guyov1 has asked for the wisdom of the Perl Monks concerning the following question:

Hello, I have written a code in Perl. I wanted to know how do I refer to the command line arguments as my input/output files. My code: 
#!/usr/intel/bin/perl
use warnings;
use strict;

my $find_flag;                            #using a flag variable

while ( <> ){
  if (/^\S/){                             #match a line that start wit
+h no space
    if (/^\w+clk\[\d+\]/){                #match requested headline
      $find_flag = 0;
    }
    else{
      $find_flag = 1;
    }
  }
  next if $find_flag and /\s+QUALIFIED_CLOCK/;     #skips the line req
+uested
  print qq{$_};                                    #printing ordinary 
+line
}

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The command line should be of the form: CODENAME INPUTFILE OUTPUTFILE STRING so my code will edit INPUTFILE, print the result to OUTPUTFILE and replace "QUALIFIED_CLOCK" with STRING. Thanks!

Replies are listed 'Best First'.
Re: Command Line
by toolic (Bishop) on Oct 22, 2008 at 12:39 UTC
    An alternative is to use the core module, Getopt::Long, to handle the processing of command line options. One advantage of named options is that it can be independent of order: 
    codename -repl string -in infile -out outfile

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Re: Command Line
by holli (Abbot) on Oct 22, 2008 at 12:30 UTC 
    #!/usr/intel/bin/perl
use warnings;
use strict;

my $find_flag;                            #using a flag variable

my ($iFile, $oFile, $replacement) = @ARGV;

open my $iHandle, '<', $iFile or die $@;
open my $oHandle, '>', $oFile or die $@;

while ( <$iHandle> ){
  if (/^\S/){                             #match a line that start wit
+h no space
    if (/^\w+clk\[\d+\]/){                #match requested headline
      $find_flag = 0;
    }
    else{
      $find_flag = 1;
    }
  }
  next if $find_flag and s/\s+QUALIFIED_CLOCK/$replacement/;     #skip
+s the line requested
  print $oHandle $_; #printing ordinary line
}

    [download]


    holli, /regexed monk/
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[d/l]
      Great, thanks! Just one thing - I want the third input - STRING , to be the word that I look for and not replace with. If I don't put anything there I want the code to work as it is, and if I do I need it to look for STRING instead of looking for QUALIFIED_CLOCK...
[reply]
        I was trying to replace the line mentioned with 
          next if ( $find_flag and ( if ($replacement == "") { /\s+QUALIFIED_C
+LOCK/ } else { /\s+$replacement/ } ));

        [download]
        But it writes me "syntax error". I cant understand why... What I'm trying to do is check whether I entered a string and then look for it, and If not, look for QUALIFIED_CLOCK .
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Re: Command Line
by gone2015 (Deacon) on Oct 22, 2008 at 12:51 UTC

    OK, you've been shown what to do.

    I was going to suggest that perhaps reading some of the very fine manual would help you... however, when I looked for @ARGV in the online documentation it doesn't exactly leap out at you... but see @ARGV in perlvar. It's an array like any other.

    The <> construct in your fragment is a peice of magic to work through (what remains of) @ARGV treating each item in turn as a file name, opening and reading.

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