if condition

furqan_sindhu · 09-22-2007, 05:17 AM

hello people !!!

i have a variable named "word"

what would be the condition to check whether that word is empty, i mean to return true if word=""

????

colucix · 09-22-2007, 05:28 AM

In Bash the test is -z, as in

Code:

if [ -z $pippo ] ; then
   echo empty variable: pippo
fi

See man test for details and any other available expression.

furqan_sindhu · 09-22-2007, 05:40 AM

great, that worked!!

What's the difference in your solution and the following

Code:

if [ $word != "" ]

and please also tell how can i check whether a file contains some specific words ???

Any link, any idea for that ???

druuna · 09-22-2007, 06:16 AM

Hi,

If word is not set, then if [ $word != "" ] will resolve to: if [ != "" ]. As a result bash will throw an error ([: !=: unary operator expected) because there is nothing to check against.
If word is set, then there are values to the left and to the right of the check (!= in this case) and bash can do its thing.

The -z option is specially made to check empty (zero) variables.

You can use grep to check if a string is present in a file: grep "something" infile. See grep's manpage for details.

Hope this helps.

RenRen · 09-22-2007, 06:50 AM

I don't understand what you're all talking about . . . . . .

druuna · 09-22-2007, 06:56 AM

Hi,

@RenRen: And the question is??

If you have a specific question we can help you, but these comments don't add to this (or any) thread.