Need to search for a string in a file

akrrs7 has asked for the wisdom of the Perl Monks concerning the following question:

Hello, I need to search for a certain string in a file. It has to be the first character in the line (if it is 2nd or later - don't get it). If the string is found, I have to get the value after the delimiter - (= equal). eg: Generated filename=a_b_c.xml Search for 'Generated filename' and return the value a_b_c.xml.Also G has to be the 1st character in the line. I have a basic code snippet:

my $logFile =  "someFile.log";
    my $stringToFind = "Generated filename";
    open logFile, $logFile or die $!;
    my @list = grep /\b$stringToFind\b/, <logFile>;
    chomp @list;
    print "$_\n" foreach @list;
[download]

However, I am clueless how to ensure that G is the first character and to return the value after the equal sign. Thanks

Comment on Need to search for a string in a file Download Code

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Re: Need to search for a string in a file by Utilitarian (Vicar) on Oct 20, 2011 at 10:43 UTC
You needn't pull the whole file into memory just to search for one line. The caret character,(^), means start of the line in a regex. Read perlre, these meta-characters is the second subject covered. You can match save and exit the loop in one statement. `sub get_file_from_log(){ my $log_name=shift; open(my $log_file, "<", $log_name); my $file_name; while (<logFile>){ last if ($file_name) = /^Generated filename\s=\s(.+)$/; } return $file_name; }` [download] `print "Good ",qw(night morning afternoon evening)[(localtime)[2]/6]," fellow monks."`	[reply] [d/l] [select]
Re^2: Need to search for a string in a file by jwkrahn (Abbot) on Oct 20, 2011 at 20:38 UTC
`sub get_file_from_log(){ my $log_name=shift; open(my $log_file, "<", $log_name);` [download] Your prototype says to accept NO arguments but your next line says to accept ONE argument. You should not use prototypes! You should always verify that open worked correctly before trying to use a possibly invalid filehandle. `open(my $log_file, "<", $log_name); my $file_name; while (<logFile>){` [download] You are opening the filehandle `$log_file` but you are trying to read from the filehandle `logFile`?	[reply] [d/l] [select]
Re^2: Need to search for a string in a file by akrrs7 (Acolyte) on Oct 20, 2011 at 11:51 UTC
Hello Utilitarian...works like a charm. Thanks. I've read perlretut and perlre but still fumble. I will slowly get the hang as I keep writing code. Perl is not as intuitive to me as C++ and Java. Thanks a lot.....	[reply]
Re^3: Need to search for a string in a file by aartist (Pilgrim) on Oct 20, 2011 at 14:19 UTC
Perl is not as intuitive to me . You will find your way here. The terminology slightly is different, but there is always more than one way to do it in Perl, which provides extended expressibility.	[reply]
Re^2: Need to search for a string in a file by anneli (Pilgrim) on Oct 20, 2011 at 21:25 UTC
~~Will `my @list = grep /re/, <FH>` necessarily pull the entire file into memory? (I don't know and would like to know for sure!)~~ It sure seems to! `open my $fh, "<", "/dev/urandom" or die "$!"; my @a = grep /huh, whaddayamean/, <$fh>;` [download]	[reply] [d/l] [select]
Re^3: Need to search for a string in a file by aaron_baugher (Curate) on Oct 20, 2011 at 22:29 UTC
Someone please correct me if I'm wrong, but I don't think your example will pull the entire file into memory. I think it will read lines from $fh one at a time, passing them to grep, which will return matching lines to @a. However, you're reading from `/dev/urandom`, which is an endless stream of random bytes, not a file which has an end. So eventually @a is going to get very large, yes. Also, depending on what your end-of-line delimiter is set to, `<$fh>` may return some very long lines for grep to deal with.	[reply] [d/l] [select]
Re^4: Need to search for a string in a file by anneli (Pilgrim) on Oct 20, 2011 at 23:07 UTC
Re^5: Need to search for a string in a file by aaron_baugher (Curate) on Oct 21, 2011 at 18:36 UTC
Re: Need to search for a string in a file by moritz (Cardinal) on Oct 20, 2011 at 10:27 UTC
Please read perlretut, it answers at least one of your questions, probably both. Perl 6 - second systems done right	[reply]
Re: Need to search for a string in a file by Anonymous Monk on Oct 20, 2011 at 10:44 UTC
`perl -lne " print $1 if /^([^=]+)=/ " < infile > outfile "`	[reply] [d/l]


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