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

First, see ztk-visual-top-w-kill. In that app, one of my apps named "home/zentara/bin/claws" shows up as a name 3 in the output. I think this is a top bug, where for some reason I'm getting a scalar of an array for that name? Anyways, I would appreciate it if anyone could explain it. Below is a simplified version. Maybe it dosn't show on your machine? 
#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;

my $pid1 = open3(0, \*READ,\*ERR,"top -d 1 -b");

while(1){
  my @words = split(/\s+/,<READ>);
print "@words\n";
}

waitpid($pid, 1);

[download]
I'm not really a human, but I play one on earth. Cogito ergo sum a bum

Replies are listed 'Best First'.
Re: unexplained output from top in batch mode
by jettero (Monsignor) on Jan 13, 2007 at 12:57 UTC

    UPDATE: Would you mind restating, "'home/zentara/bin/claws' shows up as a name 3 in the output.?" I may not have answered anything relevent in the rest of this post.

    I don't think split /s\+/ is going to be very robust here. The columns have a certain width and the fields may have spaces in them... A ways back I had written a funny little toy that I seem to use over and over. Perhaps I should make it into a proper module.

    Read more... (2 kB)

    It'd work like so: 

    use magic_columator;

while(my @row = $col->fetchrow) {
   # do stuff
}

    [download]

    This would be a great place to use iterators I think. There are also probably already modules that do this more cleanly. If you were to use it, or something like it, it'd need some major updates and fixes I suspect.

    -Paul

[reply]
[d/l]
[select]
      Well, if you use the script in ztk-visual-top-w-kill, and go into the thread where I sysread top's output. and print the $buf, 
        sysread(READ,$buf,8192);  
   print "$buf\n\n";

      [download]
      you will see that top's batch output is setting the name to 3 (at least on my machine for /home/zentara/bin/claws), when it's still a string, before any split occurs.

      So the question is whether it is top's -b option that does this, or does the IPC::Open3 pipe somehow change it?

      When top is run in normal mode(like in an xterm), the name is shown correctly.

      Also if I do "top -b >>top.output", the name is shown correctly as "claws". So somehow, coming thru the IPC::OPen3 pipe is causing it to change. Is it possible that a pipe is interpreted to be a weird terminal type (not vt100)?

      I'm not really a human, but I play one on earth. Cogito ergo sum a bum
[reply]
[d/l]

        K, then I stand by my previous guess. Sometimes columns can have embedded spaces (like the leading spaces on RES and SHR, etc), and I think that might be messing up your column numbers. If it's just the one process getting renamed, I'd look for something stranger going on, but somehow I think it's going to relate to split /\s+/

        -Paul

[reply]
[d/l]

Back to Seekers of Perl Wisdom