SIGHOLD(3P)                                         POSIX Programmer's Manual                                        SIGHOLD(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

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 return-
       ing.

       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 termi-
       nate, 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 dis-
       position 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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   SIGHOLD(3P)