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sigaction 函数原型

int sigaction(int signum, const struct sigaction *act,struct sigaction *oldact);

sigaction 函数功能

•函数功能：给信号设置新的注册函数act，同时保留原有的信号处理函数在oldact
–执行某些信号时屏蔽某些信号，直接给sa_mask赋值即可
–处理带参数的信号
–一次注册，长期有效

struct sigaction { void (*sa_handler)(int); void (*sa_sigaction)(int, siginfo_t *, void *); sigset_t sa_mask; int sa_flags; void (*sa_restorer)(void); };

sigqueue 函数原型

int sigqueue (pid_t pid, int sig, const union sigval value);

sigqueue 函数功能

–用法与kill类似 –与kill不同之处：kill可以将 pid 设置为指定负值，向整个进程发送信号 –可以给指定进程传递一个int型数据 –sigaction 和 sigqueue 是一对 CP

一些经验

•一旦给信号安装了handler，它就一直有效
•信号的handler存在并发访问、可重入问题
•在信号的handler运行期间，会阻塞掉当前本身该信号
•在handler运行期间，当前信号的多次提交可能被丢弃，只保留一次
•除了本身信号是被阻塞的，可以通过设置，阻塞设定的一些信号
•signal是标准C定义的函数，而sigaction是POSIX接口函数
•Signal是对sigaction的封装
•不同的架构、操作系统对信号的value、default action 可能不一样
•特殊的两个信号：SIGKILL和SIGSTOP
–不能被忽略
–不能安装signal handler、不能被捕捉
–不能被阻塞

示例

signal

#include <signal.h> #include <unistd.h> #include <stdio.h> void handler (int signo) { int i,j; switch (signo) { case SIGHUP: printf ("get a SIGHUP signal: %d\n", signo); break; case SIGINT: printf ("get a SIGINT signal: %d\n", signo); break; case SIGQUIT: printf ("get a SIGQUIT signal: %d\n", signo); break; case SIGUSR1: printf ("get a SIGUSR1 signal: %d\n", signo); break; default: printf ("unknow signal\n"); } for (i = 0; i < 10000; i++) { for (j = 0; j < 1000; j++) ; } printf ("handler exit with signo: %d\n", signo); } int main (void) { signal (SIGHUP, handler); signal (SIGINT, handler); signal (SIGQUIT, handler); signal (SIGUSR1, handler); while (1); return 0; } //test 1: // run: kill -HUP 22380 // run: kill -HUP 22380 // run: kill -HUP 22380 // run: kill -HUP 22380 // run: kill -HUP 22380 //test 2: // run: kill -HUP 22380 // run: kill -INT 22380 // run: kill -QUIT 22380 // run: kill -USR1 22380 // run: kill -HUP 22380

sigaction 和 sigqueue CP交互

sigaction

#include <unistd.h> #include <signal.h> #include <stdio.h> void signal_handler (int signum) { printf ("signal_handler\n"); switch (signum) { case SIGHUP: printf ("get signal: SIGHUP\n"); sleep (20); break; case SIGINT: printf ("get signal: SIGINT\n"); break; case SIGQUIT: printf ("get signal: SIGQUIT\n"); break; case SIGUSR1: printf ("get signal: SIGUSR1\n"); break; default: printf ("undefined signal\n"); } } void signal_sigaction (int signum, siginfo_t *parm, void *parm2) { printf ("signal_sigaction\n"); switch (signum) { case SIGHUP: printf ("get signal: SIGHUP\n"); break; case SIGINT: printf ("get signal: SIGINT\n"); break; case SIGQUIT: printf ("get signal: SIGQUIT\n"); break; case SIGUSR1: printf ("get signal: SIGUSR1\n"); } printf ("received data: %d\n", parm->si_value); printf ("sending signal process pid : %d\n", parm->si_pid); } int main (void) { struct sigaction act, old_act; act.sa_sigaction = signal_sigaction; act.sa_handler = signal_handler; sigemptyset (&act.sa_mask); sigaddset (&act.sa_mask, SIGUSR1); act.sa_flags = 0; //sa_flags must be set,or it will cause core dump //set 0 may cause signal losing //act.sa_flags = SA_RESETHAND | SA_NODEFER; //SA_RESETHAND: restore signal action to DEF //SA_SIGINFO: use sa_sigaction as signal handler //SA_NODEFER: umask sa_mask sigaction (SIGHUP, &act, &old_act); // sigaction (SIGINT, &act, &old_act); // sigaction (SIGQUIT, &act, &old_act); // sigaction (SIGUSR1, &act, &old_act); while (1); return 0; }

sigqueue

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <signal.h> int main (int argc, char *argv[]) { union sigval val; val.sival_int = 10; pid_t pid = atoi (argv[1]); if (sigqueue (pid, SIGHUP, val) == -1) { perror ("sigqueue"); exit (EXIT_FAILURE); } printf ("current pid:%d\n", getpid()); return 0; }