Re: [SLE] Bash Q: how to keep a script from failing when a var is undef or empty

JW writes:

TAPESTATE=`mt -f /dev/st0 status | head -2 |tail -1 | cut -d " " -f4`

if [ ${TAPESTATE} == "512" ]; then READY="yes" else READY="no" && echo "No tape in oe1 tape drive" | mail -s "Oe1 tape error" jw@mailsw.com fi

A general way to test for a non-empty string is: if [ -n "${TAPESTATE}" ]; then ... fi Or its converse, to test for an empty string: if [ -z "${TAPESTATE}" ]; then ... fi See "man test". The left bracket [ is the same thing as the "test" command. -Ti