image.png

/*
 * An example of pseudo terminal
 */

#define _GNU_SOURCE
#include <stdlib.h>   //xxxpt()
#include <fcntl.h>    //O_RDWR
#include <stdio.h>    //fprintf()
#include <errno.h>    //perror(),errno
#include <unistd.h>   //read(),write(),fork(),open(),close()
#include <termios.h>


int main(void)
{
    int fdm, fds, rc;
    char input[150];

    fdm = posix_openpt(O_RDWR);
    if (fdm < 0) {
        perror("when posix_openpt() pty-master");
        return 1;
    }

    rc = unlockpt(fdm);
    if (rc != 0) {
        perror("when unlockpt() pty-master");
        return 1;
    }

    fds = open(ptsname(fdm), O_RDWR);
    if (fds < 0) {
        perror("when open() pty-slave");
        return 1;
    }

    if (fork()) { // Father
        close(fds);

        while (1) {
            write(1, "Input : ", sizeof("Input : "));
            rc = read(0, input, sizeof(input)-1);
            if (rc > 0) {
                write(fdm, input, rc);

                rc = read(fdm, input, sizeof(input)-1);
                if (rc > 0) {
                    fprintf(stdout, "111-%s", input);
                }
                else
                    break;
            }
            else
                break;
        }
    }
    else { // Child
        close(fdm);

        struct termios settings;
        rc = tcgetattr(fds, &settings);
        cfmakeraw (&settings);
        tcsetattr (fds, TCSANOW, &settings);

        dup2(fds, 0);
        dup2(fds, 1);
        dup2(fds, 2);

        while (1)
        {
           rc = read(0, input, sizeof(input) - 1);
           if (rc > 0) {
               input[rc - 1] = '\0';
               fprintf(stdout, "222-%s\n", input);
           }
           else
               break;
        }
    }

    return 0;
}

$ gcc a.c && ./a.out
Input : aaa
111-222-aaa
Input : bbb
111-222-bbb

参考

http://rachid.koucha.free.fr/tech_corner/pty_pdip.html