Unix in a Nutshell, 4th Edition

Name

if

Synopsis

    if condition1
    then commands1
    [ elif condition2
     then commands2 ]
     .
     .
     .
    [ else commands3 ]
    fi

If condition1 is met, do commands1; otherwise, if condition2 is met, do commands2; if neither is met, do commands3. Conditions are often specified with the test and [[ ]] commands. See test and [[ ]] for a full list of conditions, and see additional Examples under : and exit.

Examples

Insert a 0 before numbers less than 10:

    if [ $counter -lt 10 ]
    then number=0$counter
    else number=$counter
    fi

Make a directory if it doesn’t exist:

    if [ ! -d $dir ]; then
       mkdir $dir
       chmod 775 $dir
    fi