sighold(3p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

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

NAME         top

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

SYNOPSIS         top

       #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         top

       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 signal mask of
       the calling process before executing the signal handler; when the
       signal handler returns, the system shall restore the signal mask
       of the calling process 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 signal mask of the calling
       process 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 signal mask of the calling process.

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

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

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

       The sigpause() function shall remove sig from the signal mask of
       the calling process and suspend the calling process until a
       signal is received. The sigpause() function shall restore the
       signal mask of the process 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         top

       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         top

       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         top

       None.

APPLICATION USAGE         top

       The sigaction() function provides a more comprehensive and
       reliable mechanism for controlling signals; new applications
       should use the sigaction() function instead of the obsolescent
       sigset() function.

       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.
       For broader portability, the pthread_sigmask() or sigprocmask()
       functions should be used instead of the obsolescent sighold() and
       sigrelse() functions.

       For broader portability, the sigsuspend() function should be used
       instead of the obsolescent sigpause() function.

RATIONALE         top

       Each of these historic functions has a direct analog in the other
       functions which are required to be per-thread and thread-safe
       (aside from sigprocmask(), which is replaced by
       pthread_sigmask()).  The sigset() function can be implemented as
       a simple wrapper for sigaction().  The sighold() function is
       equivalent to sigprocmask() or pthread_sigmask() with SIG_BLOCK
       set. The sigignore() function is equivalent to sigaction() with
       SIG_IGN set. The sigpause() function is equivalent to
       sigsuspend().  The sigrelse() function is equivalent to
       sigprocmask() or pthread_sigmask() with SIG_UNBLOCK set.

FUTURE DIRECTIONS         top

       These functions may be removed in a future version.

SEE ALSO         top

       Section 2.4, Signal Concepts, exec(1p), pause(3p),
       pthread_sigmask(3p), sigaction(3p), signal(3p), sigsuspend(3p),
       wait(3p), waitid(3p)

       The Base Definitions volume of POSIX.1‐2017, signal.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                       SIGHOLD(3P)

Pages that refer to this page: signal.h(0p)sigpause(3p)sigrelse(3p)