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NAME
sigvec, sigblock, sigsetmask, siggetmask, sigmask - BSD signal API
SYNOPSIS
#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: _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 This API is obsolete: new applications should use the POSIX signal API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 will not be restarted: instead it will fail 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(), │ Thread safety │ MT-Safe │
│ sigsetmask(), siggetmask() │ │ │
└──────────────────────────────────┴───────────────┴─────────┘
VERSIONS
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.)
CONFORMING TO
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
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)
COLOPHON
This page is part of release 4.04 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
http://www.kernel.org/doc/man-pages/.
Linux 2015-03-02 SIGVEC(3)