'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: pid.n,v 1.9 2007/12/13 15:22:33 dgp Exp $
'\" 
.so man.macros
.TH pid n 7.0 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
pid \- Retrieve process identifiers
.SH SYNOPSIS
\fBpid \fR?\fIfileId\fR?
.BE

.SH DESCRIPTION
.PP
If the \fIfileId\fR argument is given then it should normally
refer to a process pipeline created with the \fBopen\fR command.
In this case the \fBpid\fR command will return a list whose elements
are the process identifiers of all the processes in the pipeline,
in order.
The list will be empty if \fIfileId\fR refers to an open file
that is not a process pipeline.
If no \fIfileId\fR argument is given then \fBpid\fR returns the process
identifier of the current process.
All process identifiers are returned as decimal strings.
.SH EXAMPLE
Print process information about the processes in a pipeline using the
SysV \fBps\fR program before reading the output of that pipeline:
.PP
.CS
set pipeline [open "| zcat somefile.gz | grep foobar | sort -u"]
# Print process information
exec ps -fp [\fBpid\fR $pipeline] >@stdout
# Print a separator and then the output of the pipeline
puts [string repeat - 70]
puts [read $pipeline]
close $pipeline
.CE

.SH "SEE ALSO"
exec(n), open(n)

.SH KEYWORDS
file, pipeline, process identifier