SIGSETOPS(3)                                                      SIGSETOPS(3)


NAME
     sigsetops: sigaddset, sigdelset, sigemptyset, sigfillset, sigismember,
     sgi_altersigs, sgi_sigffset, sgi_siganyset, sgi_dumpset - signal set
     manipulation and examination routines (POSIX, with SGI-specific
     additions)

SYNOPSIS
   POSIX
     #include <signal.h>

     int sigaddset(sigset_t *set, int sig);

     int sigdelset(sigset_t *set, int sig);

     int sigemptyset(sigset_t *set);

     int sigfillset(sigset_t *set);

     int sigismember(sigset_t *set, int sig);

   SGI
     int sgi_altersigs(int action, sigset_t *set, int sigarray[]);

     int sgi_sigffset(sigset_t *set, int clearit);

     int sgi_siganyset(sigset_t *set);

     int sgi_dumpset(sigset_t *set);

DESCRIPTION
     These library calls modify or return information about the disposition of
     the signal mask pointed to by set. The system defines a set of signals
     that may be delivered to a process.  Signal delivery resembles the
     occurrence of a hardware interrupt:  the signal is blocked from further
     occurrence, the current process context is saved, and a new one is built.
     A global signal mask defines the set of signals currently blocked from
     delivery to a process; it may be changed with a sigprocmask(2) call.  The
     masks submitted as parameters to sigprocmask, sigaction, and sigsuspend
     and returned by sigpending may be constructed, altered, and examined via
     the sigsetops described in this man page.  They do NOT themselves alter
     the global signal mask.  The masks that the routines manipulate are of
     type sigset_t.

     sigaddset adds sig to the specified set.

     sigdelset deletes sig from the specified set.

     sigemptyset clears all signals in the specified set.

     sigfillset sets all signals in the specified set.


     sigismember returns 1 if sig is a member of the specified set, else
     returns 0.

SGI-SPECIFIC FUNCTIONS
     The following four functions, although not part of the POSIX
     specification, provide additional capabilities:

     sgi_altersigs performs action on the specified signal set, for each
     signal in sigarray. Action may be ADDSIGS or DELSIGS (defined in
     <sys/signal.h).  The final signal entry in sigarray must be followed by a
     0 entry (in this way sgi_altersigs knows how many signals to process).
     The array may include all legal signals; however, if the intent is to set
     or clear all signals the sigaddset and sigdelset routines are more
     efficient.  Any illegal signal numbers are silently skipped.
     sgi_altersigs returns the number of signals which were processed, or -1
     with errno set to [EINVAL] if action is not ADDSIGS or DELSIGS.

     sgi_sigffset returns the number of the lowest pending signal in set. If
     none are pending, it returns 0.  If clearit is non-zero, the returned
     signal is cleared in the mask.  In this way sgi_sigffset may be used to
     sequentially examine the signals in a mask without duplication.

     sgi_siganyset(set) returns 1 if any signals are set in the specified
     mask, otherwise it returns 0.  The mask is not altered.

     sgi_dumpset displays the specified set of signals as a bit-vector,
     primarily for debugging purposes.

     For a list of valid signal numbers please see signal(5).

ERRORS
     In every routine, the set parameter is a pointer to sigset_t.  All of
     these functions are library routines (executing in user space); therefore
     if they are passed a REFERENCE to set instead of a POINTER, the compiler
     will issue a warning, and when the program is run the process will
     receive a memory fault signal [SIGSEGV] and terminate (unless the process
     has installed a handler for SIGSEGV).

     All routines which require a sig parameter will fail, returning -1 and
     setting errno to [EINVAL] if sig is not a valid signal number.

SEE ALSO
     sigaction(2), sigprocmask(2), sigpending(2), sigsuspend(2), sigsetjmp(3),
     pthread_sigmask(3P).

WARNING
     The POSIX and System V signal facilities have different semantics.  Using
     both facilities in the same program is strongly discouraged and will
     result in unpredictable behavior.


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