.\" Hey Emacs! This file is -*- nroff -*- source.
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.\" Created for Debian using the original file "sig.announce.1.4"
.TH signal "3tcl" "1.4.0.1 Tcl" "Tcl Signal Extension"
.SH NAME
signal \- dynamically loadable signal handling for Tcl/Tk
.SH SYNOPSIS
\fBsignal\fI (add|delete|print|version) [options]
.SH "COMMANDS"
.SS add signo proc [\-async]
Adds a signal handler for signal signo through proc proc.
Signals can be provided by number, or the most common ones are provided by
name (e.g., SIGHUP).
The proc is any Tcl procedure, and it is evaluated when the signal comes in.
It will be provided no arguments.

Signal handlers have Posix semantics \- they persist until reset.

If 
.B \-async 
is used, the signal handler is created using 
.BR Tcl_AsyncCreate().
Checks for the signal are very frequent (each evaluation) using this
technique, but one doesn't know quite where evaluation is or how to handle
errors in this situation. The code will evaluate the provided procedure in 
the current interpreter if available, and in the interpreter which added the
signal handler otherwise. At least until a better scheme is suggested.

The 
.B \-async 
is especially useful to interrupt "runaway" procs, or to cause a
quick exit; the default mechanism simply waits for another MainLoop cycle.
.SS signal delete signo
Restores handling of signal signo to the default (
.B SIG_DFL
).
.SS signal print 
Prints the handling of all signals with handlers. Formatted as  
 signal ----> procedure or as
 signal !---> procedure 

if the signal is handled asynchronously
.SS signal print signo
Prints the procedure for handling signal signo.
Prints the word 
.B UNHANDLED 
if no signal handler is active for that signal.
.SS signal version
Returns the string representing the current version of the package
.SH AUTHOR
Michael Schwartz <mschwart@nyx.net>. Tilman Kranz <tilde@tk-sls.de> patched
this for wider portability on Linux