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

Hi, I have the below code. The array @ABC is basicly 50 lines of log information. I need to pass this into a open statement and have all 50 lines pass into the ticket program. When the code is executed as shown below, all that is outputted is "49". How do I get the real log information. 
open(RUN, "/usr/local/bin/ticket @ABC|");
       while($line = <RUN>) {
          print "$line";
       }
close(RUN);

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Thanks, Mike

Replies are listed 'Best First'.
Re: Passing an array into an open command
by tcf22 (Priest) on Mar 18, 2004 at 18:12 UTC
    It looks like it should work. I tried the following on Win32 Active Perl 5.8.

    test1.pl 
    my @a;
foreach(1..50){
    $a[$_-1] = $_;
}

open(T, "test2.pl @a|");
while(<T>){
    print;
}
close(T);

    [download]

    test2.pl 
    foreach(@ARGV){
    print "$_\n";
}

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    If I run test1.pl, I get 1..50 printed out on seperate lines, just like you would expect.

    UPDATE: Also works on Red Hat Linux 9. (Just change "test2.pl @a|" to "./test2.pl @a|" of course).

    - Tom

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      with passing @a to the script would you run into limits of a commandline if @a is say 10,000 elements, or does the exec not care? (it's been a long time since I've played with this)
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        Linux allows me to go up to around 23,000. Windows however crashed when i reach 530. I assume that there is some size or argument limit on most Oper. Systems.

        - Tom

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Re: Passing an array into an open command
by eXile (Priest) on Mar 18, 2004 at 20:19 UTC
    Mike, is the 'ticket' program expecting input from the command-line or on STDIN? If it is expecting input from STDIN and you want to process it's STDOUT, you can use IPC::Open2:

    test3.pl (emulates 'ticket' program') 
    #!/usr/bin/perl -w
use strict;
while (<STDIN>) {
        print "PROCESSED $_";
}

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    test4.pl 
    #!/usr/bin/perl -w
use strict;
$|++;
use IPC::Open2;

my @loglines=("This is not a relevant logline",
"This is not a relevant logline",
"This might be an interesting logine",
"Another interesting logline");

open2(*READ,*WRITE,"./test3.pl") or die;
foreach my $inputline (@loglines) {
        print WRITE "$inputline\n";
}
close (WRITE);

my $outputline;
while ($outputline = <READ>) {
        print $outputline;
}

    [download]
    As a sidestep: if you use 'open', please check if it succeeds, like: 
    open(RUN, "/usr/local/bin/ticket @ABC|") or die "useful error message 
+here";

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Re: Passing an array into an open command
by NovMonk (Chaplain) on Mar 18, 2004 at 18:13 UTC
    Shouldn't it be 

         while (<RUN>){
          print $line;
     }

    [download]

    ?

    If I'm completely missing the boat, I trust one of my brother/ sister monks will be gentle with their enlightenment....

    Good luck,

    NovMonk

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[d/l]
      I don't think so. the while (<RUN>) assigns the line from the RUN filehandle to $_, then you print out $line (which hasn't been assigned anything in this snippet). I don't think that's what the OP wants.
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[d/l]
[select]
        Ah. I see.

        I was trying to identify that what he wanted to do was run through his <RUN> and print something-- I just used his $line variable without thinking about what that does.

        Oh well. At least I knew his  while ($line= <RUN>... was a problem. I may get the hang of this yet. Thanks for the feedback.

        pax,

        NovMonk

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Re: Passing an array into an open command
by Roy Johnson (Monsignor) on Mar 18, 2004 at 20:04 UTC
    Any chance you've got newlines in your @ABC data? Have you printed out what the command line you assemble looks like? What does the output of 49 from the ticket program indicate?
    The PerlMonk tr/// Advocate
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Re: Passing an array into an open command
by amw1 (Friar) on Mar 18, 2004 at 18:10 UTC
    Here's how I'd do it. 
    #populate @ABC for pourposes of the test
@ABC = qw[ticket1 ticket2 ticket3];

foreach my $ticket (@ABC)
{
   my $line = qx{/usr/local/bin/ticket $ticket};

   # print qx{.... would also accomplish this
   # assuming you want to do more to $line than print
   print $line;
}

    [download]
     nevermind, missed the fact that all args were needed at once. *sigh*
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[d/l]
Re: Passing an array into an open command
by ambrus (Abbot) on Mar 18, 2004 at 20:00 UTC

    You might try using the new "three-argument" form of the open func, but it will have more than three arguments here.

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