Setting a variable in bash if it is not defined

Aug 19, 2004

Update: An anonymous commenter pointed out that bash has the ability to do this in a much shorter way:

BLAH=${BLAH:-no}

Job done!, my original older way is below…

[root@sn-b02 init.d]# echo $BLAH

[root@sn-b02 init.d]# [ "${BLAH}" = "" ] && export BLAH="no"
[root@sn-b02 init.d]# echo $BLAH
no
[root@sn-b02 init.d]#