NAME

       sighold, sigignore, sigpause, sigrelse, sigset - signal management

SYNOPSIS

       #include <signal.h>

       int sighold(int sig);
       int sigignore(int sig);
       int sigpause(int sig);
       int sigrelse(int sig);
       void (*sigset(int sig, void (*disp)(int)))(int);

DESCRIPTION

       Use of any of these functions is unspecified in a multi-threaded process.

       The  sighold(),  sigignore(),  sigpause(),  sigrelse(),  and sigset() functions provide simplified signal
       management.

       The sigset() function shall modify signal dispositions. The sig argument specifies the signal, which  may
       be any signal except SIGKILL and SIGSTOP. The disp argument specifies the signal's disposition, which may
       be  SIG_DFL, SIG_IGN, or the address of a signal handler. If sigset() is used, and disp is the address of
       a signal handler, the system shall add sig to the calling  process'  signal  mask  before  executing  the
       signal  handler;  when  the  signal handler returns, the system shall restore the calling process' signal
       mask to its state prior to the delivery of the signal. In addition, if sigset()  is  used,  and  disp  is
       equal  to  SIG_HOLD,  sig  shall be added to the calling process' signal mask and sig's disposition shall
       remain unchanged. If sigset() is used, and disp is not equal to SIG_HOLD, sig shall be removed  from  the
       calling process' signal mask.

       The sighold() function shall add sig to the calling process' signal mask.

       The sigrelse() function shall remove sig from the calling process' signal mask.

       The sigignore() function shall set the disposition of sig to SIG_IGN.

       The  sigpause()  function  shall remove sig from the calling process' signal mask and suspend the calling
       process until a signal is received. The sigpause() function shall restore the process' signal mask to its
       original state before returning.

       If the action for the SIGCHLD signal is set to SIG_IGN, child processes of the  calling  processes  shall
       not  be  transformed into zombie processes when they terminate. If the calling process subsequently waits
       for its children, and the process  has  no  unwaited-for  children  that  were  transformed  into  zombie
       processes,  it shall block until all of its children terminate, and wait(), waitid(), and waitpid() shall
       fail and set errno to [ECHILD].

RETURN VALUE

       Upon successful completion, sigset() shall return SIG_HOLD  if  the  signal  had  been  blocked  and  the
       signal's  previous disposition if it had not been blocked. Otherwise, SIG_ERR shall be returned and errno
       set to indicate the error.

       The sigpause() function shall suspend execution of the thread until a signal is  received,  whereupon  it
       shall return -1 and set errno to [EINTR].

       For  all  other  functions,  upon  successful  completion,  0  shall be returned.  Otherwise, -1 shall be
       returned and errno set to indicate the error.

ERRORS

       These functions shall fail if:

       EINVAL The sig argument is an illegal signal number.

       The sigset() and sigignore() functions shall fail if:

       EINVAL An attempt is made to catch a signal that cannot be caught, or to ignore a signal that  cannot  be
              ignored.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       The  sigaction()  function  provides a more comprehensive and reliable mechanism for controlling signals;
       new applications should use sigaction() rather than sigset().

       The sighold() function, in conjunction with sigrelse() or sigpause(), may be used to  establish  critical
       regions of code that require the delivery of a signal to be temporarily deferred.

       The sigsuspend() function should be used in preference to sigpause() for broader portability.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Signal  Concepts  ,  exec()  ,  pause()  ,  sigaction()  ,  signal() , sigsuspend() , waitid() , the Base
       Definitions volume of IEEE Std 1003.1-2001, <signal.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
       Inc  and  The  Open Group. In the event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                                   2003                                            SIGHOLD(P)