Linux中信号处理的两种方法

1、使用signal()函数和sigaction()

signal()函数原型 

       #include <signal.h>       typedef void (*sighandler_t)(int);       sighandler_t signal(int signum, sighandler_t handler);              signal() sets the disposition of the signal signum to handler, which is       either SIG_IGN, SIG_DFL, or the address of a  programmer-defined  function (a "signal handler")

The signals SIGKILL and SIGSTOP cannot be caught or ignored. ——即信号SIGKILL和信号SIGSTOP不能被捕获或者忽略。

sigaction()函数原型

NAME<pre>       sigaction - examine and change a signal actionSYNOPSIS       #include <signal.h>       int sigaction(int signum, const struct sigaction *act,                     struct sigaction *oldact);   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):       sigaction(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE       If act is non-NULL, the new action for signal signum is installed  fromact.  If oldact is non-NULL, the previous action is saved in oldact.The sigaction structure is defined as something like:   struct sigaction {       void     (*sa_handler)(int);       void     (*sa_sigaction)(int, siginfo_t *, void *);       sigset_t   sa_mask;       int        sa_flags;       void     (*sa_restorer)(void);   };On  some  architectures  a  union  is  involved:  do not assign to bothsa_handler and sa_sigaction.The sa_restorer element is obsolete and should not be used.  POSIX doesnot specify a sa_restorer element.

#include <stdio.h>#include <stdlib.h>#include <signal.h>/* Define the signal handle function */void my_func(int sig_no){switch(sig_no){case SIGINT:printf("I have get SIGINT\n");break;case SIGQUIT:printf("I have get SIGQUIT\n");break;default:break;}}int main(){struct sigaction action;printf("Waiting for signal SIGINT or SIGQUIT...\n");/* Initialize the sigaction structure*/action.sa_handler = my_func;sigemptyset(&action.sa_mask);action.sa_flags = 0;/* Send certain signal and go to handle_fun */sigaction(SIGINT, &action, 0);sigaction(SIGQUIT, &action, 0);pause();alarm(3);printf("I'm over!\n");exit(0);}

2、使用信号集函数组

调用的函数主要包括一下4个功能模块，创建信号集、注册信号处理函数及检测信号。sigemptyset()：将信号集初始化为空sigfillset():  将信号集初始化为包含所有已定义的信号集。sigaddset()： 将制定信号加入信号集中。sigdelset():   将指定信号从信号集中删除。sigismember():  查询指定信号是否在信号集中。
sigpending()函数允许进程检测“未处理“的信号，并进一步决定对它们做何处理。
说明：注册信号处理函数主要用于决定进程如何处理信号，注意：信号集中的信号并不是真正可以处理的信号，只有当信号的状态处于非阻塞状态时才会真正起作用。所以一般使用sigprocmask()函数检测并更改信号屏蔽字（信号屏蔽字是指用来指定当前被阻塞的一组信号，它们不会被进程接收），然后使用sigaction()函数来定义进程接收到特定信号的行为。信号处理的一般流程：
程序实例：首先把SIGQUIT、SIGINT两个信号加入信号集，然后将该信号集设为阻塞状态，并进入用户输入状态。用户只需按任意键就可以立即将信号集设为非阻塞状态，再对这两个信号分别进行操作，其中SIGQUIT执行默认操作，而SIGINT执行用户自定义函数的操作。

#include <stdio.h>#include <stdlib.h>#include <signal.h>#include <sys/types.h>/* Define the signal handle function */void my_func(int sig_no){printf("If you want to quit, please try SIGQUIT\n");}int main(){sigset_t set, pendset;struct sigaction action1, action2;/* step1: Initialize the sigset with Null. */if(sigemptyset(&set) < 0){perror("sigemptyset");exit(1);}/* Add certain signal to sigset */if(sigaddset(&set, SIGQUIT) < 0){perror("sigaddset");exit(1);}if(sigaddset(&set, SIGINT) < 0){perror("sigaddset");exit(1);}if(sigismember(&set, SIGINT) < 0){sigemptyset(&action1.sa_mask);action1.sa_handler = my_func;action1.sa_flags = 0;sigaction(SIGINT, &action1, NULL);}if(sigismember(&set, SIGQUIT) < 0){sigemptyset(&action2.sa_mask);action2.sa_handler = my_func;action2.sa_flags = 0;sigaction(SIGQUIT, &action2, NULL);}/* step2: Set the value of mask word */if(sigprocmask(SIG_BLOCK, &set, NULL) < 0){perror("sigprocmask");exit(1);}else{printf("Signal set was blocked, Press any key!\n");getchar();}/* Delete the signal of set */if(sigprocmask(SIG_UNBLOCK, &set, NULL) < 0){perror("sigprocmask");exit(1);}else{printf("Signal set was unblocked, Press any key!\n");}while(1);exit(0);}