CODEWITHSUNDEEP
regexperl
Gaurav Rathi
Gaurav Rathi

Reputation: 93

How to update certain part of text file in perl

I have write the code but it is not working fine . I wish to change this "/" to this "\".

use strict;
use warnings;

open(DATA,"+<unix_url.txt") or die("could not open file!");

while(<DATA>){

s/\//\\/g;
s/\\/c:/;
print DATA $_;

}

close(DATA);

my original file is 

/etc/passwd 
/home/bob/bookmarks.xml 
/home/bob/vimrc

expected output is 

C:\etc\passwd
C:\home\bob\bookmarks.xml
C:\home\bob\vimrc

original output is 

/etc/passwd
/home/bob/bookmarks.xml
/home/bob/vimrc/etc/passwd
\etc\passwd
kmarks.xml
kmarks.xml
mrcmrc

Upvotes: 0

Views: 78

Answers (3)

BobH
BobH

Reputation: 86

Trying to read and write the same file, line by line, in a while loop that is reading till the end of that same file, seems very dicey and unpredictable. I'm not at all sure where your file pointers are going to end up each time you try to write. You would be much safer sending your output to a new file (and then moving it to replace your old file afterwards if you wish).

open(DATA,"<unix_url.txt") or die("could not open file for reading!");
open(NEWDATA, ">win_url.txt") or die ("could not open file for writing!");

while(<DATA>){
    s/\//\\/g;
    s/\\/c:\\/;
    #       ^ (note - from your expected output you also wanted to preserve this backslash)
    print NEWDATA $_;
}

close(DATA);
close(NEWDATA);
rename("win_url.txt", "unix_url.txt");

See also this answer: Perl Read/Write File Handle - Unable to Overwrite

Upvotes: 1

Len Jaffe
Len Jaffe

Reputation: 3484

If the point of the exercise is less about using regular expressions, and more about getting things done, I would consider using modules from the File::Spec family:

use warnings;
use strict;
use File::Spec::Win32;
use File::Spec::Unix;
while (my $unixpath = <>) {
  my @pieces = File::Spec::Unix->splitpath($unixpath);
  my $winpath = File::Spec::Win32->catfile('c:', @pieces);
  print "$winpath\n";
}

Upvotes: 1

nowox
nowox

Reputation: 29096

You don't really need to write a program do achieve this. You can use Perl Pie:

perl -pi -e 's|/|\\|g; s|\\|c:\\|;' unix_url.txt

However if you are running on windows and you use Cygwin, I would suggest to use the cygpath tool that convert POSIX paths into Windows paths.

Also you need to quote your paths since it is allowed to have spaces into windows paths. Or, you can escape the space char:

perl -pi -e 's|/|\\/g; s|\\|c:\\|; s| |\\ |g;' unix_url.txt

Now concerning your initial question, if you still want to use your own script you can use this (if you want a backup):

use strict;
use autodie;
use File::Copy;

my $file = "unix_url.txt";
open my $fh,  "<",  $file;
open my $tmp, ">", "$file.bak";
while (<$fh>) {
    s/\//\\/g;
    s/\\/c:/;
} continue { print $tmp $_ }
close $tmp;
close $fh;
move "$file.bak", $file;

Upvotes: 0

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