Interesting. An Expect-like approach had not occurred to me, but it sounds like it would be a good way to attack a program like top that is *usually* interactive (though I was hoping to side-step all the terminal-ish issues w/ the -b flag of top.
<sigh>

Thanks,
./ddd

I don't know the answer to your question, but I noticed a bad practice. When including Perl source code that's not in a package, you should use do "filename.pl", not require "filename.pl", because it will fail in this scenerario:

package AAA;
require "111.pl";
longestLineLength(@a);  # Works.
package BBB;
require "111.pl";       # Does nothing. Already required.
longestLineLength(@a);  # ERROR.

-vs-

package AAA;
do "111.pl";            # Creates &AAA::longestLineLength
longestLineLength(@a);  # Works.
package BBB;
do "111.pl";            # Creates &BBB::longestLineLength
longestLineLength(@a);  # Works.
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Of course, it wouldn't hurt to put the extra line to make it into a module that you could require/use.

Good point, the require is something that I used just for the demo app. (I haven't put a require in my *real* code since Perl4 days ;-)

(Sorry, wasn't logged in)

FWIW, I get good results with backticks. For example:

% perl -MList::Util=max -lwe '
print max map length, `COLUMNS=1000 top -bcS -n 1 2>err.txt`'
208
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My system is Debian Linux, and

% top --version
top (procps version 2.0.7)
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Damn, backticks didn't occur to me. (somehow I've gotten in the habit of always using open(H, "app |")). I'll try this out as soon as I get back in the office tomorrow - will let you know.

Thanks!
./ddd

Actually, it's not a backtick thing; that was just the first thing I tried; when I run your code I also get the desired results. Specifically:

# lll.pl
sub longestLineLength {
  my $longestLen = undef;
  for my $l ( @_ ) {
    if ( length($l) > $longestLen ) {
      $longestLen = length($l);
    }
  }
  return $longestLen;
}

1;  # propitiatory offering for require
__END__

# test03.pl
use strict;
use warnings;

require "lll.pl";

open (TOP, "COLUMNS=1000 /usr/bin/top -bcS -n 1 2>err.txt|")
  || die "open pipe from top failed $!";
print longestLineLength( <TOP> ) . "\n";
__END__
% perl test03.pl
208
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the lowliest monk

Nope. Same behavior with backticks.
Darn.

And then implement pacct for the process history.

Cricket looks great! Once I get it up and running on our build box, I'll see about adding it to our customer installs!

Many Thanks!
./ddd

while (<STDIN>) {                   # reads from STDIN
    unless (/\d/) {
        warn "No digit found.\n";   # writes to STDERR
    }
    print "Read: ", $_;             # writes to STDOUT
}
END { close(STDOUT)                 or die "couldn't close STDOUT: $!"
+ }
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#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;
use IO::Select;

my $pid = $$;

my $pid1 = open3(0, \*READ,\*ERROR,"top -d 1 -b -p $pid ");
#if \*ERROR is false, STDERR is sent to STDOUT 

my $sel = new IO::Select();

$sel->add(\*READ);
$sel->add(\*ERROR);

while(1){

foreach my $h ($sel->can_read){
    my $buf = '';
        if ($h eq \*ERROR){
              sysread(ERROR,$buf,4096);
              if($buf){print "ERROR-> $buf\n"}
}else{

 sysread(READ,$buf,4096);
    if($buf){print "$buf\n"}
   }
  }
}
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Nope, still 80 cols (even after adding $ENV{'COLUMNS'} = 1000;).

Neat tho', Both IPC::Open3, and IO::Select are new to me.

./ddd

If you are looking to fool the process into different columns, maybe you need to use IO::Pty. I havn't been able to figure it out myself, but there is something in "clone_winsize_from(\*FH)".

I have this example in my collection, and I can't remember where I got it...probably google.groups or here. Anyway, it may have a few hints for you.

#!/usr/bin/perl -w
# Description: Fool a process into 
# thinking that STDOUT is a terminal, when in fact 
# it may be a file or a pipe. This can be useful 
# with programs like ps and w on linux... which 
# will trunc their output to the width of the 
# terminal, and, if they cannot detect the terminal 
# width, use a default 80 columns. Wouldn't it be 
# nice to say "ps -aux | grep etcshadow", and get 
# output that looks like when you just say "ps 
# -aux"? Well, that's the idea. 

#try ./pseudotty "xterm -e top" 
#or  ./pseudotty top 

use warnings;
use strict;
use IO::Pty;

die "usage: ptyexec command [args]\n" unless @ARGV;

my $pty = IO::Pty->new;
my $slave = $pty->slave;
open TTY,"/dev/tty" or die "not connected to a terminal\n";
$pty->clone_winsize_from(\*TTY);
close TTY;

my $pid = fork(); die "bad fork: $!\n" unless defined $pid;
if (!$pid) {
#  $slave->close(); 
  open STDOUT,">&=".$pty->fileno() or die $!;
  exec @ARGV;
}else{
  $pty->close();
     while (defined (my $line = <$slave>)) {
       print $line;
     }
}

#cleanup pty for next run 
$pty->close();
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---

I'm not really a human, but I play one on earth. flash japh