Linux sigaction function (registration signal) use

int sigaction(intconststructstruct sigaction *oldact);

The function of the Sigaction function is to inspect or modify the processing action associated with the specified signal (both operations can be done simultaneously).

Parameter description:
Signum: Signal to operate
Act: A new way to set the signal to be processed
Oldact: The original Signal processing method
Return value: Successfully returned 0, failed return-1, and set errno

struct Sigaction structure prototype:

struct sigaction {    void     (*sa_handler)(int);  //老类型的信号处理函数指针，与 single 函数一样    void     (*sa_sigaction)(intvoid//新类型的信号处理函数指针    sigset_t   sa_mask;  //将要被阻塞的信号集合    int        sa_flags;  //信号处理方式    void     (*sa_restorer)(void//保留};

single 函数一样

The three parameters of the Sa_sigaction function pointer mean:intIsignnum: Incoming signal siginfo_t *psigninfo: Some information related to this signal, he is a struct prototype as follows siginfo_t {intSi_signo;/ * signal value, meaning for all signals * /    intSi_errno;/ * errno value, meaning for all signals * /    intSi_code;/ * The cause of the signal is meaningful for all signals * /    intSi_trapno;/* Trap number that caused hardware-generated signal (unused O N most architectures) * /pid_t Si_pid;/ * Process ID to send the signal * /uid_t Si_uid;/ * Real user ID for sending signal process * /    intSi_status;/ * to out state, meaning to SIGCHLD * /clock_t Si_utime;/ * User-consumed time, meaning for SIGCHLD * /clock_t Si_stime;/ * Time consumed by kernel, meaning for SIGCHLD * /sigval_t Si_value;/* Signal value, for all real-time meaningful, is a federated data structure that can be an integer (indicated by Si_int, or can be a pointer, by SI_PTR) * /    intSi_int;/ * POSIX.1B signal * /    void*si_ptr;/ * POSIX.1B signal * /    intSi_overrun;/ * Timer overrun count; POSIX.1B Timers * /    intSi_timerid;/ * Timer ID; POSIX.1B Timers * /    void*SI_ADDR;/ * Trigger fault memory address, meaning for sigill,sigfpe,sigsegv,sigbus signal * /    LongSi_band;/ * make sense for sigpoll signal * /    intSI_FD;/ * make sense for sigpoll signal * /     ShortSI_ADDR_LSB;/* Least significant bit of address (since kernel 2.6.32) */}void*preserved: All the information on the Internet is said to be (reserved, useless)

sa_mask ： 是一个包含信号集合的结构体，该结构体内的信号表示在进行信号处理时，将要被阻塞的信号。

sa_flags  是一组掩码的合成值，指示信号处理时所应该采取的一些行为，各掩码的含义为：SA_RESETHAND : 处理完毕要捕捉的信号后，将自动撤消信号处理函数的注册，即必须再重新注册信号处理函数，才能继续处理接下来产生的信号。SA_NODEFER : 在处理信号时，如果又发生了其它的信号，则立即进入其它信号的处理，等其它信号处理完毕后，再继续处理当前的信号，即递规地处理。如果sa_flags包含了该掩码，则结构体sigaction的sa_mask将无效；SA_RESTART : 如果在发生信号时，程序正阻塞在某个系统调用，例如调用read()函数，则在处理完毕信号后，接着从阻塞的系统返回。该掩码符合普通的程序处理流程，所以一般来说，应该设置该掩码，否则信号处理完后，阻塞的系统调用将会返回失败；SA_SIGINFO : 指示结构体的信号处理函数指针是哪个有效，如果sa_flags包含该掩码，则sa_sigactiion指针有效

Example:

#include <signal.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/types.h>#include <unistd.h>voidMy_sigaction (intSigNum, siginfo_t *siginfo,void*BUF) {Switch(SigNum) { CaseSIGUSR1:printf("recv form pid is%d, signal are SIGUSR1, Signum is%d\n", Siginfo->si_pid, Siginfo->si_signo); Break; CaseSIGUSR2:printf("recv form pid is%d, signal are SIGUSR2, Signum is%d\n", Siginfo->si_pid, Siginfo->si_signo); Break;default:printf("recv form pid is%d, Signum is%d\n", Siginfo->si_pid, Siginfo->si_signo); } Sleep (Ten);}intMainintargcChar*argv[]) {structSigaction m_act;    M_act.sa_sigaction = my_sigaction; M_act.sa_flags = Sa_restart |    Sa_siginfo;    Sigemptyset (&m_act.sa_mask);    Sigaddset (&m_act.sa_mask, SIGUSR1);    Sigaddset (&m_act.sa_mask, SIGUSR2);    Sigaction (SIGUSR1, &m_act, NULL);    Sigaction (SIGUSR2, &m_act, NULL); Sigaction (SIGINT, &m_act, NULL);printf("My pid is%d\n", Getpid ()); while(1);return 0;}

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Linux sigaction function (registration signal) use