pipe4.c

unix环境高级编程的源代码

#include    <signal.h>
#include    "ourhdr.h"

static void    sig_pipe(int);        /* our signal handler */

int
main(void)
{
    int        n, fd1[2], fd2[2];
    pid_t    pid;
    char    line[MAXLINE];

    if (signal(SIGPIPE, sig_pipe) == SIG_ERR)
        err_sys("signal error");

    if (pipe(fd1) < 0 || pipe(fd2) < 0)
        err_sys("pipe error");

    if ( (pid = fork()) < 0)
        err_sys("fork error");
    else if (pid > 0) {                            /* parent */
        close(fd1[0]);
        close(fd2[1]);
        while (fgets(line, MAXLINE, stdin) != NULL) {
            n = strlen(line);
            if (write(fd1[1], line, n) != n)
                err_sys("write error to pipe");
            if ( (n = read(fd2[0], line, MAXLINE)) < 0)
                err_sys("read error from pipe");
            if (n == 0) {
                err_msg("child closed pipe");
                break;
            }
            line[n] = 0;    /* null terminate */
            if (fputs(line, stdout) == EOF)
                err_sys("fputs error");
        }
        if (ferror(stdin))
            err_sys("fgets error on stdin");
        exit(0);

    } else {                                    /* child */
        close(fd1[1]);
        close(fd2[0]);
        if (fd1[0] != STDIN_FILENO) {
            if (dup2(fd1[0], STDIN_FILENO) != STDIN_FILENO)
                err_sys("dup2 error to stdin");
            close(fd1[0]);
        }
        if (fd2[1] != STDOUT_FILENO) {
            if (dup2(fd2[1], STDOUT_FILENO) != STDOUT_FILENO)
                err_sys("dup2 error to stdout");
            close(fd2[1]);
        }
        if (execl("./add2", "add2", (char *) 0) < 0)
            err_sys("execl error");
    }
}

static void
sig_pipe(int signo)
{
    printf("SIGPIPE caught\n");
    exit(1);
}