CODEWITHSUNDEEP
stringperlreplace
Richard
Richard

Reputation: 7000

Perl string replacements of file paths in text file

I'm trying to match file paths in a text file and replace them with their share file path. E.G. The string "X:\Group_14\Project_Security" I want to replace with "\\Project_Security$".

I'm having a problem at getting my head around the syntax, as I have use the backslash (\) to escape another backslash (\\) but this does not seem to work for matching a path in a text file.

open INPUT, '< C:\searchfile.txt';
open OUTPUT, '> C:\logsearchfiletest.txt';
@lines = <INPUT>;
%replacements = (
    "X:\\Group_14\\Project_Security" => "\\\\Project_Security\$",
    ...
    (More Paths as above)
    ...
);
$pattern = join '|', keys %replacements;
for (@lines) {
    s/($pattern)/@{[$replacements{$1}]}/g;
    print OUTPUT;
}

Not totally sure whats happening as "\\\\Project_Security\$" appears as \\Project_Security$" correctly.

So I think the issues lies with "X:\\Group_14\\Project_Security" not evaluating to
"X:\Group_14\Project_Security" correctly therefore not match within the text file?

Any advice on this would be appreciated, Cheers.

Upvotes: 1

Views: 103

Answers (3)

Adi Inbar
Adi Inbar

Reputation: 12323

I see you've posted my rusty Perl code here, how embarrassing. ;) I made an update earlier today to my answer in the original PowerShell thread that gives a more general solution that also handles regex metacharacters and doesn't require you to manually escape each of 600 hash elements: PowerShell multiple string replacement efficiency. I added the perl and regex tags to your original question, but my edit hasn't been approved yet.

[As I mentioned, since I've been using PowerShell for everything in recent times (heck, these days I prepare breakfast with PowerShell...), my Perl has gotten a tad dusty, which I see hasn't gone unnoticed here. :P I fixed several things that I noticed could be coded better when I looked at it a second time, which are noted at the bottom. I don't bother with error messages and declarations and other verbosity for limited use quick-and-dirty scripts like this, and I don't particularly recommend it. As the Perl motto goes, "making easy things easy and hard things possible". Well, this is a case of making easy things easy, and one of Perl's main advantages is that it doesn't force you to be "proper" when you're trying to do something quick and simple. But I did close the filehandles. ;)

Upvotes: 0

shawnhcorey
shawnhcorey

Reputation: 3601

Some notes:

  • Always use the 3-argument open
  • Always check for errors on open, print, or close
  • Sometimes is easier to use a loop than clever coding

Try:

#!/usr/bin/env perl

use strict;
use warnings;

# --------------------------------------

use charnames qw( :full :short   );
use English   qw( -no_match_vars );  # Avoids regex performance penalty

use Data::Dumper;

# Make Data::Dumper pretty
$Data::Dumper::Sortkeys = 1;
$Data::Dumper::Indent   = 1;

# Set maximum depth for Data::Dumper, zero means unlimited
local $Data::Dumper::Maxdepth = 0;

# conditional compile DEBUGging statements
# See http://lookatperl.blogspot.ca/2013/07/a-look-at-conditional-compiling-of.html
use constant DEBUG => $ENV{DEBUG};

# --------------------------------------

# place file names in variables to they are easily changed
my $search_file     = 'C:\\searchfile.txt';
my $log_search_file = 'C:\\logsearchfiletest.txt';

my %replacements = (
  "X:\\Group_14\\Project_Security" => "\\\\Project_Security\$",
  # etc
);

# use the 3-argument open as a security precaution
open my $search_fh,     '<', $search_file     or die "could not open $search_file: $OS_ERROR\n";
open my $log_search_fh, '>', $log_search_file or die "could not open $log_search_file: $OS_ERROR\n";

while( my $line = <$search_fh> ){

  # scan for replacements
  while( my ( $pattern, $replacement ) = each %replacements ){
    $line =~ s/\Q$pattern\E/$replacement/g;
  }

  print {$log_search_fh} $line or die "could not print to $log_search_file: $OS_ERROR\n";
}

# always close the file handles and always check for errors
close $search_fh     or die "could not close $search_file: $OS_ERROR\n";
close $log_search_fh or die "could not close $log_search_file: $OS_ERROR\n";

Upvotes: 1

Muttley
Muttley

Reputation: 263

If all the file paths and replacements are in a similar format to your example, you should just be able to do the following rather than using a hash for looking up replacements:

for my $line (@lines) {
    $line =~ s/.+\\(.+)$/\\\\$1\$/;
    print OUTPUT $line;
}

Upvotes: 1

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