sigvec(3) Library Functions Manual sigvec(3)
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 This API is
obsolete: new applications should use the POSIX signal API (sigac-
tion(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 ei-
ther: the address of a signal handler function; SIG_DFL, meaning the de-
fault 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 ig-
nored.
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 spec-
ified, 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 han-
dler 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 es-
tablished 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 pre-
vious 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() │ │ │
└────────────────────────────────────────────┴───────────────┴─────────┘
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)
Linux man-pages 6.9.1 2024-05-02 sigvec(3)
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