NAME

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

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <signal.h>

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

       [[deprecated]] int sigmask(int signum);

       [[deprecated]] int sigblock(int mask);
       [[deprecated]] int sigsetmask(int mask);
       [[deprecated]] 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

       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  This API is obsolete: new applications  should  use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

       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

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

ATTRIBUTES

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

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

STANDARDS

       None.

HISTORY

       sigvec()
       sigblock()
       sigmask()
       sigsetmask()
              4.3BSD.

       siggetmask()
              Unclear origin.

       sigvec()
              Removed in glibc 2.21.

NOTES

       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

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