ssignal, gsignal

Purpose

     Implements a software signal facility.

Library

     Standard C Library (libc.a)

Syntax

     #include <signal.h>

     int (*ssignal (sig, action)) ( )          int gsignal (sig)
     int sig, (*action) ( );                   int sig;
     Description

     The ssignal and gsignal  subroutines implement a software
     facility similar  to that of  the signal and  kill system
     calls.  However,  there is no connection  between the two
     facilities.  User programs can use ssignal and gsignal to
     handle  exceptional  processing  within  an  application.
     signal  and related  system  calls handle  system-defined
     exceptions.

     The software signals available  are associated with inte-
     gers  in  the  range  1 through  15.   Other  values  are
     reserved for use by the C library and should not be used.

     The ssignal subroutine associates the procedure specified
     by the  action parameter with the  software signal speci-
     fied  by  the  sig  parameter.   The  gsignal  subroutine
     "raises" the signal sig,  causing the procedure specified
     by the action parameter to be taken.

     The  action parameter  is  either a  pointer  to a  user-
     defined  subroutine,  or  one of  the  constants  SIG_DFL
     (default  action)  and   SIG_IGN  (ignore  signal).   The
     ssignal subroutine returns the  procedure that was previ-
     ously established  for that signal.  If  no procedure was
     established before,  or if the signal  number is illegal,
     then ssignal returns the value SIG_DFL.

     The gsignal  subroutine "raises" the signal  specified by
     the sig parameter by doing the following:

     o   If the procedure for sig is SIG_DFL, then the gsignal
         subroutine returns  a value of  0 and takes  no other
         action.

     o   If the procedure for sig is SIG_IGN, then the gsignal
         subroutine returns  a value of  1 and takes  no other
         action.

     o   If the  procedure for sig  is a subroutine,  then the
         action value  is reset to SIG_DFL  and the subroutine
         is  called with  sig  passed as  its parameter.   The
         gsignal subroutine returns the value that is returned
         by the signal-handling subroutine.

     o   If the procedure for sig is an illegal value or if no
         procedure was  ever specified  for that  signal, then
         gsignal  returns a  value  of 0  and  takes no  other
         action.

     Related Information

     In this book:  "kill" and "signal."