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'\"
'\" Copyright (c) 2017 Frederic Bonnet.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH process n 8.7 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note: do not modify the .SH NAME line immediately below!
.SH NAME
tcl::process \- Subprocess management
.SH SYNOPSIS
\fB::tcl::process \fIoption \fR?\fIarg arg ...\fR?
.BE
.SH DESCRIPTION
.PP
This command provides a way to manage subprocesses created by the \fBopen\fR
and \fBexec\fR commands. The legal \fIoptions\fR (which may be abbreviated) are:
.TP
\fB::tcl::process list\fR
.
Returns the list of subprocess PIDs.
.TP
\fB::tcl::process status\fR ?\fIswitches\fR? ?\fIpids\fR?
.
Returns a dictionary mapping subprocess PIDs to their respective status. If
\fIpids\fR 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:
.QW "{code ?\fImsg errorCode\fR?}" ,
where:
.RS
.TP
\fBcode\fR\0
.
is a standard Tcl return code,
.TP
\fBmsg\fR\0
.
is the human-readable error message,
.TP
\fBerrorCode\fR\0
.
uses the same format as the \fBerrorCode\fR global variable
.RE
Note that \fBmsg\fR and \fBerrorCode\fR are only present for abnormally
terminated processes (i.e. those where \fBcode\fR is nonzero). Under the hood
this command calls \fBTcl_WaitPid\fR with the \fBWNOHANG\fR flag set for
non-blocking behavior, unless the \fB\-wait\fR switch is set (see below).
.RS
.PP
Additionally, \fB::tcl::process status\fR accepts the following switches:
.TP
\fB\-wait\fR\0
.
By default the command returns immediately (the underlying \fBTcl_WaitPid\fR is
called with the \fBWNOHANG\fR flag set) unless this switch is set. If \fBpids\fR
is specified as a list of PIDs then the command waits until the status of the
matching subprocesses are available. If \fBpids\fR is not specified then it
waits for all known subprocesses.
.TP
\fB\-\|\-\fR
.
Marks the end of switches. The argument following this one will
be treated as the first \fIarg\fR even if it starts with a \fB\-\fR.
.RE
.TP
\fB::tcl::process purge ?\fIpids\fR?
.
Cleans up all data associated with terminated subprocesses. If \fBpids\fR 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 the process is
still active then it does nothing.
.TP
\fB::tcl::process autopurge ?\fIflag\fR?
.
Automatic purge facility. If \fBflag\fR 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, \fBTcl_ReapDetachedProcs\fR is called
each time the exec command is executed or a pipe channel created by open is
closed. When autopurge is inactive, \fB::tcl::process\fR purge must be called
explicitly. By default autopurge is active.
.RE
.SH "EXAMPLES"
.PP
.CS
\fB::tcl::process autopurge\fR
\fI\(-> true\fR
\fB::tcl::process autopurge\fR false
\fI\(-> false\fR
set pid1 [exec command1 a b c | command2 d e f &]
\fI\(-> 123 456\fR
set chan [open "|command1 a b c | command2 d e f"]
\fI\(-> file123\fR
set pid2 [pid $chan]
\fI\(-> 789 1011\fR
\fB::tcl::process list\fR
\fI\(-> 123 456 789 1011\fR
\fB::tcl::process status\fR
\fI\(-> 123 0 456 {1 "child killed: write on pipe with no readers" {CHILDKILLED 456 SIGPIPE "write on pipe with no readers"}} 789 {1 "child suspended: background tty read" {CHILDSUSP 789 SIGTTIN "background tty read"}} 1011 {}\fR
\fB::tcl::process status\fR 123
\fI\(-> 123 0\fR
\fB::tcl::process status\fR 1011
\fI\(-> 1011 {}\fR
\fB::tcl::process status\fR -wait
\fI\(-> 123 0 456 {1 "child killed: write on pipe with no readers" {CHILDKILLED 456 SIGPIPE "write on pipe with no readers"}} 789 {1 "child suspended: background tty read" {CHILDSUSP 789 SIGTTIN "background tty read"}} 1011 {1 "child process exited abnormally" {CHILDSTATUS 1011 -1}}\fR
\fB::tcl::process status\fR 1011
\fI\(-> 1011 {1 "child process exited abnormally" {CHILDSTATUS 1011 -1}}\fR
\fB::tcl::process purge\fR
exec command1 1 2 3 &
\fI\(-> 1213\fR
\fB::tcl::process list\fR
\fI\(-> 1213\fR
.CE
.SH "SEE ALSO"
exec(n), open(n), Tcl_DetachPids(3), Tcl_WaitPid(3), Tcl_ReapDetachedProcs(3)
.SH "KEYWORDS"
background, child, detach, process, wait
'\" Local Variables:
'\" mode: nroff
'\" End:
|
