NAME
       pid - Retrieve process identifiers

SYNOPSIS
       pid ?fileId?


DESCRIPTION
       If  the  fileId  argument  is  given then it should normally refer to a
       process pipeline created with the open command.  In this case  the  pid
       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  fileId refers to an open file that isn't a process pipeline.  If no
       fileId argument is given then pid returns the process identifier of the
       current  process.   All  process  identifiers  are  returned as decimal
       strings.

EXAMPLE
       Print process information about the processes in a pipeline  using  the
       SysV ps program before reading the output of that pipeline:

              set pipeline [open "| zcat somefile.gz | grep foobar | sort -u"]
              # Print process information
              exec ps -fp [pid $pipeline] >@stdout
              # Print a separator and then the output of the pipeline
              puts [string repeat - 70]
              puts [read $pipeline]
              close $pipeline


SEE ALSO
       exec(n), open(n)


KEYWORDS
