在Linux中，父过程如何将PTY应用于子过程？

Question

这是父过程的代码：

#include <stdlib.h>
#include <fcntl.h>
#include <pty.h>
#include <stdio.h>
#include <utmp.h>
#include <sys/ioctl.h>
#include <unistd.h>

int main() {
    int err = 0, len = 0;
    int master, aslave;
    char name[BUFSIZ], buffer[BUFSIZ];
    FILE *child;

    err = openpty(&master, &aslave, &name[0], NULL, NULL);
    if (err == -1) {
        perror("openpty faild.");
        return EXIT_FAILURE;
    }
    fprintf(stdout, "pty name: %s\n", name);

    child = popen("./child", "r");
    if (!child) {
        perror("popen faild");
        return EXIT_FAILURE;
    }

    len = read(master, &buffer[0], BUFSIZ);
    if (len == 0) {
        fprintf(stdout, "Unable to read output from subprocess.");
        return EXIT_FAILURE;
    }
    fprintf(stdout, "child message: %s\n", buffer);
    return 0;
}

以下是子过程的代码：

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
    fprintf(stdout, "%s\n", isatty(fileno(stdout)) ? "true": "false");
    return EXIT_SUCCESS;
}

我知道，要在子过程中通过ISATTY检查，有必要通过PTY与子过程进行交互，但是需要是完毕？

尽管这可能没有应用程序方案，但我仍然想知道PTY的用法。

Answer 1

可能您可以使用posix_openpt + fork在主和从属过程之间进行互动
以下是一个例子

#include <stdlib.h>
#include <fcntl.h>
#include <pty.h>
#include <stdio.h>
#include <utmp.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <unistd.h>

int main(int argc, char* argv[]) {

  int fdMaster = 0;
  int fdSlave = 0;
  int err = 0;
  int pid = 0;


  fdMaster = posix_openpt(O_RDWR);
  if (fdMaster < 0) {
    exit(1);
  }

  err = grantpt(fdMaster);
  if (err != 0) {
    exit(1);
  }

  err = unlockpt(fdMaster);
  if (err != 0) {
    exit(1);
  }

  fdSlave = open(ptsname(fdMaster), O_RDWR);
  if (fdSlave < 0) {
    exit(1);
  }

  pid = fork();

  if (pid < 0) {
    close(fdMaster);
    exit(1);
  } else if (pid == 0) {
    // child
    close(fdMaster);
    // dup stdin, stdout & stderr
    if (dup2(fdSlave, STDIN_FILENO) != STDIN_FILENO) {
      exit(1);
    }
    if (dup2(fdSlave, STDOUT_FILENO) != STDOUT_FILENO) {
      exit(1);
    }
    if (dup2(fdSlave, STDERR_FILENO) != STDERR_FILENO) {
      exit(1);
    }
    if (-1 == execvp("./child", NULL)) {
     exit(1);
    }
  } else {
    // parent
    close(fdSlave);
    int status = 1;
    int len = 0;
    char buffer[BUFSIZ];
    wait(&status);
    len = read(fdMaster, buffer, BUFSIZ);
    if (len <= 0) {
        fprintf(stdout, "Unable to read output from subprocess.");
        return EXIT_FAILURE;
    }
    fprintf(stdout, "child message: %s\n", buffer);
    return 0;
  }
}