UNIX环境高级编程8.5exit 8.6wait waitpid

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#include "apue.h"
#include <sys/wait.h>

void pr_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));
}

#include "apue.h"
#include <sys/wait.h>

int
main(void)
{
	pid_t	pid;
	int		status;

	if ((pid = fork()) < 0)
		err_sys("fork error");
	else if (pid == 0)				/* child */
		exit(7);

	if (wait(&status) != pid)		/* wait for child */
		err_sys("wait error");
	pr_exit(status);				/* and print its status */

	if ((pid = fork()) < 0)
		err_sys("fork error");
	else if (pid == 0)				/* child */
		abort();					/* generates SIGABRT */

	if (wait(&status) != pid)		/* wait for child */
		err_sys("wait error");
	pr_exit(status);				/* and print its status */

	if ((pid = fork()) < 0)
		err_sys("fork error");
	else if (pid == 0)				/* child */
		status /= 0;				/* divide by 0 generates SIGFPE */

	if (wait(&status) != pid)		/* wait for child */
		err_sys("wait error");
	pr_exit(status);				/* and print its status */

	exit(0);
}

all: shell1 shell2 fork1 vfork1 wait1
shell1: shell1.c
	g++ -g -Wall shell1.c ../lib/libapue.a -I ../include -o shell1
shell2: shell2.c
	g++ -g -Wall shell2.c ../lib/libapue.a -I ../include -o shell2
fork1: fork1.c
	g++ -g -Wall fork1.c ../lib/libapue.a -I ../include -o fork1
vfork1: vfork1.c
	g++ -g -Wall vfork1.c ../lib/libapue.a -I ../include -o vfork1
wait1: wait1.c
	g++ -g -Wall wait1.c ../lib/libapue.a -I ../include -o wait1
clean:
	rm shell1 shell2 fork1 vfork1 wait1

调用fork两次以避免僵死进程

#include "apue.h"
#include <sys/wait.h>

int main(void)
{
    printf("file %s, line %d parent, getpid() = %d\n", __FILE__, __LINE__, getpid());
    fflush(stdout);
    pid_t pid;

    if ((pid = fork()) < 0)
    {
        err_sys("fork error");
    }
    else if (pid == 0)
    { /* first child */
        printf("file %s, line %d child 1, getpid() = %d\n", __FILE__, __LINE__, getpid());
        fflush(stdout);
        if ((pid = fork()) < 0)
        {
            err_sys("fork error");
        }
        else if (pid > 0)
        {
            printf("first child, going to sleep(2)\n");
            sleep(2);
            printf("first child, after sleep(2), begin exiting\n");
            exit(0);   /* parent from second fork == first child */
        }

        /*
         * We‘re the second child; our parent becomes init as soon
         * as our real parent calls exit() in the statement above.
         * Here‘s where we‘d continue executing, knowing that when
         * we‘re done, init will reap our status.
         */
        printf("file %s, line %d, child 2, getpid() = %d\n", __FILE__, __LINE__, getpid());
        printf("second child, going to sleep(5)\n");
        sleep(5);
        printf("second child, after sleep(5)\n");
        printf("second child, parent pid = %d, parent id is 1, which means my parent process is init\n", getppid());
        exit(0);
    }

    if (waitpid(pid, NULL, 0) != pid)  /* wait for first child */
        err_sys("waitpid error");
    else
        printf("after sleep(2), first child exit caught by parent (waitpid)\n");

    printf("file %s, line %d, getpid() = %d\n", __FILE__, __LINE__, getpid());

    /*
     * We‘re the parent (the original process); we continue executing,
     * knowing that we‘re not the parent of the second child.
     */
    exit(0);
}

all: shell1 shell2 fork1 vfork1 wait1 fork2
shell1: shell1.c
	g++ -g -Wall shell1.c ../lib/libapue.a -I ../include -o shell1
shell2: shell2.c
	g++ -g -Wall shell2.c ../lib/libapue.a -I ../include -o shell2
fork1: fork1.c
	g++ -g -Wall fork1.c ../lib/libapue.a -I ../include -o fork1
fork2: fork2.c
	g++ -g -Wall fork2.c ../lib/libapue.a -I ../include -o fork2
vfork1: vfork1.c
	g++ -g -Wall vfork1.c ../lib/libapue.a -I ../include -o vfork1
wait1: wait1.c
	g++ -g -Wall wait1.c ../lib/libapue.a -I ../include -o wait1
clean:
	rm shell1 shell2 fork1 vfork1 wait1 fork2

UNIX环境高级编程8.5exit 8.6wait waitpid

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原文地址：http://www.cnblogs.com/sunyongjie1984/p/4262982.html