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I am trying to determine the PID when opening of a file handle from within
my main perl code. Here is a snip where i call the open file handle.

$infile = 'infile';
open(IF, "tail -f $infile|") or die "Cannot open pipe $infile\n";

while (<IF>) {
do_smothing()
}

In the example below in unix the main perl code has a pid of perl variable
$$ (PID=18629) then the open file handle has another PID, a child of the
parent (PID = 18630)

% ps -ef| grep tail
user 18632 18455 0 10:42:06 pts/10 0:00 grep tail
user 18630 18629 0 10:42:02 pts/10 0:00 tail -f infile
% ps -ef| grep myscript.pl
user 18634 18455 0 10:42:12 pts/10 0:00 grep myscript.pl
user 18629 18455 0 10:42:02 pts/10 0:00 /usr/bin/perl ./myscript.pl

Is there a way within perl to get the child PID 18630 ?

Thanks in advance.
Joey

On 15 Jul 2003 07:47:14 -0700
(Joey) wrote:
>
> I am trying to determine the PID when opening of a file handle from within
> my main perl code. Here is a snip where i call the open file handle.
>
> $infile = 'infile';
> open(IF, "tail -f $infile|") or die "Cannot open pipe $infile\n";
>
> while (<IF>) {
> do_smothing()
> }
>
> In the example below in unix the main perl code has a pid of perl variable
> $$ (PID=18629) then the open file handle has another PID, a child of the
> parent (PID = 18630)
>
> % ps -ef| grep tail
> user 18632 18455 0 10:42:06 pts/10 0:00 grep tail
> user 18630 18629 0 10:42:02 pts/10 0:00 tail -f infile
> % ps -ef| grep myscript.pl
> user 18634 18455 0 10:42:12 pts/10 0:00 grep myscript.pl
> user 18629 18455 0 10:42:02 pts/10 0:00 /usr/bin/perl ./myscript.pl
>
> Is there a way within perl to get the child PID 18630 ?
>
> Thanks in advance.
> Joey

open() should do that for you. it's in "perldoc -f open",
the bit where it says: "If the `open' involved a pipe, the
return value happens to be the pid of the subprocess."

which is nice.




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On 15 Jul 2003, Joey wrote:

>I am trying to determine the PID when opening of a file handle from within
>my main perl code. Here is a snip where i call the open file handle.
>
>$infile = 'infile';
>open(IF, "tail -f $infile|") or die "Cannot open pipe $infile\n";

When open() is doing more than just opening a file (that is, when you're
piping), it returns not only success or failure, but the actual PID.

my $pid = open(TAIL, "tail -f $infile |")
or die "cannot `tail -f $infile`: $!";

--
Jeff Pinyan RPI Acacia Brother #734 2003 Rush Chairman
"And I vos head of Gestapo for ten | Michael Palin (as Heinrich Bimmler)
years. Ah! Five years! Nein! No! | in: The North Minehead Bye-Election
Oh. Was NOT head of Gestapo AT ALL!" | (Monty Python's Flying Circus)