On 06/10/2013 01:59 PM, dte...@freebsd.org wrote:
-----Original Message-----
From: owner-freebsd-questi...@freebsd.org [mailto:owner-freebsd-
questi...@freebsd.org] On Behalf Of lcon...@go2france.com
Sent: Monday, June 10, 2013 11:53 AM
To: freebsd-questions@freebsd.org
Subject: Bourne shell "if" syntax
script fragment:
PTR=`dig @some.dns +short +norec -x a.b.c.d`
echo "$PTR"
if [ "$PTR" == "" ] ; then
if [ "$PTR" = "" ]; then
or
if [ -z "$PTR" ]; then
or
if [ "$PTR" ]; then
but _NOT_
if [ "$PTR" == "" ]; then
I work across a bunch of different OSs and shells of many vintages. As I
recall,
the -z argument has problems of portability on older/broken shells and/or
is not available in all environments (I cannot recall which at the moment). So
I achieve the same results by using a character sentinel that guarantees that
the
comparison always works:
f [ _"$PTR" == _ ] ; then
--
-----------------------------------------------------------------------
Tim Daneliuk
_______________________________________________
freebsd-questions@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-questions
To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
