sigset(3) - Linux manual page (original) (raw)

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   This API is obsolete: new applications should use the POSIX signal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)](../man2/sigaction.2.html), [sigprocmask(2)](../man2/sigprocmask.2.html), 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](../man3/errno.3.html)_ 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](../man3/errno.3.html)_ to
   indicate the error.

ERRORS top

   For **sigset**() see the ERRORS under [sigaction(2)](../man2/sigaction.2.html) and [sigprocmask(2)](../man2/sigprocmask.2.html).

   For **sighold**() and **sigrelse**() see the ERRORS under [sigprocmask(2)](../man2/sigprocmask.2.html).

   For **sigignore**(), see the errors under [sigaction(2)](../man2/sigaction.2.html).

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **sigset**(), **sighold**(), **sigrelse**(),     │ Thread safety │ MT-Safe │
   │ **sigignore**()                          │               │         │
   └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

   POSIX.1-2008.

   _sighandlert_
          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)](../man2/sigaction.2.html),
   [sigprocmask(2)](../man2/sigprocmask.2.html), [pthread_sigmask(3)](../man3/pthread%5Fsigmask.3.html), and [sigsuspend(2)](../man2/sigsuspend.2.html) instead.

NOTES top

   The **sigset**() function provides reliable signal handling semantics
   (as when calling [sigaction(2)](../man2/sigaction.2.html) with _samask_ equal to 0).

   On System V, the **signal**() function provides unreliable semantics
   (as when calling [sigaction(2)](../man2/sigaction.2.html) with _samask_ equal to _SARESETHAND |_
   _SANODEFER_).  On BSD, **signal**() provides reliable semantics.
   POSIX.1-2001 leaves these aspects of **signal**() unspecified.  See
   [signal(2)](../man2/signal.2.html) for further details.

   In order to wait for a signal, BSD and System V both provided a
   function named [sigpause(3)](../man3/sigpause.3.html), but this function has a different
   argument on the two systems.  See [sigpause(3)](../man3/sigpause.3.html) 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)](../man2/kill.2.html), [pause(2)](../man2/pause.2.html), [sigaction(2)](../man2/sigaction.2.html), [signal(2)](../man2/signal.2.html), [sigprocmask(2)](../man2/sigprocmask.2.html),
   [raise(3)](../man3/raise.3.html), [sigpause(3)](../man3/sigpause.3.html), [sigvec(3)](../man3/sigvec.3.html), [signal(7)](../man7/signal.7.html)

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Linux man-pages 6.10 2024-12-13 sigset(3)

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