tcl::process - Subprocess management

       This  command  provides a way to manage subprocesses created by the open and exec commands, as identified
       by the process identifiers (PIDs) of those subprocesses. The legal options  (which  may  be  abbreviated)
       are:

       ::tcl::processautopurge ?flag?
              Automatic  purge facility. If flag is specified as a boolean value then it activates or deactivate
              autopurge. In all cases it returns the current status  as  a  boolean  value.  When  autopurge  is
              active,  Tcl_ReapDetachedProcs  is called each time the exec command is executed or a pipe channel
              created by open is closed. When  autopurge  is  inactive,  ::tcl::process  purge  must  be  called
              explicitly. By default autopurge is active.

       ::tcl::processlist
              Returns  the  list  of subprocess PIDs. This includes all currently executing subprocesses and all
              terminated subprocesses that have not yet had their corresponding process table entries purged.

       ::tcl::processpurge ?pids?
              Cleans up all data associated with terminated subprocesses. If pids is specified as a list of PIDs
              then the command only cleanup data for the matching subprocesses if  they  exist,  and  raises  an
              error otherwise. If a process listed is still active, this command does nothing to that process.

       ::tcl::processstatus ?switches? ?pids?
              Returns a dictionary mapping subprocess PIDs to their respective status. If pids is specified as a
              list  of PIDs then the command only returns the status of the matching subprocesses if they exist,
              and raises an error otherwise. For active processes, the status is an empty value. For  terminated
              processes, the status is a list with the following format: “{code ?msgerrorCode?}”, where:

              code   is a standard Tcl return code, i.e., 0 for TCL_OK and 1 for TCL_ERROR,

              msg    is the human-readable error message,

              errorCode
                     uses the same format as the errorCode global variable

              Note that msg and errorCode are only present for abnormally terminated processes (i.e. those where
              the  code is nonzero). Under the hood this command calls Tcl_WaitPid with the WNOHANG flag set for
              non-blocking behavior, unless the -wait switch is set (see below).

              Additionally, ::tcl::processstatus accepts the following switches:

              -wait  By default the command returns immediately (the underlying Tcl_WaitPid is called  with  the
                     WNOHANG  flag  set)  unless this switch is set. If pids is specified as a list of PIDs then
                     the command waits until the status of the matching subprocesses are available. If pids  was
                     not specified, this command will wait for all known subprocesses.

              --     Marks  the  end  of switches.  The argument following this one will be treated as the first
                     arg even if it starts with a -.

       These show the use of ::tcl::process. Some of the results  from  ::tcl::processstatus  are  split  over
       multiple lines for readability.

              ::tcl::processautopurge→true::tcl::processautopurge false
                   →false

              set pid1 [exec command1 a b c | command2 d e f &]
                   →123456
              set chan [open "|command1 a b c | command2 d e f"]
                   →file123
              set pid2 [pid $chan]
                   →7891011::tcl::processlist→1234567891011::tcl::processstatus→1230456{1"childkilled:writeonpipewithnoreaders"{CHILDKILLED456SIGPIPE"writeonpipewithnoreaders"}}789{1"childsuspended:backgroundttyread"{CHILDSUSP789SIGTTIN"backgroundttyread"}}1011{}::tcl::processstatus 123
                   →1230::tcl::processstatus 1011
                   →1011{}::tcl::processstatus -wait
                   →1230456{1"childkilled:writeonpipewithnoreaders"{CHILDKILLED456SIGPIPE"writeonpipewithnoreaders"}}789{1"childsuspended:backgroundttyread"{CHILDSUSP789SIGTTIN"backgroundttyread"}}1011{1"childprocessexitedabnormally"{CHILDSTATUS1011-1}}::tcl::processstatus 1011
                   →1011{1"childprocessexitedabnormally"{CHILDSTATUS1011-1}}::tcl::processpurge
              exec command1 1 2 3 &
                   →1213::tcl::processlist→1213

       background, child, detach, process, wait

Tcl                                                    9.0                                         process(3tcl)

       tcl::process - Subprocess management

exec(3tcl), open(3tcl), pid(3tcl), Tcl_DetachPids(3tcl), Tcl_WaitPid(3tcl), Tcl_ReapDetachedProcs(3tcl)

::tcl::processoption ?argarg...?
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