signal overview

来源：互联网发布：存货毕业设计数据分析编辑：程序博客网时间：2024/09/21 08:51

简要记录下signal 机制,

1. Linux 主要 signal 如下

       Signal     Value     Action   Comment
       ──────────────────────────────────────────────────────────────────────
       SIGHUP        1       Term    Hangup detected on controlling terminal
                                     or death of controlling process
       SIGINT        2       Term    Interrupt from keyboard       //CTRL + C
       SIGQUIT       3       Core    Quit from keyboard
       SIGILL        4       Core    Illegal Instruction
       SIGABRT       6       Core    Abort signal from abort(3)
       SIGFPE        8       Core    Floating point exception     //除0
       SIGKILL       9       Term    Kill signal
       SIGSEGV      11       Core    Invalid memory reference
       SIGPIPE      13       Term    Broken pipe: write to pipe with no
                                     readers
       SIGALRM      14       Term    Timer signal from alarm(2)       //alarm()
       SIGTERM      15       Term    Termination signal
       SIGUSR1   30,10,16    Term    User-defined signal 1
       SIGUSR2   31,12,17    Term    User-defined signal 2
       SIGCHLD   20,17,18    Ign     Child stopped or terminated
       SIGCONT   19,18,25    Cont    Continue if stopped

       SIGSTOP   17,19,23    Stop    Stop process
       SIGTSTP   18,20,24    Stop    Stop typed at tty
       SIGTTIN   21,21,26    Stop    tty input for background process
       SIGTTOU   22,22,27    Stop    tty output for background process

2. 主要系统调用及函数

     raise(3)        Sends a signal to the calling thread.

       kill(2)         Sends a signal to a specified process, to all members of a specified process group, or to all
                       processes on the system.

signal(2) signal - ANSI C signal handling

       SYNOPSIS
       #include <signal.h>
       typedef void (*sighandler_t)(int);
       sighandler_t signal(int signum, sighandler_t handler);

3. sample

#include <stdio.h>#include <stdlib.h>#include <sys/wait.h>#include <sys/types.h>#include <sys/unistd.h>#include <string.h>#define MAXLINE 256static void sig_int(int);static void sig_tstp(int);static void sig_fpe(int);static void sig_alrm(int);void sig_int(int signo){printf("interrupt INT %d\n%% ", signo);}void sig_tstp(int signo){printf("interrupt TSTP %d\n%% ", signo);}void sig_fpe(int signo){printf("interrupt FPE %d\n%% ", signo);}void sig_alrm(int signo){printf("interrupt ALRM %d\n%% ", signo);}int main(int argc, char* argv[]){char buf[MAXLINE];pid_tpid;int status;printf("\usage : 1. no args --> execute command\n\        2. a.out num--> 10/num, num == 0--> SIGFPE, num == 10 --> SIGINT, others --> SIGALRM\n");if(signal(SIGINT, sig_int) == SIG_ERR) {printf("signal error");}#if 0if(signal(SIGTSTP, sig_tstp) == SIG_ERR){printf("signal error");}#endifif(signal(SIGFPE, sig_fpe) == SIG_ERR){printf("signal error");}if(signal(SIGALRM, sig_alrm) == SIG_ERR){printf("signal error");}if(argc == 2){int bediv = atoi(argv[1]);int res = 10/bediv;if(res == 1){raise(SIGINT);}else if(res > 0){alarm(res);while(res){printf("%d...\n", res);res--;sleep(1); }}else{// do nothing}printf("res = %d\n", res);}printf("%% ");/* printf prompt (printf requires %% to print % )*/while(fgets(buf, MAXLINE, stdin) != NULL){buf[strlen(buf) - 1] = 0;/* replace new line with null */if((pid = fork()) < 0){printf("fork error");}else if(pid == 0)/* child */{execlp(buf, buf, (char *)0);printf("couldn't execute: %s\n", buf);exit(127);}/* parent */if((pid = waitpid(pid, &status, 0)) < 0 ){printf("waitpid error");}printf("%% ");}exit(0);}

4. demo

river@river-Satellite-L510:~/workspace/unix-adanced-programing/chapter1/signal$ ./a.out 3usage : 1. no args --> execute command        2. a.out num--> 10/num, num == 0--> SIGFPE, num == 10 --> SIGINT, others --> SIGALRM3...2...1...interrupt ALRM 14% res = 0% lsa.out  signal_demo.c% timeUsage: time [-apvV] [-f format] [-o file] [--append] [--verbose]       [--portability] [--format=format] [--output=file] [--version]       [--quiet] [--help] command [arg...]% dateFri Feb 27 23:33:37 CST 2015% ^Cinterrupt INT 2^Z[21]+  Stopped                 ./a.out 3

0 0