while loop break when sub call

[papillon]

Hello,

I'm calling a sub inside a while loop and it break the $_ from getgrent. I tried to used local($_) before calling the sub but to no avail.

while( (my $name,$passwd,$gid,$members) = getgrent() ){
   if ( $name =~ m/^sometext_(\w+)/ ) {
        local($_);
        my $var = sub($name, $1);
        print ($name."\n");
   }
}

the while loop execute correctly until it reach a $name that start with sometext_. At that point, the while loop just repeat the over the same group and never exit.

Is there a way to let getgrent continue where it was?

Thanks,

Mélanie

[kennethk]

The thread to date sounds like you are not posting enough information, and that you've scrubbed your example too much to effectively debug. Please read How do I post a question effectively?, in particular, make sure that you post self-contained code that shows the problem. What happens in the subroutine? Nothing that's been posted should be resetting the getgrent iterator, though if you invoke it in your subroutine, that could mess you up. Note that the one-liner

perl -E 'sub func {"@_"} while (($name) = getgrent){if ($name =~ /^som
+etext_(\w+)/){func($name,$1);say $name}}';

runs just as I would expect, with no infinite loop.

[papillon]

Your comment pointed my mistake. In the subroutine, I create a new group, that must be the source of the problem.

Using an intermediate array solved the problem. One of those cause that is so evident that you don't see it

[sundialsvc4]

Yes, undoubtedly the creation of a new group broke the iterator.   That sort of thing happens a lot, and it goes back to the underlying operating system primitives.   For example, I’ve found that when iterating through files and directories in Microsoft Windows (regardless of language), you mustn’t create/remove files or directories while doing so.   First complete the scan (e.g. of one complete subdirectory), then act upon/iterate through an in-memory list of the things that the scan finds, and all is well.

[toolic]

Update your post using "code" tags around your Perl code: Writeup Formatting Tips

Your code does not compile for me. I get this error:

Illegal declaration of anonymous subroutine at ...

and with diagnostics:

Illegal declaration of anonymous subroutine at ... (#2)
    (F) When using the sub keyword to construct an anonymous subroutin
+e,
    you must always specify a block of code. See perlsub.

There are other errors if you use strict.

[sundialsvc4]

You really need to post the code within <code> tags as described in Markup in the Monastery at the bottom of the submit-page.

If you suspect that someting in sub() might be adversely affecting repeated calls to getgrent(), consider defining an array and pushing all matching names onto it.   Then, after the getgrent loop has finished, use a second loop to process the entries in the array.   Similar side-effects can happen e.g. when processing files within a loop that is scanning directories, on some types of machines.   So, first do one, then the other.

[papillon]

Hello,

Sorry for forgetting the <code> tags.

I tried to fill an array for matching groups name and then iterating that array and it work

Thanks

[LanX]

Did you really name your function "sub"?

That's a bad idea, sub is a reserved word.

[papillon]

no, I did not do that mistake, it was just for the example. Should have named it to something else anyway