Dean Do wrote:
>
> Hello,
Hello,
> I'm rather new to PERL. How do I go about sorting
> a simple text file using PERL? This is what I want
> to accomplish.
>
> # sort /etc/passwd > /etc/passwd-new
> # mv /etc/passwd-new /etc/passwd
Are you sure you want to modify /etc/passwd? Which field do you want to sort on?
#!/usr/bin/perl
# *** UNTESTED ***
use warnings;
use strict;
use Fcntl qw( :flock :seek );
my $file = '/etc/passwd';
open my $fh, '+<', $file or die "Cannot open $file: $!";
flock $fh, LOCK_EX or die "Cannot lock $file: $!";
# sort on the user name field
my @records = map $_->[ 1 ],
sort { $a->[ 0 ] cmp $b->[ 0 ] }
map [ (split /:/)[ 0 ], $_ ],
<$fh>;
# sort on the UID field
#my @records = map $_->[ 1 ],
# sort { $a->[ 0 ] <=> $b->[ 0 ] }
# map [ (split /:/)[ 2 ], $_ ],
# <$fh>;
seek $fh, 0, SEEK_SET or die "Cannot seek on $file: $!";
# you could also use truncate() here but since you are not
# changing the size of the data it is not necessary.
print $fh @records or die "Cannot print to $file: $!";
# close and unlock the file
close $fh;
__END__
If you are going to try this out, MAKE A BACKUP COPY of the file first!
If you screw up the /etc/passwd file without a backup you are going to
be in a world of hurt.
John
--
use Perl;
program
fulfillment
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