NAME

       pid - Retrieve process identifiers

SYNOPSIS

       pid ?fileId?
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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 is not 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(3tcl), open(3tcl)

KEYWORDS

       file, pipeline, process identifier