How can I trim the contents of a file in Perl?

Question

I would like to remove contents of a file from a certain character to a certain character in the file in Perl. How do I do that using a script?

The file has this:

Syslog logging: enabled (11 messages dropped, 2 messages rate-limited,
                0 flushes, 0 overruns, xml disabled, filtering disabled)
    Console logging: level informational, 81 messages logged, xml disabled,
                     filtering disabled
    Monitor logging: level debugging, 0 messages logged, xml disabled,
                     filtering disabled
    Buffer logging: level informational, 28 messages logged, xml disabled,
                    filtering disabled
    Logging Exception size (4096 bytes)
    Count and timestamp logging messages: disabled

No active filter modules.

    Trap logging: level informational, 83 message lines logged

Log Buffer (4096 bytes):

*Oct  4 13:42:03.210: %SEC_LOGIN-5-LOGIN_SUCCESS: Login Success [user: ] [Source: ] [localport: ] at UTC Mon Oct 4 2010

And the new file after the trimming should be this

*Oct  4 13:42:03.210: %SEC_LOGIN-5-LOGIN_SUCCESS: Login Success [user: ] [Source: ] [localport: ] at UTC Mon Oct 4 2010

Answer 1

Hmm, the question is not very clear. I guess you want to delete certain strings in a file.

#!/usr/bin/perl

$filename = $ARGV[0];
$a = $ARGV[1];
$b = $ARGV[2];

open (FILE, $filename) || die ("Can't open the file");
open (INFILE, ">$filename.tmp") || die ("Can't open the temp file");

while ($line = <FILE>) {
    $line =~ s/$a.*$b/$a$b/g;
    print INFILE $line
}
close (INFILE);
close (FILE);

I guess what you are expecting is in here "$line =~ s/$a.*$b/$a$b/g;" It only replaces the content between the string but not the actual string. You could simply call sed script

sed 's/a.*b/ab/g' file

Answer 2

If i well understand your needs, you can do something like :

I've updated according to your new specifications

#!/usr/bin/perl
use strict;
use warnings;

my $in_file = 'foo.txt';
my $out_file = 'bar.txt';

open my $fh_in, '<', $in_file or die "unable to open '$in_file' for reading: $!";
open my $fh_out, '>', $out_file or die "unable to open  '$out_file' for writing: $!";

while(<$fh_in>) {
    chomp;

    # updated according to new requirements
    next if (/^Syslog logging/ .. /^Log Buffer/);
    next if (/^$/);

    print $fh_out $_,"\n";
}
close $fh_in;
close $fh_out;

This script reads the file foo.txt and write lines into file bar.txt except those between begin_skip and end_skip included.

begin_kip and end_skip can be any regex.

Answer 3

You don't give anywhere near enough information. But it sounds like something that can be done from the command line. Your solution will probably look something like this:

$ perl -ne 'print unless /start_skip/ .. /end_skip/' in.txt > out.txt

Update: Having seen your expanded explanation, it looks like you only want lines that start with an asterisk.

$ perl -ne 'print if /^\*/' in.txt > out.txt