Perl getpwnam fails in sub

Question

So i'm trying to use getpwnam() to search etc/passwd for a username in a sub, and return true if it exists. I keep getting the error "Use of uninitialized value in getpwnam".

sub nameSearch
{
$search = $_;
@name = getpwnam($search);
if ( ! defined $name[0])
{
return 0;
}
else
{
return 1;
}
}

I'm passing a chomped string into this sub. I've tried just using @name = getpwnam($_[0]) and @name = getpwnam($_)

I know as a fact that string i'm passing exists as a username in /etc/passwd and the code works when its not in a sub.

Can you show us how you're calling this `sub`, and how it compares to the inline version that purportedly works? Also, why aren't `$search` and `@name` local to the `sub`? ie. `my $search` and `my @name`? — Joe Z, Nov 16 '13 at 17:39
I'm a bit of a noob at Perl, didn't realize that was how local variables were called! Thanks for bringing it to my attention! — sh3rifme, Nov 25 '13 at 11:02

mpapec · Accepted Answer · 2013-11-16T18:19:38.280

If you're passing user name as a parameter then you should check first element of @_ which is $_[0].

$_ is global variable conveniently used as implicit foreach variable and function can use it in case no parameter was sent to it. Actually this is common behavior for most perl core functions which take $_ if no explicit argument is given.

sub nameSearch {
  my ($search) = @_;
  $search = $_ if !@_;

  my @name = getpwnam($search);

  return @name ? 1 : 0;
}

print nameSearch("user") ? "exist" : "doesn't exist";

Perl getpwnam fails in sub

1 Answers1