open.c

unix环境高级编程的源代码

#include    "open.h"
#include    <sys/uio.h>        /* struct iovec */

/* Open the file by sending the "name" and "oflag" to the
 * connection server and reading a file descriptor back. */

int
csopen(char *name, int oflag)
{
    pid_t            pid;
    int                len;
    char            buf[10];
    struct iovec    iov[3];
    static int        fd[2] = { -1, -1 };

    if (fd[0] < 0) {    /* fork/exec our open server first time */
        if (s_pipe(fd) < 0)
            err_sys("s_pipe error");
        if ( (pid = fork()) < 0)
            err_sys("fork error");
        else if (pid == 0) {        /* child */
            close(fd[0]);
            if (fd[1] != STDIN_FILENO) {
                if (dup2(fd[1], STDIN_FILENO) != STDIN_FILENO)
                    err_sys("dup2 error to stdin");
            }
            if (fd[1] != STDOUT_FILENO) {
                if (dup2(fd[1], STDOUT_FILENO) != STDOUT_FILENO)
                    err_sys("dup2 error to stdout");
            }
            if (execl("./opend", "opend", NULL) < 0)
                err_sys("execl error");
        }
        close(fd[1]);                /* parent */
    }

    sprintf(buf, " %d", oflag);        /* oflag to ascii */
    iov[0].iov_base = CL_OPEN " ";
    iov[0].iov_len  = strlen(CL_OPEN) + 1;
    iov[1].iov_base = name;
    iov[1].iov_len  = strlen(name);
    iov[2].iov_base = buf;
    iov[2].iov_len  = strlen(buf) + 1;    /* +1 for null at end of buf */
    len = iov[0].iov_len + iov[1].iov_len + iov[2].iov_len;
    if (writev(fd[0], &iov[0], 3) != len)
        err_sys("writev error");

            /* read descriptor, returned errors handled by write() */
    return( recv_fd(fd[0], write) );
}