NAME

ssignal, gsignal − software signals

SYNOPSIS

#include <signal.h>

int (∗ssignal (sig, action))( )
int sig, (∗action)( );

int gsignal (sig)
int sig;

DESCRIPTION

Ssignal and gsignal implement a software facility similar to signal(2). This facility is used by the Standard C Library to enable the user to indicate the disposition of error conditions, and is also made available to the user for his own purposes.

Software signals made available to users are associated with integers in the inclusive range 1 through 15. An action for a software signal is established by a call to ssignal, and a software signal is raised by a call to gsignal. Raising a software signal causes the action established for that signal to be taken.

The first argument to ssignal is a number identifying the type of signal for which an action is to be established. The second argument defines the action; it is either the name of a (user defined) action function or one of the manifest constants SIG_DFL (default) or SIG_IGN (ignore).  Ssignal returns the action previously established for that signal type; if no action has been established or the signal number is illegal, ssignal returns SIG_DFL. 

Gsignal raises the signal identified by its argument, sig:

If an action function has been established for sig, then that action is reset to SIG_DFL and the action function is entered with argument sig. Gsignal returns the value returned to it by the action function. 

If the action for sig is SIG_IGN, gsignal returns the value 1 and takes no other action. 

If the action for sig is SIG_DFL, gsignal returns the value 0 and takes no other action. 

If sig has an illegal value or no action was ever specified for sig, gsignal returns the value 0 and takes no other action. 

NOTES

There are some additional signals with numbers outside the range 1 through 15 which are used by the Standard C Library to indicate error conditions.  Thus, some signal numbers outside the range 1 through 15 are legal, although their use may interfere with the operation of the Standard C Library.