What's wrong with this line: if ${TEST:?} ; then echo empty; fi - UNIX for Dummies Questions & Answers

meili100 · #1 (**permalink**) 02-22-2008

I want to print "empty" if $TEST is empty.

TEST=
if ${TEST:?} ; then echo empty; fi

But it doesn't work. What's wrong?

zazzybob · #2 (**permalink**) 02-23-2008

Code:

$ cat > foo.ksh
#!/bin/ksh
TEST=
FOO=${TEST:?empty}
$ chmod +x ./foo.ksh$ ./foo.ksh
./foo.ksh: line 3: TEST: empty
$ sed 's/^TEST=/TEST=something/' foo.ksh > foo2.ksh
$ chmod +x ./foo2.ksh
$ ./foo2.ksh
$

No need for the conditional structure, a simple variable assignment will do it.

Cheers,
ZB

fpmurphy · #3 (**permalink**) 02-23-2008

${TEST:?} will cause your script to exit immediately. If you want to exit more
gracefully or do some cleanup, the following method of testing for an null or
empty string may be more useful.

Code:

#!/usr/bin/ksh

TEST=

if [[ ! $TEST ]]
then
   echo "empty"
fi

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