SIGHOLD(P)						     POSIX Programmer's Manual							SIGHOLD(P)

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 execut-
       ing 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  pro-
       cesses  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  sigac-
       tion() 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 Technol-
       ogy -- 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)