SIGHUP和控制进程的终止

如果因为终端断开引起的向控制进程发送的SIGHUP信号会导致控制进程终止，那么SIGHUP信号会被发送给终端的前台进程组中的成员。控制进程处于任何原因终止，那么前台进程就会收到SIGHUP信号。这个是控制进程终止的结果，不是SIGHUP信号相关联的行为。

[e-mail]:~/test/signal>more trap_sighup2.c
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>

static void handler(int sig)
{
    printf("PID %ld caught signal %2d (%s)\n",getpid(),sig,strsignal(sig));
}

int main(int argc, char *argv[])
{
    pid_t parentPid, childPid;
    int j;
    struct sigaction sa;


    if(argc < 2 || strcmp(argv[1], "--help") == 0) {
        printf("Usage: %s {d|s} ... [ > sig.log 2>&1 ]\n",argv[0]);
        return 0;
    }
    setbuf(stdout,NULL);

    parentPid = getpid();
    printf("PID of parent process is %ld,shell process id = %ld\n",(long)parentPid,getppid());
    printf("Foreground process group ID is: %ld,session id = %ld\n",(long)tcgetpgrp(STDIN_FILENO),getsid(0));

    for(j = 1; j < argc; j++) {
        childPid = fork();
        if(childPid < 0) {
            printf("fork error\n");
            return -1;
        }

        if(childPid == 0) {
            if(argv[j][0] == 'd') {
                if(setpgid(0,0) == -1) {
                    printf("setpgid error\n");
                    return -1;
                }
            }
            sigemptyset(&sa.sa_mask);
            sa.sa_flags = 0;
            sa.sa_handler = handler;
            if(sigaction(SIGHUP,&sa,NULL) == -1) {
                printf("sigaction error\n");
                return -1;
            }
            break;
        }
    }
    alarm(60);
    printf("PID = %ld,PGID = %ld\n",getpid(),getpgrp());
    for(;;)
        pause;
}

[e-mail]:~/test/signal>gcc -g trap_sighup2.c -o trap_sighup2
[e-mail]:~/test/signal>echo $$
23078
[e-mail]:~/test/signal>./trap_sighup2 d s s > trap_sighup2.log 2>&1
/*退出后重新登入*/
Last login: Thu Apr 23 17:13:20 2015 from 10.155.60.28
[e-mail]:~/codes/istanbul_4_22>
[e-mail]:~/codes/istanbul_4_22>cd ~/test/
Display all 168 possibilities? (y or n)
[e-mail]:~/codes/istanbul_4_22>cd ~/test/signal/
[e-mail]:~/test/signal>more trap_sighup2.log
PID of parent process is 23169,shell process id = 23078
Foreground process group ID is: 23169,session id = 23078
PID = 23169,PGID = 23169
PID = 23172,PGID = 23169
PID = 23171,PGID = 23169
PID = 23170,PGID = 23170
PID 23171 caught signal  1 (Hangup)
PID 23172 caught signal  1 (Hangup)