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

Hi, I think I'm trying to do something that's not possible... I am using Control::CLI to interact with remote servers. I have need in my script to watch a log file until certain lines are seen and react to them accordingly. I am trying to open the command with a pipe so I can read the output into my script, but it doesn't work. I've tried the only 2 things I can think of/find online, and both fail.

open(LOG, $NE_obj->cmd("tail -f /path/to/log |"));
open(LOG, '$NE_obj->cmd("tail -f /path/to/log")|');

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Any thoughts on how this could work? Is it even possible? Thanks in advance!

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Re: Open Control::CLI Command With Pipe
by crusty_collins (Friar) on Jun 02, 2017 at 15:10 UTC
    You can do this, I had the same issue last year. This is my solution. 
    sub waitForCmd {
        my $href        = shift(@_);

        return if ( not defined $href->{settings}->{nohup} );

        # wait for the file
        #
        sleep 1    while ( ! -e "$href->{settings}->{runfolder}/$href-
+>{settings}->{logfile}" );

        open( FH ,'<', "$href->{settings}->{runfolder}/$href->{setting
+s}->{logfile}" );

        # keep track of spinner
        #
        my @sails = map { "\b$_" } qw{- \ | /};
        my $sail = 0;

        # now search each line for job completed
        #
        FILE:
        for (;;) {
                while (<FH>) { 

                        print $sails[$sail++ % @sails] ;            

                        last FILE, if ( $_ =~  /Stopping AppMonitor Co
+nnector|
                                                Failure|
                                                Maximum return code ex
+ceeded for the run
                                                /xi );
                }
                seek(FH, 0, 1);
        }

        close (FH);
        return;
}

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    "We can't all be happy, we can't all be rich, we can't all be lucky – and it would be so much less fun if we were. There must be the dark background to show up the bright colours." Jean Rhys (1890-1979)
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Re: Open Control::CLI Command With Pipe
by ImJustAFriend (Scribe) on Jun 02, 2017 at 16:12 UTC

    Thanks for the feedback, crusty_collins! I've been poking around while waiting on a reply here. A little more careful reading of the Perl doc for open revealed my mistake. Here's the command that worked appropriately:

    open(LOG, "-|", $NE_obj->cmd("tail -f /path/to/log"));

    [download]
[reply]
[d/l]

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