SPUG: Where is grep's return value?

Asim Jalis asimjalis at acm.org
Tue Sep 10 18:18:35 CDT 2002

On Tue, Sep 10, 2002 at 06:27:32PM -0400, Orr, Chuck  (NOC)
> I have something that looks like this:
> if (grep("$KEY",EXISTING)){
> In the event that this is true, I want to print the data that
> makes it true. In other words, I want to print the line from
> EXISTING that contains the pattern from the variable $KEY.  The
> problem I am having is figuring out where that line is.  Is it
> stored in a variable I don't know about?  If not, how can I
> obtain this data?  I realize this is a pretty basic question,
> but I am having a tough time finding the answer and I need to
> get this done. Any suggestions/help would be greatly
> appreciated.

The first argument to grep seems wrong. If $KEY contains a
regular expression pattern you should use grep(/$KEY, @EXISTING).

Otherwise Perl will evaluate the string "$KEY" which will
evaluate to true in all cases except when $KEY is 0 or "" or

Assuming $KEY contains a regular expression pattern you can print
out all the elements in @EXISTING that match it using:

print join "\n" => grep { /$KEY/ } @EXISTING;


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