loop.c

unix环境高级编程的源代码

#include    <sys/types.h>
#include    <signal.h>
#include    "ourhdr.h"

#define    BUFFSIZE    512

static void    sig_term(int);
static volatile sig_atomic_t    sigcaught;    /* set by signal handler */

void
loop(int ptym, int ignoreeof)
{
    pid_t    child;
    int        nread;
    char    buff[BUFFSIZE];
    if ( (child = fork()) < 0) {
        err_sys("fork error");

    } else if (child == 0) {    /* child copies stdin to ptym */
        for ( ; ; ) {
            if ( (nread = read(STDIN_FILENO, buff, BUFFSIZE)) < 0)
                err_sys("read error from stdin");
            else if (nread == 0)
                break;        /* EOF on stdin means we're done */

            if (writen(ptym, buff, nread) != nread)
                err_sys("writen error to master pty");
        }

            /* We always terminate when we encounter an EOF on stdin,
               but we only notify the parent if ignoreeof is 0. */
        if (ignoreeof == 0)
            kill(getppid(), SIGTERM);    /* notify parent */
        exit(0);    /* and terminate; child can't return */
    }

        /* parent copies ptym to stdout */
    if (signal_intr(SIGTERM, sig_term) == SIG_ERR)
        err_sys("signal_intr error for SIGTERM");

    for ( ; ; ) {
        if ( (nread = read(ptym, buff, BUFFSIZE)) <= 0)
            break;        /* signal caught, error, or EOF */

        if (writen(STDOUT_FILENO, buff, nread) != nread)
            err_sys("writen error to stdout");
    }

    /* There are three ways to get here: sig_term() below caught the
     * SIGTERM from the child, we read an EOF on the pty master (which
     * means we have to signal the child to stop), or an error. */

    if (sigcaught == 0)    /* tell child if it didn't send us the signal */
        kill(child, SIGTERM);
    return;        /* parent returns to caller */
}

/* The child sends us a SIGTERM when it receives an EOF on
 * the pty slave or encounters a read() error. */

static void
sig_term(int signo)
{
    sigcaught = 1;        /* just set flag and return */
    return;                /* probably interrupts read() of ptym */
}