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Passing an array into an open command

by mikeysmailbox (Initiate)
on Mar 18, 2004 at 18:01 UTC ( #337747=perlquestion: print w/replies, xml ) Need Help??

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);
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.
    my @a; foreach(1..50){ $a[$_-1] = $_; } open(T, " @a|"); while(<T>){ print; } close(T);
    foreach(@ARGV){ print "$_\n"; }
    If I run, I get 1..50 printed out on seperate lines, just like you would expect.

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

    - Tom

      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)
        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

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: (emulates 'ticket' program')
    #!/usr/bin/perl -w use strict; while (<STDIN>) { print "PROCESSED $_"; }
    #!/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,"./") or die; foreach my $inputline (@loglines) { print WRITE "$inputline\n"; } close (WRITE); my $outputline; while ($outputline = <READ>) { print $outputline; }
    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";
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; }


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

    Good luck,


      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.
        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.



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
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; }
    nevermind, missed the fact that all args were needed at once. *sigh*
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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