Re: Get string for a word in a file after some specific pattern compare

Assuming that it's a word with no spaces, then...

while (<FILE>) {
    last if /TARGET\s?=\s?(\S*)\s/;
}
my $value = $1 || "not found";
[download]

In other words, look for the string of interest (with some possible white space padding), and placeholder the 'word' that follows it up to the next white space. We break the loop if that exists, and the word will be in $1 from the regex. Otherwise, this should be null, and you'll know it's not there.

Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain

Comment on Re: Get string for a word in a file after some specific pattern compare Download Code

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(Ovid) Re(2): Get string for a word in a file after some specific pattern compare by Ovid (Cardinal) on Mar 27, 2001 at 19:09 UTC
If `$1` was set before the while loop and the while loop fails, `$value` will have garbage in it. Cheers, Ovid Join the Perlmonks Setiathome Group or just click on the the link and check out our stats.	[reply]
Re: Re: Get string for a word in a file after some specific pattern compare by jbert (Priest) on Mar 27, 2001 at 19:42 UTC
And the ever-popular: `my $word; { # Memory is cheap...for some applications local $/ = undef; open( FILE, "< $file" ) or die( "Ack: $!" ); my $whole_file = <FILE>; close FILE; # Assume whitespace delimiting ( $word ) = $whole_file =~ /TARGET\s=\s(\S+)/; } # $word is now set to our value or undefined` [download] This slurps the entire file into memory and so isn't generally a good idea, but a variant of this approach is useful for more complex multi-line patterns. Particularly when you can use $/ = '\n\n'; or similar instead of $/ = undef; This can make many parsing jobs easier. Basically, if you find yourself trying to keep state when parsing a multi-line expression, always consider changing the definition of '$/', it is a very powerful tool. For those unfamiliar with this, evaluating `<FOO>` in a scalar context reads one 'line' from the filehandle FOO. The definition of the end of a line is defined by the pattern held in the '$/' variable. You can set this to whatever you want to define your own line-endings. Note bene: Don't use this to hack around DOS/Unix line ending conventions (CRLF versus LF). If you have problems with this look at the 'binmode' function call. Hmm....am I far enough off-topic yet? Time to stop this...	[reply] [d/l] [select]
Re: Re: Get string for a word in a file after some specific pattern compare by chipmunk (Parson) on Mar 30, 2001 at 08:11 UTC
$1 will not contain the word from the regex, because the special regex variables are automatically localized to the enclosing blocks. As perlre explains it: `$<digits> Contains the subpattern from the corresponding set of parentheses in the last pattern matched, not counting patterns matched in nested blocks that have been exited already. (Mnemonic: like \digits.) These variables are all read-only.` [download] Since the while block has been exited, by the time you check $1 it contains the value it held before the while block was executed. Try this instead: `my $value = 'not found'; while (<FILE>) { $value = $1, last if /TARGET\s?=\s?(\S*)\s/; }` [download]	[reply] [d/l] [select]