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

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


Insert a 0 before numbers less than 10:

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

Make a directory if it doesn't exist:

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

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