linux sigemptyset, sigfillset, sigaddset, sigdelset, sigismember 以及sigsuspend

man sigemptyset

NAME
sigemptyset, sigfillset, sigaddset, sigdelset, sigismember - POSIX signal set operations.

SYNOPSIS
#include <signal.h>

int sigemptyset(sigset_t *set);

int sigfillset(sigset_t *set);

int sigaddset(sigset_t *set, int signum);

int sigdelset(sigset_t *set, int signum);

int sigismember(const sigset_t *set, int signum);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

sigemptyset(), sigfillset(), sigaddset(), sigdelset(), sigismember(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE

DESCRIPTION
These functions allow the manipulation of POSIX signal sets.

sigemptyset() initializes the signal set given by set to empty, with all signals excluded from the set.

sigfillset() initializes set to full, including all signals.

sigaddset() and sigdelset() add and delete respectively signal signum from set.

sigismember() tests whether signum is a member of set.

Objects  of  type  sigset_t must be initialized by a call to either sigemptyset() or sigfillset() before being passed to the functions sigaddset(), sigdelset() and
sigismember() or the additional glibc functions described below (sigisemptyset(), sigandset(), and sigorset()).  The results are undefined if this is not done.

RETURN VALUE
sigemptyset(), sigfillset(), sigaddset(), and sigdelset() return 0 on success and -1 on error.

sigismember() returns 1 if signum is a member of set, 0 if signum is not a member, and -1 on error.

ERRORS
EINVAL sig is not a valid signal.

CONFORMING TO
POSIX.1-2001.

NOTES
Glibc Notes
If the _GNU_SOURCE feature test macro is defined, then <signal.h> exposes three other functions for manipulating signal sets.

int sigisemptyset(sigset_t *set);
returns 1 if set contains no signals, and 0 otherwise.

int sigorset(sigset_t *dest, sigset_t *left, sigset_t *right);
places the union of the sets left and right in dest.

int sigandset(sigset_t *dest, sigset_t *left, sigset_t *right);
places the intersection of the sets left and right in dest.

sigorset() and sigandset() return 0 on success, and -1 on failure.

These functions are non-standard (a few other systems provide similar functions) and their use should be avoided in portable applications.

SEE ALSO
sigaction(2), sigpending(2), sigprocmask(2), sigsuspend(2)

COLOPHON
This page is part of release 3.22 of the Linux man-pages project.  A  description  of  the  project,  and  information  about  reporting  bugs,  can  be  found  at http://www.kernel.org/doc/man-pages/. 
Linux                             2008-09-01                      SIGSETOPS(3)

man sigsuspend

NAME
sigsuspend - wait for a signal

SYNOPSIS
#include <signal.h>

int sigsuspend(const sigset_t *mask);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

sigsuspend(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE

DESCRIPTION
sigsuspend() temporarily replaces the signal mask of the calling process with the mask given by mask and then suspends the process until delivery of a signal whose
action is to invoke a signal handler or to terminate a process.

If the signal terminates the process, then sigsuspend() does not return.  If the signal is caught, then sigsuspend() returns after the signal handler returns,  and
the signal mask is restored to the state before the call to sigsuspend().

It is not possible to block SIGKILL or SIGSTOP; specifying these signals in mask, has no effect on the process’s signal mask.

RETURN VALUE
sigsuspend() always returns -1, normally with the error EINTR.

ERRORS
EFAULT mask points to memory which is not a valid part of the process address space.

EINTR  The call was interrupted by a signal.

CONFORMING TO
POSIX.1-2001.

NOTES
Normally,  sigsuspend()  is  used in conjunction with sigprocmask(2) in order to prevent delivery of a signal during the execution of a critical code section.  The
caller first blocks the signals with sigprocmask(2).  When the critical code has completed, the caller then waits for the signals by calling sigsuspend() with  the
signal mask that was returned by sigprocmask(2) (in the oldset argument).

See sigsetops(3) for details on manipulating signal sets.

SEE ALSO
kill(2), pause(2), sigaction(2), signal(2), sigprocmask(2), sigwaitinfo(2), sigsetops(3), sigwait(3), signal(7)

COLOPHON
This  page  is  part  of  release  3.22  of  the  Linux  man-pages  project.   A  description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 
Linux

示例1： segemptyset()

#include <stdio.h>
#include <signal.h>

void handle(int s)
{
printf("interupt by external\n");
}

void main()
{
sigset_t set;

sigemptyset(&set);

if(sigismember(&set,SIGINT))
printf("sig int in main 0\n");
sigaddset(&set, SIGCHLD);
sigaddset(&set, SIGALRM);
sigaddset(&set, SIGIO);
sigaddset(&set, SIGINT);
signal(SIGINT,handle);

if (sigprocmask(SIG_BLOCK, &set, NULL) == -1) {
printf("sigprocmask() failed");
}

sigemptyset(&set);

if(sigismember(&set,SIGINT))
printf("sig int in main 1\n");

printf("finish test\n");
}

运行结果：

finish test

示例2：sigprocmask()和sigsuspend()

#include <stdio.h>
#include <signal.h>

void handle(int s)
{
printf("interupt by external\n");
}

void main()
{
sigset_t set;

sigemptyset(&set);

if(sigismember(&set,SIGINT))
printf("sig int in main 0\n");
sigaddset(&set, SIGCHLD);
sigaddset(&set, SIGALRM);
sigaddset(&set, SIGIO);
sigaddset(&set, SIGINT);
signal(SIGINT,handle);

if (sigprocmask(SIG_BLOCK, &set, NULL) == -1) {
printf("sigprocmask() failed");
}

sigemptyset(&set);

sigsuspend(&set);
printf("sigsuspend() after\n");

if(sigismember(&set,SIGINT))
printf("sig int in main 1\n");

printf("finish test\n");

}

运行结果，按住ctrl+c后：

^Cinterupt by external
sigsuspend() after
finish test

示例3，没有signal handler

#include <stdio.h>
#include <signal.h>

void handle(int s)
{
printf("interupt by external\n");
}

void main()
{
sigset_t set;

sigemptyset(&set);

if(sigismember(&set,SIGINT))
printf("sig int in main 0\n");
sigaddset(&set, SIGCHLD);
sigaddset(&set, SIGALRM);
sigaddset(&set, SIGIO);
sigaddset(&set, SIGINT);

if (sigprocmask(SIG_BLOCK, &set, NULL) == -1) {
printf("sigprocmask() failed");
}

sigemptyset(&set);

sigsuspend(&set);
printf("sigsuspend() after\n");

if(sigismember(&set,SIGINT))
printf("sig int in main 1\n");

printf("finish test\n");

}

运行结果，按住ctrl+c后，程序直接结束。

sigsuspend功能
1. 终止进程，对应示例3.
2. 如果捕获到信号，执行完handler后，sigsuspend返回，对应示例2.