http://www.perlmonks.org?node_id=38279

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

Let's assume that I have a text file with the following format: 
# This is a commented line
# blah blah blah
:data
:data

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Well, I've been able to read the file into a scaler. Now i'd like to strip all the comment lines (prefixed by "#") out of the scaler before I move on and do anything else. For the sub routine, I am useing the following code: 

sub get_info {
  my $infile = "template.dsc";
  open (INFILE, "$infile") || die "Broken: $!";

  my $content;
  while (<INFILE>) {
    $content .= $_;
  };

  # Remove Comments?


  close (INFILE);
  return $content;
};

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Please help me get rid of that unwanted data (but I need to keep it in the text file for the idiots who use it).

Originally posted as a Categorized Question.

Replies are listed 'Best First'.
Re: How do I strip lines prefixed by a
by runrig (Abbot) on Oct 25, 2000 at 07:32 UTC
    Simplest is to: 
    while (<INFILE>) {
    next if /^#/;
    # or
    next if substr($_,0,1) eq '#';
    $content .= $_;
};

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[d/l]
      Ok....that works great!

      But I am (unfortunately) a beginner Perl Hacker. So could you (or someone) please explain what exactly you did?

      I think it's the ^ that confuses me a bit.

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Re: How do I strip lines prefixed by a
by Fastolfe (Vicar) on Oct 25, 2000 at 20:19 UTC
    Generally when I'm reading files that have the potential for comments or blank lines, a simple regular expression or two does the trick: 
    while (<DATA>) {
   s/\s#.*//;
   next unless /\S/;
   do_something($_);
}

__DATA__
# This is my file
# with a few lines of comments

data=here        # another comment
more=data
                 # more comments
and=more

# end of file

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[d/l]
      That first regexp should have read: s/\s*#.*//;
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[d/l]
Re: How do I strip lines prefixed by a
by Anonymous Monk on Apr 03, 2001 at 23:15 UTC
    Use grep:

    @code_lines = grep !/^#/, @all_lines;

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    The above code is taken directly from the Camel head book.

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[d/l]
Re: How do I strip lines prefixed by a
by pppaulll (Initiate) on Nov 29, 2001 at 21:23 UTC
    This bypasses lines where # is in column 1 and blank lines. 
    STLOAD: foreach $line (<INFILE>) {
    chomp $line;
    $line_header = substr($line, 0, 1);

        # Ignore comments (#) and blank lines
        # including 0-n spaces.
    if ($line_header eq '#' || $line =~ /^ *$/) {
        next STLOAD;
    }
    elsif ($line_header eq '@') {
    # Specifies: targ host, path, file
            $ts_cnt ++;
            if ($ts_cnt > 1) 
        ...

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[d/l]
Re: How do I strip lines prefixed by a
by runrig (Abbot) on Oct 25, 2000 at 07:55 UTC
    Another option:
    my $infile = "template.dsc";
open (INFILE, "$infile") || die "Broken: $!";
my $content;
read INFILE, $content, -s INFILE;
$content =~ s/^#.*//m;
close INFILE;
...

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[d/l]
      correction: make that s/...//gm; oops! forgot the 'g' :-)
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Re: How do I strip lines prefixed by a
by tachyon (Chancellor) on Feb 27, 2003 at 13:21 UTC
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[d/l]
Re: How do I strip lines prefixed by a
by mslattery (Initiate) on Apr 19, 2002 at 18:55 UTC
    KISS

    next if /^\#/ ;

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    thanks,
    mslattery

    Originally posted as a Categorized Answer.

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[d/l]
Re: How do I strip lines prefixed by a
by Anonymous Monk on Feb 27, 2003 at 11:45 UTC
    you can use the bash grep running externally grep -v '^#' file
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      Administrator@C ~
$ cat t
one
#two
#three
four
#five
six

Administrator@C ~
$ perl -ne 'print if not m/^#.*/' <t
one
four
six
      (or in K: 
      x@&~"#"=*:'x
      )
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