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sigset(3) — Linux manual page

sigset(3) Library Functions Manual sigset(3)

NAME top

 sigset, sighold, sigrelse, sigignore - System V signal API

LIBRARY top

 Standard C library (libc, -lc)

SYNOPSIS top

 #include <signal.h>
 typedef typeof(void (int)) *sighandler_t;
 [[deprecated]] sighandler_t sigset(int sig, sighandler_t disp);
 [[deprecated]] int sighold(int sig);
 [[deprecated]] int sigrelse(int sig);
 [[deprecated]] int sigignore(int sig);
 Feature Test Macro Requirements for glibc (see
 feature_test_macros(7)):
 sigset(), sighold(), sigrelse(), sigignore():
 _XOPEN_SOURCE >= 500

DESCRIPTION top

 These functions are provided in glibc as a compatibility interface
 for programs that make use of the historical System V signal API.
 This API is obsolete: new applications should use the POSIX signal
 API (sigaction(2), sigprocmask(2), etc.)
 The sigset() function modifies the disposition of the signal sig.
 The disp argument can be the address of a signal handler function,
 or one of the following constants:
 SIG_DFL
 Reset the disposition of sig to the default.
 SIG_IGN
 Ignore sig.
 SIG_HOLD
 Add sig to the process's signal mask, but leave the
 disposition of sig unchanged.
 If disp specifies the address of a signal handler, then sig is
 added to the process's signal mask during execution of the
 handler.
 If disp was specified as a value other than SIG_HOLD, then sig is
 removed from the process's signal mask.
 The dispositions for SIGKILL and SIGSTOP cannot be changed.
 The sighold() function adds sig to the calling process's signal
 mask.
 The sigrelse() function removes sig from the calling process's
 signal mask.
 The sigignore() function sets the disposition of sig to SIG_IGN.

RETURN VALUE top

 On success, sigset() returns SIG_HOLD if sig was blocked before
 the call, or the signal's previous disposition if it was not
 blocked before the call. On error, sigset() returns -1, with
 errno  set to indicate the error. (But see BUGS below.)
 The sighold(), sigrelse(), and sigignore() functions return 0 on
 success; on error, these functions return -1 and set errno  to
 indicate the error.

ERRORS top

 For sigset() see the ERRORS under sigaction(2) and sigprocmask(2).
 For sighold() and sigrelse() see the ERRORS under sigprocmask(2).
 For sigignore(), see the errors under sigaction(2).

ATTRIBUTES top

 For an explanation of the terms used in this section, see
 attributes(7).
 ┌──────────────────────────────────────┬───────────────┬─────────┐
 │ Interface │ Attribute │ Value │
 ├──────────────────────────────────────┼───────────────┼─────────┤
 │ sigset(), sighold(), sigrelse(), │ Thread safety │ MT-Safe │
 │ sigignore() │ │ │
 └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

 POSIX.1-2008.
 sighandler_t
 GNU. POSIX.1 uses the same type but without a typedef.

HISTORY top

 glibc 2.1. SVr4, POSIX.1-2001. POSIX.1-2008 marks these
 functions as obsolete, recommending the use of sigaction(2),
 sigprocmask(2), pthread_sigmask(3), and sigsuspend(2) instead.

NOTES top

 The sigset() function provides reliable signal handling semantics
 (as when calling sigaction(2) with sa_mask equal to 0).
 On System V, the signal() function provides unreliable semantics
 (as when calling sigaction(2) with sa_mask equal to SA_RESETHAND |
 SA_NODEFER). On BSD, signal() provides reliable semantics.
 POSIX.1-2001 leaves these aspects of signal() unspecified. See
 signal(2) for further details.
 In order to wait for a signal, BSD and System V both provided a
 function named sigpause(3), but this function has a different
 argument on the two systems. See sigpause(3) for details.

BUGS top

 Before glibc 2.2, sigset() did not unblock sig if disp was
 specified as a value other than SIG_HOLD.
 Before glibc 2.5, sigset() does not correctly return the previous
 disposition of the signal in two cases. First, if disp is
 specified as SIG_HOLD, then a successful sigset() always returns
 SIG_HOLD. Instead, it should return the previous disposition of
 the signal (unless the signal was blocked, in which case SIG_HOLD
 should be returned). Second, if the signal is currently blocked,
 then the return value of a successful sigset() should be SIG_HOLD.
 Instead, the previous disposition of the signal is returned.
 These problems have been fixed since glibc 2.5.

SEE ALSO top

 kill(2), pause(2), sigaction(2), signal(2), sigprocmask(2),
 raise(3), sigpause(3), sigvec(3), signal(7)

COLOPHON top

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 user-space interface documentation) project. Information about
 the project can be found at 
 ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
 for this manual page, see
 ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
 This page was obtained from the tarball man-pages-6.10.tar.gz
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 ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
 2025年02月02日. If you discover any rendering problems in this HTML
 version of the page, or you believe there is a better or more up-
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 man-pages@man7.org
Linux man-pages 6.10 2024年12月13日 sigset(3)

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Pages that refer to this page: sigvec(3), signal(7), signal-safety(7)

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