sigvec(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

SIGVEC(3)               Linux Programmer's Manual              SIGVEC(3)

NAME         top

       sigvec, sigblock, sigsetmask, siggetmask, sigmask - BSD signal
       API

SYNOPSIS         top

       #include <signal.h>

       int sigvec(int sig, const struct sigvec *vec, struct sigvec *ovec);

       int sigmask(int signum);

       int sigblock(int mask);
       int sigsetmask(int mask);
       int siggetmask(void);

   Feature Test Macro Requirements for glibc (see
   feature_test_macros(7)):

       All functions shown above:
           Since glibc 2.19:
               _DEFAULT_SOURCE
           Glibc 2.19 and earlier:
               _BSD_SOURCE

DESCRIPTION         top

       These functions are provided in glibc as a compatibility
       interface for programs that make use of the historical BSD signal
       API.  This API is obsolete: new applications should use the POSIX
       signal API (sigaction(2), sigprocmask(2), etc.).

       The sigvec() function sets and/or gets the disposition of the
       signal sig (like the POSIX sigaction(2)).  If vec is not NULL, it
       points to a sigvec structure that defines the new disposition for
       sig.  If ovec is not NULL, it points to a sigvec structure that
       is used to return the previous disposition of sig.  To obtain the
       current disposition of sig without changing it, specify NULL for
       vec, and a non-null pointer for ovec.

       The dispositions for SIGKILL and SIGSTOP cannot be changed.

       The sigvec structure has the following form:

           struct sigvec {
               void (*sv_handler)(int); /* Signal disposition */
               int    sv_mask;          /* Signals to be blocked in handler */
               int    sv_flags;         /* Flags */
           };

       The sv_handler field specifies the disposition of the signal, and
       is either: the address of a signal handler function; SIG_DFL,
       meaning the default disposition applies for the signal; or
       SIG_IGN, meaning that the signal is ignored.

       If sv_handler specifies the address of a signal handler, then
       sv_mask specifies a mask of signals that are to be blocked while
       the handler is executing.  In addition, the signal for which the
       handler is invoked is also blocked.  Attempts to block SIGKILL or
       SIGSTOP are silently ignored.

       If sv_handler specifies the address of a signal handler, then the
       sv_flags field specifies flags controlling what happens when the
       handler is called.  This field may contain zero or more of the
       following flags:

       SV_INTERRUPT
              If the signal handler interrupts a blocking system call,
              then upon return from the handler the system call is not
              restarted: instead it fails with the error EINTR.  If this
              flag is not specified, then system calls are restarted by
              default.

       SV_RESETHAND
              Reset the disposition of the signal to the default before
              calling the signal handler.  If this flag is not
              specified, then the handler remains established until
              explicitly removed by a later call to sigvec() or until
              the process performs an execve(2).

       SV_ONSTACK
              Handle the signal on the alternate signal stack
              (historically established under BSD using the obsolete
              sigstack() function; the POSIX replacement is
              sigaltstack(2)).

       The sigmask() macro constructs and returns a "signal mask" for
       signum.  For example, we can initialize the vec.sv_mask field
       given to sigvec() using code such as the following:

           vec.sv_mask = sigmask(SIGQUIT) | sigmask(SIGABRT);
                       /* Block SIGQUIT and SIGABRT during
                          handler execution */

       The sigblock() function adds the signals in mask to the process's
       signal mask (like POSIX sigprocmask(SIG_BLOCK)), and returns the
       process's previous signal mask.  Attempts to block SIGKILL or
       SIGSTOP are silently ignored.

       The sigsetmask() function sets the process's signal mask to the
       value given in mask (like POSIX sigprocmask(SIG_SETMASK)), and
       returns the process's previous signal mask.

       The siggetmask() function returns the process's current signal
       mask.  This call is equivalent to sigblock(0).

RETURN VALUE         top

       The sigvec() function returns 0 on success; on error, it returns
       -1 and sets errno to indicate the error.

       The sigblock() and sigsetmask() functions return the previous
       signal mask.

       The sigmask() macro returns the signal mask for signum.

ERRORS         top

       See the ERRORS under sigaction(2) and sigprocmask(2).

VERSIONS         top

       Starting with version 2.21, the GNU C library no longer exports
       the sigvec() function as part of the ABI.  (To ensure backward
       compatibility, the glibc symbol versioning scheme continues to
       export the interface to binaries linked against older versions of
       the library.)

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).

       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │Interface                             Attribute     Value   │
       ├──────────────────────────────────────┼───────────────┼─────────┤
       │sigvec(), sigmask(), sigblock(),      │ Thread safety │ MT-Safe │
       │sigsetmask(), siggetmask()            │               │         │
       └──────────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO         top

       All of these functions were in 4.3BSD, except siggetmask(), whose
       origin is unclear.  These functions are obsolete: do not use them
       in new programs.

NOTES         top

       On 4.3BSD, the signal() function provided reliable semantics (as
       when calling sigvec() with vec.sv_mask equal to 0).  On System V,
       signal() provides unreliable semantics.  POSIX.1 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.

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                          2021-03-22                      SIGVEC(3)

Pages that refer to this page: sgetmask(2)sigaction(2)signal(2)sigpause(3)sigset(3)signal(7)