Vahid Moghaddasi wrote:
Hi,
Hello,
I have a very strange problem (to me anyways). I have the following
subroutine to sort unique a UNIX password file based on UID and
username. But the problem is that some of the users get disappeared
the output password file. I couldn't figure out the pattern of user
disappearance but always the same few users are filtering.
Can someone please take a look at my code and tell me why is it
messing with me?
In the Unix password file format the user name has to be unique however
the UID need not be so it is possible that two or more users have the
same UID.
Any suggestion to rewrite it is also welcome. Thank
you all.
sub Sort {
my ($infile,$outfile) = @_;
my @unique = ();
my %seen = ();
my() creates lexical variables that are already empty by default so
assigning nothing to them is pointless.
open my $tmp_out, '>', "$outfile"
or die "could not write the sorted list: $!";
open my $tmp_in, '<', "$infile"
or die "could not open $infile to sort: $!";
perldoc -q quoting
Found in /usr/share/perl/5.8/pod/perlfaq4.pod
What’s wrong with always quoting "$vars"?
while (<$tmp_in>) {
next if (m/^#/); # Skip comments
next if (m/^\s*$/); # Skip blank lines
my $uname = (split /:/)[0]; # username
my $uid = (split /:/)[2]; # uid
Instead of split()ting twice you can extract both fields with one split():
my ( $uname, $uid ) = ( split /:/ )[ 0, 2 ];
next if $seen{ $uid }++;
next if $seen{ $uname }++;
push @unique, $_;
}
print $tmp_out @unique;
print "DEBUG: Finishing Sort function.\n" if $DEBUG;
}
If you are reading from *the* /etc/passwd file then you could use perl's
built-in getpwent()/setpwent()/endpwent()/getpwnam()/getpwuid() functions.
John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall
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