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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 simpli-
       fied 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  han-
       dler.  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 dispo-
       sition 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 call-
       ing process subsequently waits for its children, and the process has no unwaited-for chil-
       dren 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 control-
       ling 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 portabil-
       ity.

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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				       SIGHOLD(P)
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