_Line (Input);
begin
-- You can process the contents of Line here.
Put_Line (Output, Line);
end;
end loop;
Close (Input);
Close (Output);
exception
when End_Error =>
if Is_Open(Input) then
Close (Input);
end if;
if Is_Open(Output) then
Close (Output);
end if;
end Read_And_Write_File_Line_By_Line;

Expanded with proper error handling and reporting it reads:

with Ada.Command_Line, Ada.Text_IO; use Ada.Command_Line, Ada.Text_IO;
 
procedure Read_And_Write_File_Line_By_Line is
Read_From : constant String := "input.txt";
Write_To  : constant String := "output.txt";
 
Input, Output : File_Type;
begin
begin
Open (File => Input,
Mode => In_File,
Name => Read_From);
exception
when others =>
Put_Line (Standard_Error,
"Can not open the file '" & Read_From & "'. Does it exist?");
Set_Exit_Status (Failure);
return;
end;
 
begin
Create (File => Output,
Mode => Out_File,
Name => Write_To);
exception
when others =>
Put_Line (Standard_Error,
"Can not create a file named '" & Write_To & "'.");
Set_Exit_Status (Failure);
return;
end;
 
loop
declare
Line : String := Get_Line (Input);
begin
-- You can process the contents of Line here.
Put_Line (Output, Line);
end;
end loop;
Close (Input);
Close (Output);
exception
when End_Error =>
if Is_Open(Input) then
Close (Input);
end if;
if Is_Open(Output) then
Close (Output);
end if;
end Read_And_Write_File_Line_By_Line;

[edit] Character by character

The following example reads and writes each file one character at a time. (You should of course add error reporting as in the example above.)

with Ada.Sequential_IO;
 
procedure Read_And_Write_File_Character_By_Character is
package Char_IO is new Ada.Sequential_IO (Character);
use Char_IO;
 
Input, Output : File_Type;
Buffer  : Character;
begin
Open (File => Input, Mode => In_File, Name => "input.txt");
Create (File => Output, Mode => Out_File, Name => "output.txt");
loop
Read (File => Input, Item => Buffer);
Write (File => Output, Item => Buffer);
end loop;
Close (Input);
Close (Output);
exception
when End_Error =>
if Is_Open(Input) then
Close (Input);
end if;
if Is_Open(Output) then
Close (Output);
end if;
end Read_And_Write_File_Character_By_Character;

[edit] Using Ada.Text_IO.Text_Streams

The following solution uses stream I/O. Any file of Ada.Text_IO can be used to obtain a corresponding stream. Reading and writing streams is more efficient than reading text files directly, because it skips formatting.

with Ada.Text_IO;               use Ada.Text_IO; 
with Ada.Text_IO.Text_Streams; use Ada.Text_IO.Text_Streams;
 
procedure Using_Text_Streams is
Input, Output : File_Type;
Buffer  : Character;
begin
Open (File => Input, Mode => In_File, Name => "input.txt");
Create (File => Output, Mode => Out_File, Name => "output.txt");
loop
Buffer := Character'Input (Stream (Input));
Character'Write (Stream (Output), Buffer);
end loop;
Close (Input);
Close (Output);
exception
when End_Error =>
if Is_Open(Input) then
Close (Input);
end if;
if Is_Open(Output) then
Close (Output);
end if;
end Using_Text_Streams;

[edit] Aime

file i, o;
text s;
 
f_open(i, "input.txt", OPEN_READONLY, 0);
f_open(o, "output.txt", OPEN_CREATE | OPEN_TRUNCATE | OPEN_WRITEONLY,
0644);
 
while (f_line(i, s) ^ -1) {
f_text(o, s);
f_byte(o, '\n');
}

[edit] ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used
Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny
Works with: ELLA ALGOL 68 version Any (with appropriate job cards) - tested with release 1.8-8d
PROC copy file v1 = (STRING in name, out name)VOID: (
# note: algol68toc-1.18 - can compile, but not run v1 #
INT errno;
FILE in file, out file;
errno := open(in file, in name, stand in channel);
errno := open(out file, out name, stand out channel);
 
BOOL in ended := FALSE;
PROC call back ended = (REF FILE f) BOOL: in ended := TRUE;
on logical file end(in file, call back ended);
 
STRING line;
WHILE
get(in file, (line, new line));
# WHILE # NOT in ended DO # break to avoid excess new line #
put(out file, (line, new line))
OD;
ended:
close(in file);
close(out file)
);
 
PROC copy file v2 = (STRING in name, out name)VOID: (
INT errno;
FILE in file, out file;
errno := open(in file, in name, stand in channel);
errno := open(out file, out name, stand out channel);
 
PROC call back ended = (REF FILE f) BOOL: GO TO done;
on logical file end(in file, call back ended);
 
STRING line;
DO
get(in file, line);
put(out file, line);
get(in file, new line);
put(out file, new line)
OD;
done:
close(in file);
close(out file)
);
 
test:(
copy file v2("input.txt","output.txt")
)

[edit] AppleScript

on copyFile from src into dst
set filedata to read file src
set outfile to open for access dst with write permission
write filedata to outfile
close access outfile
end copyFile
 
copyFile from ":input.txt" into ":output.txt"

[edit] AutoHotkey

Method 1: the input file can be processed line by line.

Loop, Read, input.txt, output.txt
FileAppend, %A_LoopReadLine%`n

Method 2: the input file can be read at once if it is less than 1 GB.

FileRead, var, input.txt
FileAppend, %var%, output.txt

Method 3: the file can be copied without IO.

FileCopy, input.txt, output.txt

Binary IO is possible with this library from Laszlo.

[edit] AWK

(This does not handle properly binary files)

BEGIN {
while ( (getline <"input.txt") > 0 ) {
print >"output.txt"
}
}

[edit] Babel

(main
{ "input.txt" >>> -- File is now on stack
foo set -- File is now in 'foo'
foo "output.txt" <<< })

The spirit of Babel is to manipulate things on the stack whenever feasible. In this example, I showed how to save it into a symbolic variable (foo) but this step would not be necessary for many simple file-processing tasks, such as splitting on newlines or spaces.

Also note that the >>> (slurp) and <<< (spit) operators only handle "small" files - the limit is configurable but the default limit is 100MB. If you want to open very large files or if you need to perform a lot of interactive file I/O, Babel provides operators that wrap the C standard library fopen()/fclose() functions.

[edit] BASIC

Works with: QuickBasic version 4.5
 OPEN "INPUT.TXT" FOR INPUT AS #1
OPEN "OUTPUT.TXT" FOR OUTPUT AS #2
DO UNTIL EOF(1)
LINE INPUT #1, DATA$
PRINT #2, DATA$
LOOP
CLOSE #1
CLOSE #2
SYSTEM

[edit] Applesoft BASIC

This is only meant to copy a sequential text file. It is very unlikely that this works copying a random access text file.

100 I$ = "INPUT.TXT"
110 O$ = "OUTPUT.TXT"
120 D$ = CHR$(4)
130 M$ = CHR$(13)
140 PRINT D$"VERIFY"I$
150 PRINT D$"OPEN"O$M$D$"CLOSE"O$M$D$"DELETE"O$
160 PRINT D$"OPEN"O$M$D$"OPEN"I$;
 
170 PRINT M$D$"READ"I$
180 ONERR GOTO 250
190 GET C$
200 POKE 216,0
210 PRINT M$D$"WRITE"O$",B"B
220 IF C$ <> M$ THEN PRINT C$;
230 B = B + 1
240 GOTO 170
 
250 POKE 216,0
260 IF PEEK(222) <> 5 THEN RESUME
270 PRINT M$D$"CLOSE"I$M$D$"CLOSE"O$
 

[edit] Batch File

copy input.txt output.txt

or

type input.txt > output.txt

or

for /f "" %L in ('more^<input.txt') do echo %L>>output.txt

There may be other techniques too.

[edit] BBC BASIC

BBC BASIC for Windows has a file copy command:

      *COPY input.txt output.txt

Alternatively the copy can be done explicitly:

      infile% = OPENIN("input.txt")
outfile% = OPENOUT("output.txt")
WHILE NOT EOF#infile%
BPUT #outfile%, BGET#infile%
ENDWHILE
CLOSE #infile%
CLOSE #outfile%

[edit] Befunge

Works with: CCBI version 2.1
0110"txt.tupni"#@i10"txt.tuptuo"#@o@

This linear program tries to open "input.txt" as text file (or aborts). It then writes the content in text mode (i.e. minus trailing spaces) to "output.txt" (or aborts).

[edit] Bracmat

put$(get$"input.txt","output.txt",NEW)

[edit] C

#include <stdio.h>
 
int main(int argc, char **argv) {
FILE *in, *out;
int c;
 
in = fopen("input.txt", "r");
if (!in) {
fprintf(stderr, "Error opening input.txt for reading.\n");
return 1;
}
 
out = fopen("output.txt", "w");
if (!out) {
fprintf(stderr, "Error opening output.txt for writing.\n");
fclose(in);
return 1;
}
 
while ((c = fgetc(in)) != EOF) {
fputc(c, out);
}
 
fclose(out);
fclose(in);
return 0;
}

A couple of remarks on the preceding example:

It uses fgetc to read one character at a time. Each character is visited, even though there's nothing to do with it. Copying bigger blocks of data is much more efficient.

The following example addresses those issues. To avoid buffered IO, it uses open(), read(), write() and close(), which are part of POSIX.

Works with: POSIX
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
 
/* we just return a yes/no status; caller can check errno */
int copy_file(const char *in, const char *out)
{
int ret = 0;
int fin, fout;
ssize_t len;
char *buf[4096]; /* buffer size, some multiple of block size preferred */
struct stat st;
 
if ((fin = open(in, O_RDONLY)) == -1) return 0;
if (fstat(fin, &st)) goto bail;
 
/* open output with same permission */
fout = open(out, O_WRONLY|O_CREAT|O_TRUNC, st.st_mode & 0777);
if (fout == -1) goto bail;
 
while ((len = read(fin, buf, 4096)) > 0)
write(fout, buf, len);
 
ret = len ? 0 : 1; /* last read should be 0 */
 
bail: if (fin != -1) close(fin);
if (fout != -1) close(fout);
return ret;
}
 
int main()
{
copy_file("infile", "outfile");
return 0;
}
If it's certain that mapping the whole input file into memory poses no problem (there can be all kinds of problems), this may be the most efficient:
int copy_file(const char *in, const char *out)
{
int ret = 0;
int fin, fout;
char *bi;
struct stat st;
 
if ((fin = open(in, O_RDONLY)) == -1) return 0;
if (fstat(fin, &st)) goto bail;
 
fout = open(out, O_WRONLY|O_CREAT|O_TRUNC, st.st_mode & 0777);
if (fout == -1) goto bail;
 
bi = mmap(0, st.st_size, PROT_READ, MAP_PRIVATE, fin, 0);
 
ret = (bi == (void*)-1)
? 0 : (write(fout, bi, st.st_size) == st.st_size);
 
bail: if (fin != -1) close(fin);
if (fout != -1) close(fout);
if (bi != (void*)-1) munmap(bi, st.st_size);
return ret;
}

[edit] C#

The long way:

using System.IO;
 
using (var reader = new StreamReader("input.txt"))
using (var writer = new StreamWriter("output.txt"))
{
var text = reader.ReadToEnd();
writer.Write(text);
}

The short way:

using System.IO;
 
var text = File.ReadAllText("input.txt");
File.WriteAllText("output.txt", text);

[edit] C++

Works with: g++ version 3.4.2
#include <iostream>
#include <fstream>
#include <string>
 
using namespace std;
 
int main() {
string line;
ifstream input ( "input.txt" );
ofstream output ("output.txt");
 
if (output.is_open()) {
if (input.is_open()){
while (getline (input,line)) {
output << line << endl;
}
input.close(); // Not necessary - will be closed when variable goes out of scope.
}
else {
cout << "input.txt cannot be opened!\n";
}
output.close(); // Not necessary - will be closed when variable goes out of scope.
}
else {
cout << "output.txt cannot be written to!\n";
}
return 0;
}

Simpler version:

#include <iostream>
#include <fstream>
#include <cstdlib>
 
int main()
{
std::ifstream input("input.txt");
if (!input.is_open())
{
std::cerr << "could not open input.txt for reading.\n";
return EXIT_FAILURE;
}
 
std::ofstream output("output.txt");
if (!output.is_open())
{
std::cerr << "could not open output.txt for writing.\n";
return EXIT_FAILURE;
}
 
output << input.rdbuf();
if (!output)
{
std::cerr << "error copying the data.\n";
return EXIT_FAILURE;
}
 
return EXIT_SUCCESS;
}

Using istream- and ostream- iterators:

# include <algorithm>
# include <fstream>
 
int main() {
std::ifstream ifile("input.txt");
std::ofstream ofile("output.txt");
std::copy(std::istreambuf_iterator<char>(ifile),
std::istreambuf_iterator<char>(),
std::ostreambuf_iterator<char>(ofile));
}

Even simpler way:

#include <fstream>
 
int main()
{
std::ifstream input("input.txt");
std::ofstream output("output.txt");
output << input.rdbuf();
}

[edit] Clean

Define a function that copies the content from one file to another.

import StdEnv
 
copyFile fromPath toPath world
# (ok, fromFile, world) = fopen fromPath FReadData world
| not ok = abort ("Cannot open " +++ fromPath +++ " for reading")
# (ok, toFile, world) = fopen toPath FWriteData world
| not ok = abort ("Cannot open " +++ toPath +++ " for writing")
# (fromFile, toFile) = copyData 1024 fromFile toFile
# (ok, world) = fclose fromFile world
| not ok = abort ("Cannot close " +++ fromPath +++ " after reading")
# (ok, world) = fclose toFile world
| not ok = abort ("Cannot close " +++ toPath +++ " after writing")
= world
where
copyData bufferSize fromFile toFile
# (buffer, fromFile) = freads fromFile bufferSize
# toFile = fwrites buffer toFile
| size buffer < bufferSize = (fromFile, toFile) // we're done
= copyData bufferSize fromFile toFile // continue recursively

Apply this function to the world to copy a file.

Start world = copyFile "input.txt" "output.txt" world

[edit] Clojure

 
(use 'clojure.java.io)
 
(copy (file "input.txt") (file "output.txt"))
 
 
;; simple file writing
(spit "filename.txt" "your content here")
 
;; simple file reading
(slurp "filename.txt")
 

[edit] COBOL

[edit] Implementation

Works with: OpenCOBOL
       IDENTIFICATION DIVISION.
PROGRAM-ID. file-io.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT in-file ASSIGN "input.txt"
ORGANIZATION LINE SEQUENTIAL.
 
SELECT OPTIONAL out-file ASSIGN "output.txt"
ORGANIZATION LINE SEQUENTIAL.
 
DATA DIVISION.
FILE SECTION.
FD in-file.
01 in-line PIC X(256).
 
FD out-file.
01 out-line PIC X(256).
 
PROCEDURE DIVISION.
DECLARATIVES.
in-file-error SECTION.
USE AFTER ERROR ON in-file.
DISPLAY "An error occurred while using input.txt."
GOBACK
.
out-file-error SECTION.
USE AFTER ERROR ON out-file.
DISPLAY "An error occurred while using output.txt."
GOBACK
.
END DECLARATIVES.
 
mainline.
OPEN INPUT in-file
OPEN OUTPUT out-file
 
PERFORM FOREVER
READ in-file
AT END
EXIT PERFORM
END-READ
WRITE out-line FROM in-line
END-PERFORM
 
CLOSE in-file, out-file
.

[edit] Built-in Subroutines

Works with: OpenCOBOL
Works with: Visual COBOL
*> Originally from ACUCOBOL-GT
CALL "C$COPY" USING "input.txt", "output.txt", 0
*> Originally from Micro Focus COBOL
CALL "CBL_COPY_FILE" USING "input.txt", "output.txt"

[edit] ColdFusion

<cfif fileExists(expandPath("input.txt"))>
<cffile action="read" file="#expandPath('input.txt')#" variable="inputContents">
<cffile action="write" file="#expandPath('output.txt')#" output="#inputContents#">
</cfif>

[edit] Common Lisp

By lines:

(with-open-file (in #p"input.txt" :direction :input)
(with-open-file (out #p"output.txt" :direction :output)
(loop for line = (read-line in nil 'foo)
until (eq line 'foo)
do (write-line line out))))

By arbitrary blocks and for possibly-binary files:

(defconstant +buffer-size+ (expt 2 16))
 
(with-open-file (in #p"input.txt" :direction :input
:element-type '(unsigned-byte 8))
(with-open-file (out #p"output.txt"
:direction :output
:element-type (stream-element-type in))
(loop with buffer = (make-array +buffer-size+
:element-type (stream-element-type in))
for size = (read-sequence buffer in)
while (plusp size)
do (write-sequence buffer out :end size))))

If you're on an odd platform which actually stores text/binary/... type information for files and your CL implementation will use this information, then in should be opened with :element-type :default.

[edit] D

Works with: D version 2
import std.file: copy;
 
void main() {
copy("input.txt", "output.txt");
}
Library: Tango
Works with: D version 1

Copy the content from one file to another (exceptions are handled by Tango):

import tango.io.device.File;
 
void main()
{
auto from = new File("input.txt");
auto to = new File("output.txt", File.WriteCreate);
to.copy(from).close;
from.close;
}

Or a shorter example without explicitly closing the output file:

import tango.io.device.File;
 
void main()
{
auto to = new File("output.txt", File.WriteCreate);
to.copy(new File("input.txt")).close;
}

[edit] Delphi

Delphi supports both typed and untyped as well as a textfile type for files. Delphi provides a default 128 byte buffer for text files. This may be enlarged via a call to SetTextBuff(Var F: Text; Var Buf [Size : integer]) procedure. All other files have no buffer at all and it is the programmers option to do buffering.

The following file I/O procedures have existed since Turbo Pascal V-3.

- Read(F,V1..Vn)
- ReadLn(F,V1..Vn)
- Write(F,V1[,V2..Vn])
- WriteLn(f,V1[,V2..Vn])
- BlockRead(F,Buff,BytesToRead[,BytesRead])
- BlockWrite(F,Buff,BytesToRead[,BytesWritten])

Files are opened using:

AssignFile(f,{fully qualified path and file name})


Assigns the file name to the file structure in preparation for opening.

Reset(f)

Opens and existing file. If it does not exist EIOError is raised.


Rewrite(f)

Creates a new file and opens it for I/O. If the files exists is is overwritten.

Delphi implemented Streams of which a variant is TFileStream and are very closely related to the Windows API for file handling.

- Text File I/O -

var
f : TextFile ;
s : string ;
begin
AssignFile(f,[fully qualified file name);
Reset(f);
writeln(f,s);
Reset(f);
ReadLn(F,S);
CloseFile(
end;


- Untyped File I/O -

This is perhaps one of the most powerful I/O functions built into Pascal. This will allow you to open and read a file of ANY type, regardless of structure, size or content. Note the usage of Reset(). This is using the optional size parameter that instructs the record size of file I/O. This could have been called with SizeOf(Buff) as the optional parameter but that would have limited flexibility. Calling it with a size of ONE byte allows you to adjust the buffer size on the fly, as conditions warrant. Also note the use of the BytesRead parameter. When included in the BlockRead() function it will return the number of bytes actually read. If this is not included, then if your directive to read n bytes is greater then the size of the file, the EOF will be encountered unexpectedly and EIOError will be raised.

var
f : File ;
buff : array[1.1024] of byte ;
BytesRead : Integer ;
begin
AssignFile(f,fully qualified file name);
Reset(f,1);
Blockread(f,Buff,SizeOf(Buff),BytesRead);
CloseFile(f);
end;

- Typed File I/O -

Typed file I/O is very useful when reading and writing structures. An Address List is quiet easy to write when using this type of I/O. The same file procedures are used with some subtle differences. Bite below in the blockread and blockwrite procedures that the bytes to read or write are 1. Also note that the reset procedure is not called with a buffer size. When performing Typed File I/O the size of the type definition is the buffer size. In the BlockRead() and BlockWrite() procedures I elected to read one record. Had I declared a very large buffer of type tAddressBook of say 500 records, I could have set bytes to read as SizeOf(Buffer) thereby reading a minimum of 500 records.

type 
 
tAddressBook = Record
FName : string[20];
LName : string[30];
Address : string[30];
City : string[30];
State : string[2];
Zip5 : string[5];
Zip4 : string[4];
Phone : string[14];
Deleted : boolean ;
end;
 
var
f : file of tAddressBook ;
v : tAddressBook ;
bytes : integer ;
begin
AssignFile(f,fully qualified file name);
Reset(f);
Blockread(f,V,1,Bytes);
Edit(v);
Seek(F,FilePos(f)-1);
BlockWrite(f,v,1,bytes);
CloseFile(f);
end;

[edit] E

Works with: E-on-Java
<file:output.txt>.setText(<file:input.txt>.getText())

(This version holds the entire contents in memory.)

[edit] Eiffel

class
APPLICATION
 
create
make
 
feature {NONE} -- Initialization
 
make
-- Run application.
do
create input_file.make_open_read ("input.txt")
create output_file.make_open_write ("output.txt")
 
from
input_file.read_character
until
input_file.exhausted
loop
output_file.put (input_file.last_character)
input_file.read_character
end
 
input_file.close
output_file.close
end
 
feature -- Access
 
input_file: PLAIN_TEXT_FILE
output_file: PLAIN_TEXT_FILE
 
end

[edit] Euphoria

[edit] Read the entire file and then write it

Works with: Euphoria version 4.0.0
include std/io.e
write_lines("output.txt", read_lines("input.txt"))

[edit] Line-by-line reading and writing

Works with: Euphoria version any
integer in,out
object line
 
in = open("input.txt","r")
out = open("output.txt","w")
 
while 1 do
line = gets(in)
if atom(line) then -- EOF reached
exit
end if
puts(out,line)
end while
 
close(out)
close(in)

[edit] Erlang

 
-module( file_io ).
 
-export( [task/0] ).
 
task() ->
{ok, Contents} = file:read_file( "input.txt" ),
ok = file:write_file( "output.txt", Contents ).
 

[edit] F#

Using an intermediate variable for the input file content is not ideomatic in functional programming. Nevertheless...

open System.IO
 
let copyFile fromTextFileName toTextFileName =
let inputContent = File.ReadAllText fromTextFileName
inputContent |> fun text -> File.WriteAllText(toTextFileName, text)
 
[<EntryPoint>]
let main argv =
copyFile "input.txt" "output.txt"
0
 

[edit] Factor

Holds entire file content in memory:

"input.txt" binary file-contents
"output.txt" binary set-file-contents

A bit longer, but only holds a small amount of data in memory. If opening the file for writing fails, we want to clean up the file that's open for reading:

[
"input.txt" binary <file-reader> &dispose
"output.txt" binary <file-writer> stream-copy
] with-destructors
 

Possibly cheating:

"input.txt" "output.txt" copy-file

[edit] Forth

Forth traditionally has not had any file handling capabilities, preferring instead to operate on a disk image block by block. Most modern Forth systems however run under an existing operating system and provide methods for disk access.

\ <to> <from> copy-file
: copy-file ( a1 n1 a2 n2 -- )
r/o open-file throw >r
w/o create-file throw r>
begin
pad maxstring 2 pick read-file throw
 ?dup while
pad swap 3 pick write-file throw
repeat
close-file throw
close-file throw ;
 
\ Invoke it like this:
s" output.txt" s" input.txt" copy-file

Note the use of "2 pick" to get the input file handle and "3 pick" to get the output file handle. Local or global variables could have been used, but in this implementation simple stack manipulation was chosen. Also, only maxstring bytes are copied at a time, and the global "pad" memory area is used to hold the data. For faster copies, allocating a larger buffer could be advantageous.

Also, abort" can be used instead of throw if desired.

[edit] Fortran

Works with: Fortran version 2003
Works with: gfortran version 4.3.2

It uses the access="stream" which is defined in Fortran 2003 standard and should allow to "copy" also binary data easily.

program FileIO
 
integer, parameter :: out = 123, in = 124
integer :: err
character(len=1) :: c
 
open(out, file="output.txt", status="new", action="write", access="stream", iostat=err)
if ( err == 0 ) then
open(in, file="input.txt", status="old", action="read", access="stream", iostat=err)
if ( err == 0 ) then
err = 0
do while ( err == 0 )
read(unit=in, iostat=err) c
if ( err == 0 ) write(out) c
end do
close(in)
end if
close(out)
end if
 
end program FileIO

[edit] Frink

 
contents = read["file:input.txt"]
w = new Writer["output.txt"]
w.print[contents]
w.close[]
 

[edit] GAP

CopyFile := function(src, dst)
local f, g, line;
f := InputTextFile(src);
g := OutputTextFile(dst, false);
while true do
line := ReadLine(f);
if line = fail then
break
else
WriteLine(g, Chomp(line));
fi;
od;
CloseStream(f);
CloseStream(g);
end;

[edit] GML

var file, str;
file = file_text_open_read("input.txt");
str = "";
while (true)
{
str += file_text_read_string(file);
if (file_text_eof(file))
{
break;
}
else
{
str += chr(vk_enter);
file_text_readln(file);
}
}
file_text_close(file);
 
file = file_text_open_write("output.txt");
file_text_write_string(file,str);
file_text_close(file);

[edit] Go

package main
 
import (
"fmt"
"io/ioutil"
)
 
func main() {
b, err := ioutil.ReadFile("input.txt")
if err != nil {
fmt.Println(err)
return
}
if err = ioutil.WriteFile("output.txt", b, 0666); err != nil {
fmt.Println(err)
}
}

Alternative solution is not a one-liner, but is one of "secondary interest" that copies data from one file to another without an intermediate variable.

package main
 
import (
"io"
"log"
"os"
)
 
func CopyFile(out, in string) (err error) {
var inf, outf *os.File
inf, err = os.Open(in)
if err != nil {
return
}
defer func() {
cErr := inf.Close()
if err == nil {
err = cErr
}
}()
outf, err = os.Create(out)
if err != nil {
return
}
_, err = io.Copy(outf, inf)
cErr := outf.Close()
if err == nil {
err = cErr
}
return
}
 
func main() {
if err := CopyFile("output.txt", "input.txt"); err != nil {
log.Fatal(err)
}
}

[edit] Groovy

Using File

new File('output.txt').write(new File('input.txt').text)

Using Ant

new AntBuilder().copy(file:'input.txt', toFile:'output.txt', overwrite:true)

Buffered

new File('output.txt').withWriter( w ->
new File('input.txt').withReader( r -> w << r }
}

[edit] GUISS

Start,My Documents,Rightclick:input.txt,Copy,Menu,Edit,Paste,
Rightclick:Copy of input.txt,Rename,Type:output.txt[enter]

[edit] Haskell

Note: this doesn't keep the file in memory. Buffering is provided by lazy evaluation.

main = readFile "input.txt" >>= writeFile "output.txt"

[edit] HicEst

Copy via system call:

CHARACTER input='input.txt ', output='output.txt ', c, buffer*4096
SYSTEM(COPY=input//output, ERror=11) ! on error branch to label 11 (not shown)

Read and write line by line

OPEN(FIle=input, OLD, ERror=21) ! on error branch to label 21 (not shown)
OPEN(FIle=output)
DO i = 1, 1E300 ! "infinite" loop, exited on end-of-file error
READ( FIle=input, ERror=22) buffer ! on error (end of file) branch to label 22
WRITE(FIle=output, ERror=23) buffer ! on error branch to label 23 (not shown)
ENDDO
22 WRITE(FIle=output, CLoSe=1)

Read and write in 1 block

OPEN(FIle=input, SEQuential, UNFormatted, OLD, LENgth=len, ERror=31) ! on error branch to label 31 (not shown)
OPEN(FIle=output, SEQuential, UNFormatted, ERror=32) ! on error branch to label 32 (not shown)
ALLOCATE(c, len)
READ(FIle=input, CLoSe=1) c
WRITE(FIle=output, CLoSe=1) c END

[edit] Icon and Unicon

Icon and Unicon I/O by default is line driven. This can be changed with options in open and by the use of reads() and writes().

procedure main()
in := open(f := "input.txt","r") | stop("Unable to open ",f)
out := open(f := "output.txt","w") | stop("Unable to open ",f)
while write(out,read(in))
end

[edit] IDL

; open two LUNs
openw,unit1,'output.txt,/get
openr,unit2,'
input.txt',/get
; how many bytes to read
fs = fstat(unit2)
; make buffer
buff = bytarr(fs.size)
; transfer content
readu,unit2,buff
writeu,unit1,buff
; that'
s all
close,/all


[edit] Io

inf := File with("input.txt") openForReading
outf := File with("output.txt") openForUpdating
 
while(l := inf readLine,
outf write(l, "\n")
)
 
inf close
outf close
 

[edit] J

 'output.txt' (1!:2~ 1!:1)&< 'input.txt'

Or using the system library files:

require 'files'
'output.txt' (fwrite~ fread) 'input.txt'

[edit] Java

Works with: GCJ version 4.1.2

Simple version; Files may be closed automatically by OS, on some systems.

import java.io.*;
 
public class FileIODemo {
public static void main(String[] args) {
try {
FileInputStream in = new FileInputStream("input.txt");
FileOutputStream out = new FileOutputStream("ouput.txt");
int c;
while ((c = in.read()) != -1) {
out.write(c);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
}
}

This version closes both files after without OS intervention

import java.io.*;
 
public class FileIODemo2 {
public static void main(String args[]) {
try {
// Probably should wrap with a BufferedInputStream
final InputStream in = new FileInputStream("input.txt");
try {
// Probably should wrap with a BufferedOutputStream
final OutputStream out = new FileOutputStream("output.txt");
try {
int c;
while ((c = in.read()) != -1) {
out.write(c);
}
}
finally {
out.close();
}
}
finally {
in.close();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
}
}
Works with: Java version 1.4

Package nio

import java.io.*;
import java.nio.channels.*;
 
public class FileIODemo3 {
public static void main(String args[]) {
try {
final FileChannel in = new FileInputStream("input.txt").getChannel();
try {
final FileChannel out = new FileOutputStream("output.txt").getChannel();
try {
out.transferFrom(in, 0, in.size());
}
finally {
out.close();
}
}
finally {
in.close();
}
}
catch (Exception e) {
System.err.println("Exception while trying to copy: "+e);
e.printStackTrace(); // stack trace of place where it happened
}
}
}

This version is more in line with the other languages' implementations: it assumes simple text files, and doesn't worry too much about errors (just throws them out to the caller, the console in this case). It's shorter and simpler and shows that simple programs can be simple to write, in Java as well.

import java.io.*;
public class Test {
public static void main (String[] args) throws IOException {
BufferedReader br = new BufferedReader(new FileReader("input.txt"));
BufferedWriter bw = new BufferedWriter(new FileWriter("output.txt"));
String line;
while ((line = br.readLine()) != null) {
bw.write(line);
bw.newLine();
}
br.close();
bw.close();
}
}
Works with: Java version 7+
import java.nio.file.*;
public class Copy{
public static void main(String[] args) throws Exception{
FileSystem fs = FileSystems.getDefault();
Path in = fs.getPath("input.txt");
Path out = fs.getPath("output.txt");
Files.copy(in, out, StandardCopyOption.REPLACE_EXISTING);
}
}

[edit] JavaScript

Works with: JScript
var fso = new ActiveXObject("Scripting.FileSystemObject");
var ForReading = 1, ForWriting = 2;
var f_in = fso.OpenTextFile('input.txt', ForReading);
var f_out = fso.OpenTextFile('output.txt', ForWriting, true);
 
// for small files:
// f_out.Write( f_in.ReadAll() );
 
while ( ! f_in.AtEndOfStream) {
// ReadLine() does not include the newline char
f_out.WriteLine( f_in.ReadLine() );
}
 
f_in.Close();
f_out.Close();


Works with: Node.js
 
var fs = require('fs');
require('util').pump(fs.createReadStream('input.txt', {flags:'r'}), fs.createWriteStream('output.txt', {flags:'w+'}));
 

[edit] Julia

Here we read the content of file1 into the variable string. Then we write the content of string to file2.

string = open(readall, "file1", "r")
open(io->write(io, string), "file2", "w")

Note however that Julia has a `cp` function to copy the content of a file to another file.

cp("file1","file2")

We can also open and close the file handles manually.

infile = open("file1", "r")
outfile = open("file2", "w")
write(outfile, readall(infile))
close(outfile)
close(infile)

Here is a one-liner that guarantee that the file handle is closed even if something goes wrong during the read/write phase.

open(IO ->write(IO, open(readall, "file1", "r")), "file2", "w")

[edit] K

`output.txt 0:0:`input.txt

[edit] LabVIEW

This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code.
LabVIEW File IO.png

[edit] Lang5

: puts(*)  . "\n" . ;
: set-file '> swap open ;
: >>contents slurp puts ;
: copy-file
swap set-file 'fdst set fdst fout >>contents fdst close ;
 
'output.txt 'input.txt copy-file

[edit] Liberty BASIC

nomainwin
 
open "input.txt" for input as #f1
qtyBytes = lof( #f1)
source$ = input$( #f1, qtyBytes)
close #f1
 
open "output.txt" for output as #f2
#f2 source$;
close #f2
 
end

[edit] Lisaac

Section Header
 
+ name := FILE_IO;
 
Section Public
 
- main <- (
+ e : ENTRY;
+ f : STD_FILE;
+ s : STRING;
 
e := FILE_SYSTEM.get "input.txt";
(e != NULL).if {
f ?= e.open_read_only;
(f != NULL).if {
s := STRING.create(f.size);
f.read s size (f.size);
f.close;
};
};
 
(s != NULL).if {
e := FILE_SYSTEM.make_file "output.txt";
(e != NULL).if {
f ?= e.open;
(f != NULL).if {
f.write s from (s.lower) size (s.count);
f.close;
};
};
};
);

[edit]

Works with: UCB Logo
to copy :from :to 
openread :from
openwrite :to
setread :from
setwrite :to
until [eof?] [print readrawline]
closeall
end
 
copy "input.txt "output.txt

[edit] Lua

 
inFile = io.open("input.txt", "r")
data = inFile:read("*all") -- may be abbreviated to "*a";
-- other options are "*line",
-- or the number of characters to read.
inFile:close()
 
outFile = io.open("output.txt", "w")
outfile:write(data)
outfile:close()
 
-- Oneliner version:
io.open("output.txt", "w"):write(io.open("input.txt", "r"):read("*a"))
 

[edit] MAXScript

inFile = openFile "input.txt"
outFile = createFile "output.txt"
while not EOF inFile do
(
format "%" (readLine inFile) to:outFile
)
close inFile
close outFile

[edit] Mathematica

SetDirectory@NotebookDirectory[];
If[FileExistsQ["output.txt"], DeleteFile["output.txt"], Print["No output yet"] ];
CopyFile["input.txt", "output.txt"]

[edit] Mercury

:- module file_io.
:- interface.
 
:- import_module io.
:- pred main(io::di, io::uo) is det.
 
:- implementation.
 
main(!IO) :-
io.open_input("input.txt", InputRes, !IO),
(
InputRes = ok(Input),
io.read_file_as_string(Input, ReadRes, !IO),
(
ReadRes = ok(Contents),
io.close_input(Input, !IO),
io.open_output("output.txt", OutputRes, !IO),
(
OutputRes = ok(Output),
io.write_string(Output, Contents, !IO),
io.close_output(Output, !IO)
 ;
OutputRes = error(OutputError),
print_io_error(OutputError, !IO)
)
 ;
ReadRes = error(_, ReadError),
print_io_error(ReadError, !IO)
)
 ;
InputRes = error(InputError),
print_io_error(InputError, !IO)
).
 
:- pred print_io_error(io.error::in, io::di, io::uo) is det.
 
print_io_error(Error, !IO) :-
io.stderr_stream(Stderr, !IO),
io.write_string(Stderr, io.error_message(Error), !IO),
io.set_exit_status(1, !IO).

[edit] mIRC Scripting Language

Works with: mIRC
alias Write2FileAndReadIt {
.write myfilename.txt Goodbye Mike!
.echo -a Myfilename.txt contains: $read(myfilename.txt,1)
}

[edit] Modula-3

MODULE FileIO EXPORTS Main;
 
IMPORT IO, Rd, Wr;
 
<*FATAL ANY*>
 
VAR
infile: Rd.T;
outfile: Wr.T;
txt: TEXT;
 
BEGIN
infile := IO.OpenRead("input.txt");
outfile := IO.OpenWrite("output.txt");
txt := Rd.GetText(infile, LAST(CARDINAL));
Wr.PutText(outfile, txt);
Rd.Close(infile);
Wr.Close(outfile);
END FileIO.

The code <*FATAL ANY*> is a pragma that tells the program to die if any exceptions (such as read/write errors) occur.

[edit] NetRexx

Works with: Java version 7

Takes advantage of some of the new path and file handling features of Java's java.nio library.

/* NetRexx */
options replace format comments java crossref symbols nobinary
 
import java.nio.
 
parse arg infileName outfileName .
 
if infileName = '' | infileName.length = 0 then infileName = 'data/input.txt'
if outfileName = '' | outfileName.length = 0 then outfileName = 'data/output.txt'
 
binaryCopy(infileName, outfileName)
 
return
 
method binaryCopy(infileName, outfileName) public static
 
do
infile = Paths.get('.', [String infileName])
outfile = Paths.get('.', [String outfileName])
fileOctets = Files.readAllBytes(infile)
Files.write(outfile, fileOctets, [StandardOpenOption.WRITE, StandardOpenOption.CREATE])
 
catch ioex = IOException
ioex.printStackTrace()
end
 
return
 

[edit] Objeck

use IO;
 
bundle Default {
class Test {
function : Main(args : String[]) ~ Nil {
len := File->Size("input.txt");
buffer := Byte->New[len];
in := FileReader->New("input.txt");
if(in->IsOpen() <> Nil) {
in->ReadBuffer(0, len, buffer);
out := FileWriter->New("output.txt");
if(out->IsOpen() <> Nil) {
out->WriteBuffer(0, len, buffer);
out->Close();
};
in->Close();
};
}
}
}

[edit] Objective-C

Works with: Cocoa
Works with: GNUstep

Read the contents of input.txt and place it in output.txt, creating a file if needed:

NSData *data = [NSData dataWithContentsOfFile:@"input.txt"];
 
[data writeToFile:@"output.txt" atomically:YES];

Displayed without error checking to make it more clear. In real code you will need to add lot of error checking code, and maybe use dataWithContentsOfFile:error: if you want to get error information on failure. However, this code will mostly work correctly even if input does not exist or is not accessible. dataWithContentsOfFile: will return nil, and sending nil the message writeTofile:atomically: does nothing :-)

The second argument (atomically:YES) write the content to a temporary file, and rename the temporary file to the destination file, replacing existing file.

[edit] Object Pascal

For procedural code see the Delphi code, which is perfectly fine in ObjectPascal.

For a more object oriented style one can use a TFilestream:

uses
classes;
begin
with TFileStream.Create('input.txt', fmOpenRead) do
try
SaveToFile('output.txt');
finally
Free;
end;
end;

[edit] OCaml

By line:

let () =
let ic = open_in "input.txt" in
let oc = open_out "output.txt" in
try
while true do
let s = input_line ic in
output_string oc s;
output_char oc '\n';
done
with End_of_file ->
close_in ic;
close_out oc;
;;

By character:

let () =
let ic = open_in "input.txt" in
let oc = open_out "output.txt" in
try
while true do
let c = input_char ic in
output_char oc c
done
with End_of_file ->
close_in ic;
close_out oc;
;;

(Notice that ic and oc, of type in_channel and out_channel, are buffered)

[edit] OpenEdge/Progress

COPY-LOB FROM FILE "input.txt" TO FILE "output.txt".

[edit] Oz

declare
class TextFile from Open.file Open.text end
 
In = {New TextFile init(name:"input.txt")}
Out = {New TextFile init(name:"output.txt" flags:[write text create truncate])}
 
proc {CopyAll In Out}
case {In getS($)} of false then skip
[] Line then
{Out putS(Line)}
{CopyAll In Out}
end
end
in
{CopyAll In Out}
{Out close}
{In close}

[edit] PARI/GP

f=read("filename.in");
write("filename.out", f);

[edit] Pascal

The | FreePascal wiki gives a detailed description. For procedureal code see the Delphi examples. The ObjectPascal example is more OO coding style.

[edit] Perl

Works with: Perl version 5.8.8
#!/usr/bin/perl
 
open my $fh_in, '<', 'input.txt' or die "could not open <input.txt> for reading: $!";
open my $fh_out, '>', 'output.txt' or die "could not open <output.txt> for writing: $!";
# '>' overwrites file, '>>' appends to file, just like in the shell
 
binmode $fh_out; # marks filehandle for binary content on systems where that matters
 
print $fh_out $_ while <$fh_in>;
# prints current line to file associated with $fh_out filehandle
 
# the same, less concise
#while (<$fh_in>) {
# print $fh_out $_;
#};
 
close $fh_in;
close $fh_out;

Perl has also a powerful mechanism in conjunction with opening files called IO disciplines. It allows you to automatically apply chainable transformations on the input and output. Mangling newlines, gzip (de)compression and character encoding are the most used examples.

[edit] Perl 6

my $in = open "input.txt";
my $out = open "output.txt", :w;
for $in.lines -> $line {
$out.say($line);
}

or, using the new slurp operator:

(open "output.txt", :w).print(slurp "input.txt")

[edit] PHP

Works with: PHP version 4
<?php
 
if (!$in = fopen('input.txt', 'r')) {
die('Could not open input file.');
}
 
if (!$out = fopen('output.txt', 'w')) {
die('Could not open output file.');
}
 
while (!feof($in)) {
$data = fread($in, 512);
fwrite($out, $data);
}
 
fclose($out);
fclose($in);
?>
Works with: PHP version 5
<?php
if ($contents = file_get_contents('input.txt')) {
if (!file_put_contents('output.txt', $contents)) {
echo('Could not write output file.');
}
} else {
echo('Could not open input file.');
}
?>

[edit] PicoLisp

[edit] Using a variable

(let V (in "input.txt" (till))
(out "output.txt" (prin V)) )

[edit] Skipping intermediate variable

(in "input.txt"
(out "output.txt"
(echo) ) )

[edit] PL/I

 
declare in file, out file;
 
open file (in) title ('/INPUT.TXT,type(text),recsize(100)') input;
open file (out) title ('/OUTPUT.TXT,type(text),recsize(100') output;
do forever;
get file (in) edit (line) (L);
put file (out) edit (line) (A);
end;
 

[edit] Pop11

Char by char copy:

lvars i_stream = discin('input.txt');
lvars o_stream = discout('output.txt');
lvars c;
while (i_stream() ->> c) /= termin do
o_stream(c);
endwhile;

Low level block copy:

lvars i_file = sysopen('input.txt', 0, true);
lvars o_file = syscreate('output.txt', 1, true);
lvars buff = inits(4096);
lvars i;
while (sysread(i_file, buff, length(buff)) ->> i) > 0 do
syswrite(o_file, buff, i);
endwhile;

[edit] PowerShell

Read the input file then pipe it's contents to output file. Assumes that the files are in the same folder that the script is executing in.

Get-Content $PWD\input.txt | Out-File $PWD\output.txt

Using an alternate cmdlet to write the file

Get-Content $PWD\input.txt | Set-Content $PWD\output.txt

[edit] PureBasic

Basic file copy

CopyFile("input.txt","output.txt")


Line by line

in = ReadFile(#PB_Any,"input.txt")
If in
out = CreateFile(#PB_Any,"output.txt")
If out
Define MyLine$
While Not Eof(in)
MyLine$ = ReadString(in)
WriteString(out,MyLine$)
Wend
CloseFile(out)
EndIf
CloseFile(in)
EndIf


Reading & writing the complete file in one pass

If ReadFile(0,"input.txt")
Define MyLine$, *Buffer, length
length=FileSize("input.txt")
*Buffer = AllocateMemory(length)
If *Buffer
If OpenFile(1,"output.txt")
ReadData(0, *Buffer, length)
WriteData(1, *Buffer, length)
CloseFile(1)
EndIf
FreeMemory(*Buffer)
EndIf
CloseFile(0)
EndIf

[edit] Python

The following use of the standard libraries shutil.copyfile is to be preferred. (Current source code ensures that failure to open files raises appropriate exceptions, a restricted buffer is used to copy the files using binary mode, and any used file descriptors are always closed).

import shutil
shutil.copyfile('input.txt', 'output.txt')

However the following example shows how one would do file I/O of other sorts:

infile = open('input.txt', 'r')
outfile = open('output.txt', 'w')
for line in infile:
outfile.write(line)
outfile.close()
infile.close()

This does no error checking. A more robust program would wrap each open with exception handling blocks:

import sys
try:
infile = open('input.txt', 'r')
except IOError:
print >> sys.stderr, "Unable to open input.txt for input"
sys.exit(1)
try:
outfile = open('output.txt', 'w')
except IOError:
print >> sys.stderr, "Unable to open output.txt for output"
sys.exit(1)
try: # for finally
try: # for I/O
for line in infile:
outfile.write(line)
except IOError, e:
print >> sys.stderr, "Some I/O Error occurred (reading from input.txt or writing to output.txt)"
finally:
infile.close()
outfile.close()

In Python 2.6 (or 2.5 if we use from __future__ import with_statement) we can more simply write:

import sys
try:
with open('input.txt') as infile:
with open('output.txt', 'w') as outfile:
for line in infile:
outfile.write(line)
except IOError:
print >> sys.stderr, "Some I/O Error occurred"
sys.exit(1)

The files will automatically be closed on exit of their with: blocks. (Thus even if an I/O error occurred while reading the middle of the input file we are assured that the .close() method will have been called on each of the two files.

[edit] R

If files are textual we can use readLines ("-1" means "read until the end")

src <- file("input.txt", "r")
dest <- file("output.txt", "w")
 
fc <- readLines(src, -1)
writeLines(fc, dest)
close(src); close(dest)

If the files are not textual but "generic":

src <- file("input.txt", "rb")
dest <- file("output.txt", "wb")
 
while( length(v <- readBin(src, "raw")) > 0 ) {
writeBin(v, dest)
}
close(src); close(dest)

Another simpler way is to use file.copy

file.copy("input.txt", "output.txt", overwrite = FALSE)

[edit] Racket

#lang racket
(define file-content
(with-input-from-file "input.txt"
(lambda ()
(let loop ((lst null))
(define new (read-char))
(if (eof-object? new)
(apply string lst)
(loop (append lst (list new))))))))
 
(with-output-to-file "output.txt"
(lambda ()
(write file-content)))

[edit] RapidQ

File I/O is one of the things where RapidQ differs from standard Basic. RapidQ uses file streams.

The first version copies text line by line, as in the BASIC example.

$INCLUDE "rapidq.inc"
 
DIM File1 AS QFileStream
DIM File2 AS QFileStream
 
File1.Open("input.txt", fmOpenRead)
File2.Open("output.txt", fmCreate)
 
WHILE NOT File1.EOF
data$ = File1.ReadLine
File2.WriteLine(data$)
WEND
 
File1.Close
File2.Close

When just copying data, the code can be simplified by using the CopyFrom method.
(The second parameter for CopyFrom is number of bytes to copy, 0 = copy the whole file.)

$INCLUDE "rapidq.inc"
 
DIM File1 AS QFileStream
DIM File2 AS QFileStream
 
File1.Open("input.txt", fmOpenRead)
File2.Open("output.txt", fmCreate)
 
File2.CopyFrom(File1, 0)
 
File1.Close
File2.Close

[edit] Raven

'input.txt' read 'output.txt' write

[edit] REALbasic

 
Sub WriteToFile(input As FolderItem, output As FolderItem)
Dim tis As TextInputStream
Dim tos As TextOutputStream
tis = tis.Open(input)
tos = tos.Create(output)
While Not tis.EOF
tos.WriteLine(tis.ReadLine)
Wend
tis.Close
tos.Close
End Sub
 

[edit] REBOL

write %output.txt read %input.txt
 
; No line translations:
write/binary %output.txt read/binary %input.txt
 
; Save a web page:
write/binary %output.html read http://rosettacode.org
 

[edit] Retro

with files'
here dup "input.txt" slurp "output.txt" spew

[edit] REXX

In rexx, filename association is used rather than numeric stream numbers and explicit file opening is not required.

[edit] version 1

/*REXX program to read a file and store the contents into an output file*/
 
ifid = 'input.txt' /*name of the input file. */
ofid = 'output.txt' /*name of the output file. */
call lineout ofid,,1 /*insure output starts at line 1.*/
 
do while lines(ifid)\==0 /*read until finished. */
y = linein(ifid) /*read a record from input. */
call lineout ofid,y /*write a record to output.nt. */
end
/*stick a fork in it, we're done.*/

[edit] version 2

/*REXX program to read a file and store the contents into an output file*/
/*(same as the 1st example, but is faster because no intermediate step.)*/
 
ifid = 'input.txt' /*name of the input file. */
ofid = 'output.txt' /*name of the output file. */
call lineout ofid,,1 /*insure output starts at line 1.*/
 
do while lines(ifid)\==0 /*read until finished. */
call lineout ofid, linein(ifid) /*read & write in one statement. */
end /*while*/
/*stick a fork in it, we're done.*/

[edit] version 3

Note that this version is limited to files less than one million bytes (and/or possibly virtual memory).

/*REXX program to read a file and write contents to an output file*****
* 03.09.2012 Walter Pachl (without erase string would be appended)
**********************************************************************/

ifid='input.txt' /*name of the input file. */
ofid='output.txt' /*name of the output file. */
'erase' ofid /* avoid appending */
s=charin(ifid,,1000000) /* read the input file */
Call charout ofid,s /* write to output file */

[edit] Ruby

In general, open both files in binary mode.

str = File.open('input.txt', 'rb') {|f| f.read}
File.open('output.txt', 'wb') {|f| f.write str}

If 'input.txt' is a text file, we may forget binary mode. If no pathname begins with a pipe '|', then we may use IO::read and Kernel#open. (The pipe is a problem, because IO.read('| uname') or open('| sh', 'w') would open a subprocess and not a file.)

# Only if 'input.txt' is a text file!
# Only if pipe '|' is not first character of path!
str = IO.read('input.txt')
open('output.txt', 'w') {|f| f.write str}

To copy a file block by block, use FileUtils from the standard library.

require 'fileutils'
FileUtils.copy_file 'input.txt', 'output.txt'

[edit] Run BASIC

open "input.txt" for input as #in
fileLen = LOF(#in) 'Length Of File
fileData$ = input$(#in, fileLen) 'read entire file
close #in
 
open "output.txt" for output as #out
print #out, fileData$ 'write entire fie
close #out
end
 
' or directly with no intermediate fileData$
 
open "input.txt" for input as #in
open "output.txt" for output as #out
fileLen = LOF(#in) 'Length Of File
print #out, input$(#in, fileLen) 'entire file
close #in
close #out
 

[edit] Rust

extern mod std;
use std::io;
 
fn main() {
let input_file = &Path("input.txt");
let input = io::read_whole_file_str(input_file);
match input {
Err(e) => fail!(e),
Ok(_) => {}
}
 
let output_file = &Path("output.txt");
let output = io::file_writer(output_file, [io::Create, io::Truncate]);
match output {
Err(e) => fail!(e),
Ok(_) => {}
}
 
output.unwrap().write_str(input.unwrap());
}

[edit] Scala

Library: Scala
import java.io.{ FileNotFoundException, PrintWriter }
 
object FileIO extends App {
try {
val MyFileTxtSource = scala.io.Source.fromFile("input.txt")
val MyFileTxtTarget = new PrintWriter("output.txt")
 
val str = MyFileTxtSource.mkString
MyFileTxtTarget.print(str)
 
MyFileTxtTarget.close()
MyFileTxtSource.close()
}
} catch {
case e: FileNotFoundException => println(e.getLocalizedMessage())
case e: Throwable => {
println("Some other exception type:")
e.printStackTrace()
}
}
}

[edit] Scheme

Character by character copy
; Open ports for the input and output files
(define in-file (open-input-file "input.txt"))
(define out-file (open-output-file "output.txt"))
 
; Read and write characters from the input file
; to the output file one by one until end of file
(do ((c (read-char in-file) (read-char in-file)))
((eof-object? c))
(write-char c out-file))
 
; Close the ports
(close-input-port in-file)
(close-output-port out-file)
 

[edit] Seed7

The library osfiles.s7i contains the function copyFile which can be used to copy a source file to a destination.

$ include "seed7_05.s7i";
include "osfiles.s7i";
 
const proc: main is func
begin
copyFile("input.txt", "output.txt");
end func;

[edit] Slate

(File newNamed: 'input.txt' &mode: File Read) sessionDo: [| :in |
(File newNamed: 'output.txt' &mode: File CreateWrite) sessionDo: [| :out |
in >> out]]

[edit] Smalltalk

| in out |
in := FileStream open: 'input.txt' mode: FileStream read.
out := FileStream open: 'output.txt' mode: FileStream write.
[ in atEnd ]
whileFalse: [
out nextPut: (in next)
]

[edit] SNOBOL4

 
input(.input,5,,'input.txt')
output(.output,6,,'output.txt')
while output = input  :s(while)
end


[edit] Standard ML

Works with: SML/NJ version 110.59
fun copyFile (from, to) =
let
val instream = TextIO.openIn from
val outstream = TextIO.openOut to
val () = TextIO.output (outstream, TextIO.inputAll instream)
val () = TextIO.closeIn instream
val () = TextIO.closeOut outstream
in
true
end handle _ => false;

[edit] Tcl

Works with: tclsh
Works with: eTcl
Works with: wish
Works with: tixwish
Works with: tclkit
set in [open "input.txt" r]
set out [open "output.txt" w]
# Obviously, arbitrary transformations could be added to the data at this point
puts -nonewline $out [read $in]
close $in
close $out

For larger files, it is better to use the fcopy command, though in general this restricts what operations can be performed rather more (only encoding and end-of-line translations are possible — or more general byte-level transformations with the generic filter mechanism provided in Tcl 8.6 — none of which are shown here):

set in [open "input.txt" r]
set out [open "output.txt" w]
fcopy $in $out
close $in
close $out

Or the minimal version if we don't need any processing of the data at all:

file copy input.txt output.txt

[edit] Other key file I/O operations

Writing a line to a file:
#open file for writing
set myfile [open "README.TXT" w]
#write something to the file
puts $myfile "This is line 1, so hello world...."
#close the file
close $myfile
Reading a line from a file:
#open file for reading
set myfile [open "README.TXT" r]
#read something from the file
gets $myfile mydata
#show what was read from the file
#should print "This is line1, so hello world...."
puts $mydata
#close the file
close $myfile

[edit] Toka

This is one method, which works with any type of file:

( source dest -- )
{
value| source dest size buffer |
{
{
[ "W" file.open to dest ] is open-dest
[ "R" file.open to source ] is open-source
[ open-dest open-source ]
} is open-files
{
[ source file.size to size ] is obtain-size
[ size malloc to buffer ] is allocate-buffer
[ obtain-size allocate-buffer ]
} is create-buffer
[ source dest and 0 <> ] is check
[ open-files create-buffer check ]
} is prepare
[ source buffer size file.read drop ] is read-source
[ dest buffer size file.write drop ] is write-dest
[ source file.close dest file.close ] is close-files
[ prepare [ read-source write-dest close-files ] ifTrue ]
} is copy-file

And a much simpler way for plain text files, making use of file.slurp:

[ ( source dest -- ) 
swap file.slurp dup 0 <>
[ >r "W" file.open dup r> string.getLength file.write drop file.close ] ifTrue
] is copy-file

And a test:

" input.txt" " output.txt" copy-file

[edit] UNIX Shell

Using the 'read' built-in

  • Hint: mksh(1) manual says, "If read is run in a loop such as while read foo; do ...; done then leading whitespace will be removed (IFS) and backslashes processed. You might want to use while IFS= read -r foo; do ...; done for pristine I/O."
  • Caveat: output.txt will end with a newline, whether or not input.txt ended with one.
#!/bin/sh
while IFS= read -r a; do
printf '%s\n' "$a"
done <input.txt >output.txt

Another way, using the 'cat' program

#!/bin/sh
cat input.txt >output.txt

Yet another way, using the 'cp' utility

#!/bin/sh
cp input.txt output.txt

[edit] Ursala

I/O in Ursala is meant to be handled transparently by the run time system. The application is passed the input files as an argument and expected to return the output files as a result.

Returning a copy of the input file with a new name causes it to be written as a new file.

#import std
 
#executable ('parameterized','')
 
fileio = ~command.files; &h.path.&h:= 'output.txt'!

[edit] VBScript

one liner (-2 for system default encoding)

CreateObject("Scripting.FileSystemObject").OpenTextFile("output.txt",2,-2).Write CreateObject("Scripting.FileSystemObject").OpenTextFile("input.txt", 1, -2).ReadAll

[edit] Vedit macro language

An edit buffer is normally used as "string variable" in Vedit. To read a file into edit buffer, simply open the file. The file contents can then be modified if required before saving into a new file.

File_Open("input.txt")
File_Save_As("output.txt", NOMSG)
Buf_Close(NOMSG)

[edit] Visual Basic .NET

Works with: Visual Basic .NET version 9.0+
'byte copy
My.Computer.FileSystem.WriteAllBytes("output.txt", _
My.Computer.FileSystem.ReadAllBytes("input.txt"), False)
 
'text copy
Using input = IO.File.OpenText("input.txt"), _
output As New IO.StreamWriter(IO.File.OpenWrite("output.txt"))
output.Write(input.ReadToEnd)
End Using
 
'Line by line text copy
Using input = IO.File.OpenText("input.txt"), _
output As New IO.StreamWriter(IO.File.OpenWrite("output.txt"))
Do Until input.EndOfStream
output.WriteLine(input.ReadLine)
Loop
End Using

[edit] Wart

with infile "input.txt"
with outfile "output.txt"
whilet line (read_line)
prn line

[edit] XPL0

Usage: fileio <input.txt >output.txt

include c:\cxpl\codes;
int I, C;
char IntermediateVariable;
[IntermediateVariable:= GetHp;
I:= 0;
repeat C:= ChIn(1);
IntermediateVariable(I):= C;
I:= I+1;
until C = $1A; \EOF
I:= 0;
repeat C:= IntermediateVariable(I);
I:= I+1;
ChOut(0, C);
until C = $1A; \EOF
]

[edit] zkl

var d=File("input.txt").read();
(f:=File("output.txt","w")).write(d); f.close();
File("output.txt").pump(Console); // verify

Need to close output.txt because it can take the garbage collector a while to notice that the file can be closed.

var in=File("input.txt"), out=File("output.txt","w");
foreach line in (in) { out.write(line) }
out.close(); // or out=Void and let GC close the file
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