sigvec

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

#define _BSD_SOURCE
#include <signal.h> I int sigvec(int sig , struct sigvec * vec , struct sigvec * ovec ); I int sigmask(int signum ); I int sigblock(int mask ); I int sigsetmask(int mask ); int siggetmask(void);

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 This API is obsolete: new applications should use the POSIX signal API (sigaction(2), sigprocmask(2), etc.)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 R 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 R sig . If ovec is not NULL, it points to a sigvec structure that is used to return the previous disposition of R sig . To obtain the current disposition of sig without changing it, specify NULL for R vec , and a non-NULL pointer for R ovec . The dispositions for SIGKILL and SIGSTOP cannot be changed. The sigvec structure has the following form:

struct sigvec {
    void (*sv_handler)();  /* 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; or 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 by default. 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

SV_RESETHAND

SV_ONSTACK

The R sigmask () function constructs and returns a "signal mask" for R signum . For example, we can initialize the vec.sv_mask field given to R sigvec () using code such as the following:

    vec.sv_mask = sigmask(SIGQUIT) | sigpause(SIGABRT);
                /* Block SIGQUIT and SIGABRT during
                   handler execution */

The R sigblock () function adds the signals in mask to the process's signal mask (like POSIX R sigprocmask(SIG_BLOCK) ), and returns the process's previous signal mask. Attempts to block SIGKILL or SIGSTOP are silently ignored.

The R sigsetmask () function sets the process's signal mask to the value given in mask (like POSIX R sigprocmask(SIG_SETMASK) ), and returns the process's previous signal mask.

The R siggetmask () function returns the process's current signal mask. This call is equivalent to R sigblock(0) .

The R sigvec () function returns 0 on success; on error, it returns -1 and sets errno to indicate the error. The R sigblock () and R sigsetmask () functions return the previous signal mask. The R sigmask () function returns the signal mask for R signum .

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

All of these functions were in 4.3BSD, except R siggetmask (), whose origin is unclear. These functions are obsolete: do not use them in new programs.

On 4.3BSD, the R signal () function provided reliable semantics (as when calling R sigvec () with vec.sv_mask equal to 0). On System V, R signal () provides unreliable semantics. POSIX.1-2001 leaves these aspects of R signal () unspecified. See signal(2) for further details. In order to wait for a signal, BSD and System V both provided a function named R sigpause (), 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), feature_test_macros(7), signal(7)