Perl - Grep function regular expression Post: 302446609

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Top Forums Shell Programming and Scripting Perl - Grep function regular expression Post 302446609 by thegeek on Thursday 19th of August 2010 08:07:06 AM

08-19-2010

Banned

Everything you have checked is right.. Understand as mentioned below.

Quote:

Originally Posted by adelsin

For some reason,
@logs is a list of log files
@filter is a list of expressions to grep out

Code:

foreach (@logs){
open READ, "<$_" or die $!;
@temp=<READ>;
close READ;

    foreach (@filter){
        print grep /$_/,@temp ;    
        
}
}

returns a regex error in one of the files it's parsing.

When the file has a line with just single open paranthesis, then you will get regex error ?! What is the big deal in this ?

If you want to avoid then escape it using either quotemeta function, or use \Q. Using some input directly as regex is not good, as you have this risk.

Quote:

Originally Posted by adelsin

while

Code:

print grep $_,@temp ;

returns the entire file

What does grep will do ? If for current iteration the return value is true then the current $_ will be pushed in to the result array, so you get the entire array, as each time you have some value at $_ and that returns true.

Quote:

Originally Posted by adelsin

while

Code:

print grep /string/,@temp ;

works fine.

I can not seem to wrap my head around it today. Any clues?

If you dont understand the basics, you will end up in confusions.

thegeek

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