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