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Re: bash null conditional



Craig White wrote:
I'm in my bash book and looking on web but can't seem to resolve this
simple problem.

$ if [ -n "grep A121 myfile.csv" ]; then echo "null"; fi
null

$ if [ -n "grep A125 myfile.csv" ]; then echo "null"; fi
null

A125 definitely is null when I just run the grep command in the quotes
but A121 definitely is not null.

What am I missing on the if/null operator here?

Craig


I think it's simple:

The if sequence is only testing if the strings "grep A121 myfile.csv" or "grep A125 myfile.csv" have a non zero lentgh, and both strings have definitively non zero length. No grep cmd is executed.

If you want the grep commands to be executed and check the grep output, you must use $(grep ...) or `grep ...`.

--

Joachim Backes <joachim backes rhrk uni-kl de>

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