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Revision: 10735
at January 11, 2009 21:06 by jaduks
Initial Code 
The syntax:

VARIABLE=${1:-DEFAULTVALUE} #set VARIABLE with the value of 1st Arg to the script,
                            #If 1st arg is not entered, set it to DEFAULTVALUE


#One simple bash script code:

...
tmpdir=/tmp
defvalue=1

DIR=${1:-$tmpdir} # Defaults to /tmp dir.
VALUE=${2:-$defvalue} # Default value is 1.

echo $DIR
echo $VALUE
..


Now while running the script, specify values for both the arguments.
$ ./defvaue.sh /dev 23
/dev
23

This time don't mention their values.
$ ./defvaue.sh
/tmp
1

so

DIR=${1:-$tmpdir}
VALUE=${2:-$defvalue}

is a replacement for the following:

[ -z $1 ] && DIR="/tmp"
[ -z $2 ] && VALUE=1
Initial URL 
http://unstableme.blogspot.com/2007/12/setting-default-value-for-shell.html
Initial Description 
To see how we can set default values for bash script variables inside bash script
Initial Title 
Setting default value for BASH variable
Initial Tags 
Bash
Initial Language 
Bash