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:
_DEFAULT_SOURCE
Glibc 2.19 and earlier:
_BSD_SOURCE
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 This API is obsolete: new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 s not be 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).
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.
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 library.)
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 |
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)