Ferran Eloi

#!/bin/bash
# swap.sh   Function to perform the swap of 2 variables contents
# Copyright (C) 2010  Author: Ferran Eloi Gutiérrez Martos <ferraneloi at gmail dot com>
#
# Last Modified: 2010-15-10
# Usage and comments: You can just source the file and use the function.
#
# This code is released AS-IS, under an GPL license. The GPL license can be
# found at http://www.gnu.org/licenses/gpl.html and is included
# for your convenience at the bottom of the swap function.
##
swap () {
local x=\$"$1"   # Name of the variable of the 1st parameter
local y=\$"$2"   # Name of variable passed as 2nd parameter
local valueofx=`eval "expr \"$x\" "`  #contents of 1st variable
local valueofy=`eval "expr \"$y\" "`  #contents of 2nd variable
eval "$1=\"$valueofy\""
eval "$2=\"$valueofx\""
}
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
# Main program to test the function
#Example of use 1: Simple swaps
a=3
b=8
c=12
echo "Example 1: Simple swaps"
echo "Initial var. values" "a="$a "b="$b "c="$c
swap a b  #we swap content of variables a and b
echo "Perform Swap (a,b) " "a="$a "b="$b "c="$c
swap a c  #now we swap  a and c
echo "Perform Swap (a,c) " "a="$a "b="$b "c="$c
#Example of use 2:  Sorting ascending elements
a=12
b=8
c=5
echo "Example 2: Simple sorting of 3 values"
echo "Initial var. values" "a="$a "b="$b "c="$c
if [ $a -gt $b ]
then
swap a b
fi
if [ $a -gt $c ]
then
swap a c
fi
if [ $b -gt $c ]
then
swap b c
fi
echo "Final Ascending sort:" "a="$a "b="$b "c="$c