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

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

       #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:
           Glibc 2.19 and earlier:

       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  This API is
       obsolete: new applications should use the POSIX signal API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

       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

       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:

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

              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

              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).

       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

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

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

       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

       For an explanation of the terms used in this section, see

       │Interface                        Attribute     Value   │
       │sigvec(), sigmask(), sigblock(), │ Thread safety │ MT-Safe │
       │sigsetmask(), siggetmask()       │               │         │
       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.

       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.

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

       This page is part of release 5.05 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

Linux                             2017-09-15                         SIGVEC(3)