Program unsuspectingly dies with no reason why. -FIXED!

misconfiguration has asked for the wisdom of the Perl Monks concerning the following question:

Statement to do something if <> calls $remove.

if ($remove) {
    $remove = lc($remove);
    my $removeq = $remove;
    my %remove_cmd = ( remove => "rmquedev -d $removeq -q $removeq" );
    print "Are you sure you want to remove print queue \"$removeq\" [Y
+/n]?";
    $_ = <>;
    chomp($_);
    $_ = "Y" if ( length($_) == 0 );
    if ( $_ =~ /[Yy]/ ) {

        # Wait for user-input

        system( $remove_cmd {'remove'} );
        print
"Prepairing to remove \"$removeq\" from the CC_print.printers file.\n"
+;
        sleep 2;
        &clean_the_file();
        }
        else {
            die "You chose NOT to remove queue \"$removeq\"\n";
        }
    }
[download]

Sub-process being called

sub clean_the_file {
    my $sourcefile = "/u/ccsys/CC_print.printers";

    # Keep a dedicated backup of CC_print.printers
    if ( !-t "/root/CC_print.printers.bkp" ) {
        system("touch /root/CC_print.printers.bkp");
        system("cp -R $sourcefile /root/CC_print.printer.bkp");
    }
    if ( -t "/root/CC_print.printers.bkp" ) {
        system("cp -R $sourcefile /root/CC_print.printer.bkp");

# grab the sourcefile and the string to remove as the first and second
+ arguments
        my ( $sourcefile, $removeq ) = @_;

        # create a temporary file
        system("touch /u/ccsys/CC_print.printers.bkp_mkpq");
        my $tempfile = "/u/ccsys/CC_print.printers.bkp_mkpq";

      # extract lines from $sourcefile which do NOT have the string to
+ remove
      # note that the \' inserts ticks so that strings with spaces can
+ work, too
        `grep -v $removeq $sourcefile > $tempfile`;
        sleep 1;
        print "Waiting to unlink..\n";

        # delete source file, then rename working file
        unlink($sourcefile);
        rename( $tempfile, $sourcefile );
        system("rm -rf $tempfile");
    }
}
[download]

Program is dying as the sub(); is being called with nothing telling me why!

I'm using Strict and Warnings, could anyone offer some insight?

UPDATE!!
The data I was trying to parse looks like this
#CC:'queue-01':ps|2|-5|1.0|1.0:tp'
#CC:'queue-02':ps|2|-5|1.0|1.0:tp'
#CC:'queue-03':ps|2|-5|1.0|1.0:tp'
#CC:'queue-04':ps|2|-5|1.0|1.0:tp'
#CC:'queue-05':ps|2|-5|1.0|1.0:tp'
#CC:'queue-06':ps|2|-5|1.0|1.0:tp'
#CC:'queue-07':ps|2|-5|1.0|1.0:tp'
#CC:'queue-08':ps|2|-5|1.0|1.0:tp'
#CC:'queue-09':ps|2|-5|1.0|1.0:tp'

I have changed my code and now I can execute which printer needs to be deleted from the file successfully, while maintaining a dedicated backup of the file before it was changed :).

 
sub cleanthefile {
    my @filehandles;

    # Keep varibles in same order as they were passed to the sub-routi
+ne

    my ( $removeq, $sourcefile, $tempfile, $backup ) = @_;

    # Keep a dedicated backup of CC_print.printers
    if (-e "$_[3]" ) {
        system ( "cp -R $_[1] $_[3]" );

        # create a temporary file
        if ( !-e  "$_[1]") {
        system("touch $_[2]");
        }

      # extract lines from $sourcefile which do NOT have the string to
+ remove
      # note that the \' inserts ticks so that strings with spaces can
+ work, too
        if ( -e "$_[1]") {
        # system ("cat $sourcefile \| grep -v $removeq $sourcefile > $
+tempfile");
        system ( "grep -v $_[0] $_[1] > $_[2]" );
        sleep 1;
        print "Waiting to unlink..\n";

        # delete source file, then rename working file
        unlink($_[1]);
        rename( $_[2], $_[1] );
        system("rm -rf $_[2]");

    }
}
    else {
        system("touch $_[3]");
        system("cp -R $_[1] $_[3]");
    }
}
[download]

Command that was run
mkpq -r queue-03
[download]

As you can see, the queue-03 is gone!
#CC:'queue-01':ps|2|-5|1.0|1.0:tp'
#CC:'queue-02':ps|2|-5|1.0|1.0:tp'
#CC:'queue-04':ps|2|-5|1.0|1.0:tp'
#CC:'queue-05':ps|2|-5|1.0|1.0:tp'
#CC:'queue-06':ps|2|-5|1.0|1.0:tp'
#CC:'queue-07':ps|2|-5|1.0|1.0:tp'
#CC:'queue-08':ps|2|-5|1.0|1.0:tp'
#CC:'queue-09':ps|2|-5|1.0|1.0:tp'

Thanks again everyone!

Comment on Program unsuspectingly dies with no reason why. -FIXED! Select or Download Code

Replies are listed 'Best First'.
Re: Program unsuspectingly dies with no reason why. by kyle (Abbot) on Feb 13, 2008 at 20:56 UTC
Here are the relevant lines: &clean_the_file(); sub clean_the_file { my ( $sourcefile, $removeq ) = @_; `grep -v $removeq $sourcefile > $tempfile`; } [download] You're calling `clean_the_file` with no arguments, and passing those (no) arguments on to grep, which is going to hang waiting for input. That's my guess.	[reply] [d/l] [select]
Re^2: Program unsuspectingly dies with no reason why. by misconfiguration (Sexton) on Feb 13, 2008 at 21:21 UTC
I think I'm going to have to agree with Kyle. Does anyone think I should remove the grep -v function from backticks and have Perl handle it with the system(); call? I think I'm going to try it this way, so far not much luck with the issue. Thanks for all of the replies so far!	[reply]
Re^3: Program unsuspectingly dies with no reason why. by kyle (Abbot) on Feb 13, 2008 at 21:41 UTC
Backticks are for when you want to capture the output of some shell command. In this case, you're redirecting output to a file, so backticks won't do that. Your backticks also don't give you anything in a void context. That said, putting the same thing in system won't help either. It's the underlying `grep` that's hanging. I think that grep needs to get some arguments. You could do this, minimally: `grep -v $removeq $sourcefile /dev/null /dev/null > $tempfile`; [download] That won't hang, but it also won't work until `$removeq` and `$sourcefile` are right. You probably ought to be passing them in initially: `&clean_the_file( $sourcefile, $removeq );` [download] I can't tell what `$sourcefile` should be, though. Hope this helps.	[reply] [d/l] [select]
Re^4: Program unsuspectingly dies with no reason why. by misconfiguration (Sexton) on Feb 14, 2008 at 15:20 UTC
Re^5: Program unsuspectingly dies with no reason why. by kyle (Abbot) on Feb 14, 2008 at 18:59 UTC
Some notes below your chosen depth have not been shown here
Re^3: Program unsuspectingly dies with no reason why. by toolic (Bishop) on Feb 13, 2008 at 21:35 UTC
I think you missed Kyle's point. Using `system` instead of backticks to call grep should not matter here. To illustrate Kyle's point, add these lines just before your grep line: `print "removeq = $removeq\n"; print "sourcefile = $sourcefile\n";` [download] I suspect these variables will not contain what you expect them to.	[reply] [d/l] [select]
Re: Program unsuspectingly dies with no reason why. by starX (Chaplain) on Feb 13, 2008 at 20:41 UTC
It might have something to do with the line `&clean_the_file();` The `&` denotes a function reference, but you're not calling the function via a reference. If you use `clean_the_file();` I think it'll take care of the issue. Update: Never mind, I'm a loser. --starX www.axisoftime.com	[reply] [d/l] [select]
Re^2: Program unsuspectingly dies with no reason why. by Fletch (Bishop) on Feb 13, 2008 at 20:46 UTC
Errm, no. Something like `\&clean_the_file` would be a reference. While calling subs with the leading sigil does have an effect, it's not going to stop `&clean_the_file()` from being called in any sane circumstance. See perlsub. (Of course if someone has created just such a circumstance then they deserve what they get for using prototypes where they shouldn't :) The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l] [select]
Re^2: Program unsuspectingly dies with no reason why. by kyle (Abbot) on Feb 13, 2008 at 20:48 UTC
Actually, `&foo()` is a call to the sub `foo`. To take a reference to the sub, use `\&foo`. `sub foo { print "foo: ", $_[0], "\n" } &foo( 'called with &' ); foo( 'called with no &' ); my $foo_ref = \&foo; $foo_ref->( 'called via reference' ); &$foo_ref( 'called via & and reference' ); __END__ foo: called with & foo: called with no & foo: called via reference foo: called via & and reference` [download] The only special thing about `&foo()` vs. `foo()` is that the former will disable any prototypes the sub may have.	[reply] [d/l] [select]