Variable explanation x$var=x

[AnotherAlan]

Guys,

I have seen this construct in a number of our scripts but have no idea what the final value should be. Can someone provide an explanation please.

I do understand the test and the variable assignments, just not the x$RET = x part. What does x represent?
All help very much appreciated.

RET=`$RCMD $TGT_HOST date 2>/dev/null`
if [[ x$RET = x ]]; then

Thanks
Alan

 

[Ogzilal]

Hi,

This is a trick for testin if a variable is NULL because some old versions of shells cannot use "" to delimit a NULL string. You can use any character you want not only x
these tests ar equivalent

if [ "$RET" = "" ]
then
 print '$RET is empty'
fi

if [ z$RET = z ]
then
 print '$RET is empty'
fi

 

[AnotherAlan]

Excellent, thanks very much for the info aau.
Much appreciated.
Alan