APUE Chapter 9.Process Relationships 后台任务设为前台任务的后果

结论: 对于支持job control的环境, 后台任务设置为前台任务的后果就是，该后台任务变为前台任务，执行结束后，Terminal自行退出。

测试代码：

#include <stdio.h>#include <fcntl.h>#include <unistd.h>#include <sys/wait.h>#include "apue.h"#include <errno.h>#include <signal.h>static voidsig_tou(int signo){    printf("SIGTTOU received, pid = %ld\n", (long)getpid());}static voidsig_tin(int signo){    printf("SIGTTIN received, pid = %ld\n", (long)getpid());}static voidsig_int(int signo){    printf("SIGTINT received, pid = %ld\n", (long)getpid());}void pr_exit(int status);int main(){    int pid;    int state;    int fd;    if((fd = open("/dev/tty", O_RDWR))<0)        err_sys("no terminal");    signal(SIGTTOU, SIG_IGN);    signal(SIGTTIN, sig_tin);    signal(SIGINT, sig_int);    if((pid = fork()) == 0)    {    setpgid(0,getpid());    while(tcsetpgrp(fd,getpid())<0){        printf("child:%s\n", strerror(errno));        if(errno == EINTR )            continue;        else            err_sys("child set fail");    }    printf("After tcsetpgrp,the fore process group is %d\n",(int)tcgetpgrp(0));    printf("I am child,process id is %d,process group id is %d\n",getpid(),getpgrp());    exit(6);    }    else    {        setpgid(pid,pid);        while(tcsetpgrp(fd,pid)<0){            if(errno == EINTR )                continue;            else                exit(1);        }        //printf("I am father,process id is %d,process group id is %d\n",getpid(),getpgrp());        //printf("in father perspective,the fore process group is %d\n",(int)tcgetpgrp(0));        while(waitpid(pid, &state, WNOHANG) != pid){}        pr_exit(state);    }    return 0;}voidpr_exit(int status){    if (WIFEXITED(status))        printf("normal termination, exit status = %d\n", WEXITSTATUS(status));    else if (WIFSIGNALED(status))        printf("abnormal termination, signal number = %d%s\n",                WTERMSIG(status),#ifdef  WCOREDUMP                WCOREDUMP(status) ? " (core file generated)" : "");#else        "");#endif    else if (WIFSTOPPED(status))        printf("child stopped, signal number = %d\n", WSTOPSIG(status));}

MacOSX 13.4.0 本地运行结果:

$ gcc prog.c libapue.a;
$ ./a.out&
[1] 29190
$ After tcsetpgrp,the fore process group is 29191
I am child,process id is 29191,process group id is 29191
normal termination, exit status = 6
logout

[Process completed]