Swap contents of two files

Question

This is a code-golf question. You need to take the contents of two separate files (i.txt and o.txt) and swap them. You can create a third file to help you with the process, but have your program delete it after the file contents are swapped. Renaming the files is now allowed again.

Programs must work for any file content.

Shortest code wins, all eligible submissions will be up-voted.

Rename the files. No need to "take the contents" and swap them to achieve the result. — Darren Stone, Dec 28 '13 at 19:32
@Darren Stone I think that should be illegal. Thanks for catching that before answers were submitted. — user10766, Dec 28 '13 at 19:33
Looks like a bad constraint, renaming is the best way to do this — hdante, Dec 28 '13 at 20:47
@hdante but 'renaming files' is not exchanging their contents. On a system that uses inodes the goal here would be for i.txt's inode to contain the data from o.txt's inode, and vice versa, so that if there are hardlinks to those inodes elsewhere, their contents will appear swapped as well. Renaming can't accomplish that. — AJMansfield, May 11 '14 at 3:07

Ry- · Accepted Answer · 2014-05-15 01:04:14Z

9

zsh, 20

<i*>t;<o*>i*;mv t o*

edited May 15 '14 at 1:04

answered Dec 28 '13 at 19:49

Ry-

5,2651 gold badge20 silver badges30 bronze badges

1

\$\begingroup\$ I like the one without a temporary file better, though: i=`<i.txt`;<o*>i*;<<<$i>o*. It’s too bad this has to be shorter. \$\endgroup\$ – Ry- Dec 28 '13 at 19:54
1

\$\begingroup\$ Rules changed to allow renaming files. You can update your code if you wish. \$\endgroup\$ – user10766 Dec 28 '13 at 20:56
\$\begingroup\$ You could save 3 chars by replacing <t>o*;rm t by mv t o* ! \$\endgroup\$ – F. Hauri May 11 '14 at 23:23
\$\begingroup\$ @F.Hauri: Ah, thanks! (There were rules against renaming at one point.) \$\endgroup\$ – Ry- May 11 '14 at 23:44
\$\begingroup\$ This code is not correct. It works only in the special case where i* and o* will match only i.txt and o.txt respectively, i.e. there is no other file with a name beginning with either "i" or "o". \$\endgroup\$ – Erwan Legrand May 15 '14 at 13:25

| Show 1 more comment

FlipTack · Accepted Answer · 2017-11-27 21:33:20Z

3

Python, 77

import os;t='.txt';r,i,o,x=[os.rename,'i'+t,'o'+t,'1'+t];r(i,x);r(o,i);r(x,o)

Python, 65

import os;t='.txt'
for a,b in zip('iox','xio'):os.rename(a+t,b+t)

Python, 63

import os;t='.txt'
for a,b in 'ix','oi','xo':os.rename(a+t,b+t)

PHP, 68

<?$r=rename;$t='.txt';$r("i$t","x");$r("o$t","i$t");$r("x","o$t");?>

Windows Batch File, 42

move i.txt x&move o.txt i.txt&move x o.txt

Windows Batch File (args), 30

move %1 x&move %2 %1&move x %2

edited Nov 27 '17 at 21:33

FlipTack

13.6k3 gold badges48 silver badges95 bronze badges

answered Dec 30 '13 at 12:13

AsksAnyway

2811 silver badge6 bronze badges

\$\begingroup\$ I didn't know you can use $r=rename to create aliases to functions in PHP. Thanks! \$\endgroup\$ – A.L May 11 '14 at 15:15

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F. Hauri · Accepted Answer · 2014-05-12 00:06:46Z

Two bash based ansers; 52 and 62 chars

shell: diff + patch (+ tee + sed...) 52

Maybe not the shorter, but I find this fun (and there is no use of temporary file):

diff -u [io]*|tee >(patch -r -)|sed 1s/i/o/|patch -R

Where content is swapped and files are modified in place:

Sample run

swapContent() { diff -u $1 $2|tee >(patch -r -)|sed 1s/$1/$2/|patch -R ;}

while read page file ;do man -Pcol\ -b $page >$file.txt;done <<<$'man i\nbash o'
printf "%s %8d  %s\n" $(join -j 2 <(stat -c '%s %n' [io]*) <(md5sum [io]*))
swapContent [io]*
printf "%s %8d  %s\n" $(join -j 2 <(stat -c '%s %n' [io]*) <(md5sum [io]*))

Could produce something like:

i.txt    46007  1da1f7533e0eab1e97cce97bb7ca1d3b
o.txt   321071  7dcd230890faf4ef848d4745eda14407
patching file o.txt
i.txt   321071  7dcd230890faf4ef848d4745eda14407
o.txt    46007  1da1f7533e0eab1e97cce97bb7ca1d3b

use of xargs to simplify `mv` requests

Not as funny, but nice anyway.

set -- {i,o}.txt t&&eval 'xargs -n2 mv<<<"' \${1,3,2,1,3,2} \"

Nota: As first patch output is not redirected, they become garbage on second patch command. This is the reason because only one patching file o.txt appear. — F. Hauri, May 11 '14 at 22:20

MisterBla · Accepted Answer · 2014-05-14 08:43:28Z

2

PHP, 89

I thought I'd give it a shot.

<?php $f1='f1.txt';$f2='f2.txt';$ft='ft.txt';copy($f1,$ft);copy($f2,$f1);rename($ft,$f2);

Ungolfed version:

<?php
$f1 = 'f1.txt';
$f2 = 'f2.txt';
$ft = 'ft.txt';

copy($f1, $ft);
copy($f2, $f1);
rename($ft, $f2);

Apparently I took 2 answers of here and combined them.. oh well.

answered May 14 '14 at 8:43

MisterBla

1815 bronze badges

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Aearnus · Accepted Answer · 2014-05-17 00:34:24Z

Ruby, 72 bytes

Wow! A Ruby code golf! I don't think that's ever been attempted before!

In all reality though, this required some nice Ruby shortcuts and a couple patterns which I found. It was my first golf ever and it was very fun to do. Without further ado, here's the golfed code:

3.times{|x|x*=2;t=".txt";a=([?i,?a,?o]*2);File.rename(a[x]+t,a[x+1]+t)}

And the ungolfed version

3.times do |x|
    x = x * 2
    t=".txt"
    a=([?i,?a,?o]*2)
    File.rename(a[x]+t, a[x+1]+t)}
end

The key factor in this is that the parameters passed to the File.rename are this, exactly:

File.rename "i.txt", "a.txt"
File.rename "o.txt", "i.txt"
File.rename "a.txt", "o.txt"

Hope this (doesn't) make sense!

mazzy · Accepted Answer · 2018-12-27 06:19:53Z

2

Powershell, 44 49 bytes

$t='.txt'
ren i$t a$t -fo
ren o$t i$t
ren a$t o$t

where ren is alias for Rename-Item. The script uses and delete a third file a.txt.

edited Dec 27 '18 at 6:19

answered Dec 24 '18 at 5:35

mazzy

6,0782 gold badges7 silver badges22 bronze badges

1

\$\begingroup\$ This can fail with certain encoding. Because gc default is UTF8NoBOM but sc default is ASCII. Try some UTF-8 files or binary files and you can see how it can fail. \$\endgroup\$ – AdmBorkBork Dec 26 '18 at 20:09
\$\begingroup\$ Indeed. Thanks. It need -e by -n parameters to ensure that the files unchanged. It would be nice to add a parameter -readCount 0 to performance. The script with rename is shorter :) Fixed. \$\endgroup\$ – mazzy Dec 27 '18 at 6:26

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Community · Accepted Answer · 2020-06-17 09:04:33Z

1

Ruby

i1="i.txt"
i2="o.txt"
c1=IO.readlines(i2)
c2=IO.readlines(i1)
File.open(i1){|x|x.puts(c1)}
File.open(i2){|x|x.puts(c2)}

Shortened version:

a=["i.txt","o.txt"]
(0..1).each{|x|b[x]=IO.readlines(a[x])*"\n"}
a.reverse!
(0..1).each{|x|IO.write(a[x],b[x])}

Not the shortest, but very simple and easy to read. Also, no intermediate files, only RAM.

edited Jun 17 '20 at 9:04

Community♦

1

answered Dec 28 '13 at 20:30

user11485

1

\$\begingroup\$ Given that it’s a code-golf, you could at least take out the spaces and try somewhat for the shortest. \$\endgroup\$ – Ry- Dec 28 '13 at 20:42
\$\begingroup\$ Totally didn't realize it was code-golf, sorry \$\endgroup\$ – user11485 Dec 28 '13 at 21:15

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Eisa Adil · Accepted Answer · 2013-12-28 21:27:11Z

1

PHP

$f1 = 'file1.txt';
$f2 = 'file2.txt';

$f1contents = file_get_contents ($f1);
$f2contents = file_get_contents ($f2);

file_put_contents($f1, $f2contents);
file_put_contents($f2, $f1contents);

answered Dec 28 '13 at 21:27

Eisa Adil

1354 bronze badges

10

\$\begingroup\$ Thats not really golfy :( \$\endgroup\$ – Jakob Bowyer Dec 30 '13 at 11:45

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Darren Stone · Accepted Answer · 2013-12-29 00:16:36Z

1

Shell script, 24

Works in Bash and probably most shells. Pass with your two filenames as parameters.

mv $1 ੴ;mv $2 $1;mv ੴ $2

If you want fixed filenames then this will do it, for a 12 char penalty:

mv i.txt ੴ;mv o.txt i.txt;mv ੴ o.txt

edited Dec 29 '13 at 0:16

answered Dec 29 '13 at 0:08

Darren Stone

5,1321 gold badge14 silver badges27 bronze badges

\$\begingroup\$ @minitech, yes it does. 'ੴ' becomes 'o.txt'. Those are mv operations, not cp. \$\endgroup\$ – Darren Stone Dec 29 '13 at 1:44
\$\begingroup\$ Second best answer so far! Reduce it by two characters and you win! I do not care about fixed filenames. \$\endgroup\$ – user10766 Dec 29 '13 at 4:28

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tamasgal · Accepted Answer · 2013-12-30 11:24:19Z

1

Python:

import os
l,e='i_o'*2,'.txt'
for x,y in zip(l,l[1:])[::2]:
 os.rename(x+e,y+e)

answered Dec 30 '13 at 11:24

tamasgal

1113 bronze badges

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kitcar2000 · Accepted Answer · 2014-05-10 19:13:44Z

1

Windows Batch File (48)

type i.txt>a&type o.txt>i.txt&type a>o.txt&del a

I forgot about the move command when I wrote this...

answered May 10 '14 at 19:13

kitcar2000

2,71712 silver badges24 bronze badges

\$\begingroup\$ You just overwrote my a file! \$\endgroup\$ – Danny May 14 '14 at 16:12
\$\begingroup\$ @Danny The question states that you may create another file, but it must be deleted. \$\endgroup\$ – kitcar2000 May 14 '14 at 16:21

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bacchusbeale · Accepted Answer · 2014-05-11 00:20:32Z

1

C 162

Golfed: uses t.txt as tmp file and swaps names then removes t.txt.

#include <stdio.h>
#define R(x,y) rename(x,y)
#define X(x) remove(x)
int main(){char *i="i.txt",*o="o.txt",*t="t.txt";R(i,t);X(i);R(o,i);R(t,o);X(t);return 0;}

Edit: removed 2 spaces

answered May 11 '14 at 0:20

bacchusbeale

1,2356 silver badges7 bronze badges

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Spedwards · Accepted Answer · 2014-05-11 01:01:11Z

1

PHP - 172

Golfed version of @EisaAdil's answer

$f1='file1.txt';$f2='file2.txt';$f1contents=file_get_contents($f1);$f2contents=file_get_contents($f2);file_put_contents($f1,$f2contents);file_put_contents($f2,$f1contents);

answered May 11 '14 at 1:01

community wiki

Spedwards

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Community · Accepted Answer · 2020-06-17 09:04:33Z

1

Rebol - 46 (rename file) or 55 (r/w contents)

Rename file (using t as temporary file):

r: :rename 
r i: %i.txt %t
r o: %o.txt i
r %t o

Read in then write out file contents:

a: read i: %i.txt
b: read o: %o.txt
write o a 
write i b

edited Jun 17 '20 at 9:04

Community♦

1

answered May 11 '14 at 15:19

draegtun

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Community · Accepted Answer · 2020-06-17 09:04:33Z

1

PHP, 45

<?php
copy('i','t');copy('o','i');rename('t','o');

Not very golfy but shortest PHP so far.

edited Jun 17 '20 at 9:04

Community♦

1

answered May 11 '14 at 12:30

mleko

2881 silver badge8 bronze badges

\$\begingroup\$ file extensions are missing. \$\endgroup\$ – Titus Dec 26 '18 at 9:05

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Michael Easter · Accepted Answer · 2014-05-14 21:47:07Z

Groovy - 99 chars

This is my attempt, with Groovy 2.2.1. I tried to do it without renaming:

f={new File(it+".txt")}
w={x,y->x.withWriter{it.write y}}
i=f "i"
o=f "o"
t=i.text
w i,o.text
w o,t

Ungolfed:

file = { new File(it+".txt") }
writeTextToFile = { x,y -> x.withWriter{it.write y} }

iFile = file("i")
oFile = file("o")

iText = iFile.text
writeTextToFile (iFile,oFile.text)
writeTextToFile (oFile,iText)

jaybee3 · Accepted Answer · 2014-05-15 12:31:41Z

1

VBA (148...132) and (126...110)

Renaming with a temp file t in the c:\ drive. Also first attempt at golf :S

Sub s():Set f=CreateObject("Scripting.FileSystemObject"):i="c:\i.txt":t="c:\t":f.MoveFile i,t:f.MoveFile "c:\o.txt",i:Kill t:End Sub

If scrrun.dll is referenced already, could cut it down a bit to 126...110.

Sub s():Set f=new FileSystemObject:i="c:\i.txt":t="c:\t":f.MoveFile i,t:f.MoveFile "c:\o.txt",i:Kill t:End Sub

edited May 15 '14 at 12:31

answered May 15 '14 at 9:13

jaybee3

112 bronze badges

\$\begingroup\$ Looks like your code has a lot of whitespace. Are you sure they are needed? You can have a much better score if you remove them. \$\endgroup\$ – user12205 May 15 '14 at 10:27
\$\begingroup\$ I don't think it's needed the editor just threw it in. Removed apart from where it's necessary :) \$\endgroup\$ – jaybee3 May 15 '14 at 12:32

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Fors · Accepted Answer · 2014-05-16 00:58:32Z

C: 65 characters

#define r(a,b)rename(#a".txt",#b".txt");
main(){r(i,)r(o,i)r(,o)}

A quite simple solution in C that does the job. It uses a temporary name (.txt) for one of the files before giving it its proper new name.

Ungolfed (note how the syntax highlighting fails in the define, a bug has been uncovered!):

#include <stdio.h>

#define r(a, b) rename(#a ".txt", #b ".txt");

int main()
{
    r(i,  ) // rename("i.txt",  ".txt");
    r(o, i) // rename("o.txt", "i.txt");
    r( , o) // rename( ".txt", "o.txt");

    return 0;
}

Heiko Oberdiek · Accepted Answer · 2014-05-17 01:20:47Z

Perl, 120 bytes (Contents swapping without file renaming)

use open IO,':bytes';undef$/;open I,"<i.txt";$I=<I>;open I,"<o.txt";open O,">i.txt";print O<I>;open O,">o.txt";print O$I

The file contents is put into memory and written back to the other file. Thus i.txt and o.txt must fit into memory.

Since the file contents are actually exchanged, hard links are updated automatically, see AJManfield's comment.

Ungolfed:

use open IO => ':bytes'; # binmode, not needed for Unix, but needed for Windows
undef $/;                # read whole file instead of lines
open I, "<i.txt";        # open i.txt for reading
$I = <I>;                # read i.txt
open I, "<o.txt";        # open o.txt for reading
open O, ">i.txt";        # open i.txt for writing
print O <I>;             # read o.txt and put the contents in i.txt
open O, ">o.txt";        # open o.txt for writing
print O $I;              # write o.txt with contents of old i.txt

peter ferrie · Accepted Answer · 2017-11-27 20:14:53Z

1

Windows Batch, 39 bytes

ren i.txt x&ren o.txt i.txt&ren x o.txt

answered Nov 27 '17 at 20:14

peter ferrie

1,0157 silver badges15 bronze badges

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cyclaminist · Accepted Answer · 2018-12-24 03:34:06Z

Lua, 71 70 bytes

_ENV=os t='.txt'i,o,r='i'..t,'o'..t,rename r(i,t)r(o,i)r(t,o)remove(t)

Try it online!

Define os, the operating system library, as the global table so we can write rename and remove instead of os.rename and os.remove. (Incidentally this also means the one-letter variables are actually fields in the os table.) Make short alias for os.rename to save some space. Set up filename variables, using '.txt' as temporary file. Do the renaming and deleting.

Community · Accepted Answer · 2020-06-17 09:04:33Z

1

PHP, 52 bytes

AsksAnyway´s php modernized & golfed:

($r=rename)(i.$e=".txt",x);$r(o.$e,i.$e);$r(x,o.$e);

Run with php -nr '<code>'.

edited Jun 17 '20 at 9:04

Community♦

1

answered Dec 26 '18 at 9:08

Titus

14.2k1 gold badge15 silver badges41 bronze badges

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sergiol · Accepted Answer · 2019-01-25 14:48:11Z

1

Tcl, 122 bytes

set A [read [open i.txt]]
puts [set i [open i.txt w]] [read [open o.txt]]
puts [set o [open o.txt w]] $A
close $i
close $o

Try it online!

Tcl, 169 bytes

set A [read [set i [open i.txt r]]] set B [read [set o [open o.txt r]]] close $i close $o puts [set i [open i.txt w]] $B puts [set o [open o.txt w]] $A close $i close $o

Try it online!

edited Jan 25 '19 at 14:48

answered Dec 24 '18 at 0:06

sergiol

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Community · Accepted Answer · 2020-06-17 09:04:33Z

0

SmileBASIC, 36 35 bytes

@L
RENAME@OI[2-I],@IO[I]I=I+1GOTO@L

edited Jun 17 '20 at 9:04

Community♦

1

answered Dec 26 '18 at 3:11

12Me21

6,3601 gold badge18 silver badges37 bronze badges

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Swap contents of two files

24 Answers 24

zsh, 20

Python, 77

Python, 65

Python, 63

PHP, 68

Windows Batch File, 42

Windows Batch File (args), 30

Two bash based ansers; 52 and 62 chars

shell: diff + patch (+ tee + sed...) 52

Sample run

use of xargs to simplify `mv` requests

PHP, 89

Ruby, 72 bytes

Powershell, 44 49 bytes

Ruby

Shell script, 24

Windows Batch File (48)

C 162

Rebol - 46 (rename file) or 55 (r/w contents)

PHP, 45

Groovy - 99 chars

VBA (148...132) and (126...110)

C: 65 characters

Perl, 120 bytes (Contents swapping without file renaming)

Windows Batch, 39 bytes

Lua, 71 70 bytes

PHP, 52 bytes

Tcl, 122 bytes

Tcl, 169 bytes

SmileBASIC, 36 35 bytes

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Swap contents of two files

24 Answers 24

zsh, 20

Python, 77

Python, 65

Python, 63

PHP, 68

Windows Batch File, 42

Windows Batch File (args), 30

Two bash based ansers; 52 and 62 chars

shell: diff + patch (+ tee + sed...) 52

Sample run

use of xargs to simplify mv requests

PHP, 89

Ruby, 72 bytes

Powershell, 44 49 bytes

Ruby

Shell script, 24

Windows Batch File (48)

C 162

Rebol - 46 (rename file) or 55 (r/w contents)

PHP, 45

Groovy - 99 chars

VBA (148...132) and (126...110)

C: 65 characters

Perl, 120 bytes (Contents swapping without file renaming)

Windows Batch, 39 bytes

Lua, 71 70 bytes

PHP, 52 bytes

Tcl, 122 bytes

Tcl, 169 bytes

SmileBASIC, 36 35 bytes

Your Answer

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use of xargs to simplify `mv` requests