Shortest way to swap two files in bash

Question

Can two files be swapped in bash?

Or, can they be swapped in a shorter way than this:

cp old tmp
cp curr old
cp tmp curr
rm tmp

Answer 1

Surely mv instead of cp?

Answer 2

$ mv old tmp && mv curr old && mv tmp curr

is slightly more efficient!

Answer 3

mv old tmp
mv curr old
mv tmp curr

Answer 4

You could simply move them, instead of making a copy.

#!/bin/sh
# Created by Wojtek Jamrozy (www.wojtekrj.net)
mv $1 cop_$1
mv $2 $1
mv cop_$1 $2

http://www.wojtekrj.net/2008/08/bash-script-to-swap-contents-of-files/

Answer 5

using mv means you have one fewer operations, no need for the final rm, also mv is only changing directory entries so you are not using extra disk space for the copy.

Temptationh then is to implementat a shell function swap() or some such. If you do be extremly careful to check error codes. Could be horribly destructive. Also need to check for pre-existing tmp file.

Answer 6

Just to explain, the reason mv is much faster than cp, is that mv just changes directory entries, while cp actually copies the whole file contents.

Answer 7

tmpfile=$(mktemp $(dirname "$file1")/XXXXXX)
mv "$file1" "$tmpfile"
mv "$file2" "$file1"
mv "$tmpfile" "$file2"

Answer 8

Add this to your .bashrc:

function swap()         
{
    local TMPFILE=tmp.$$
    mv "$1" $TMPFILE
    mv "$2" "$1"
    mv $TMPFILE "$2"
}