Linux 伪终端demo

terminal_emulator_demo.c

#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>

#define BUFSIZE 1024

int main()
{
    int ptm,sfd;
    char *slavedevice;
    if((ptm = open("/dev/ptmx", O_RDWR)) == -1)
    {
     perror("posix_openpt() error");
     exit(-1);
    }
    fcntl(ptm, F_SETFD, FD_CLOEXEC);
    if(grantpt(ptm) == -1)
    {
     perror("grantpt() error");
     exit(-1);
    }
    if(unlockpt(ptm) == -1)
    {
     perror("unlockpt() error");
     exit(-1);
    }
    if((slavedevice=ptsname(ptm)) == NULL)
    {
     perror("ptsname() error");
     exit(-1);
    }
    int pid = fork();
    if( pid == 0 ) {

        close(ptm);
        setsid();

        int pts = open(slavedevice, O_RDWR);

        if(pts < 0) exit(-1);
        dup2(pts, 0);
        dup2(pts, 1);
        dup2(pts, 2);

        execv("/bin/sh",NULL);
        exit(0);
    }
    
    int nread;
    char buf[BUFSIZE];
    if( fork() == 0 ){
        
        for(;;)
        {
        if( (nread=read(STDIN_FILENO,buf,BUFSIZE)) < 0 ){
                perror("read");
                break;
            }
            else if( nread == 0 )
                break;
            if( write(ptm,buf,nread) != nread ){
                perror("write");
                break;
            }
        }
    } else {
        for(;;)
        {
            if( (nread = read(ptm,buf,BUFSIZE) ) <0 )
                break;
            if( write (STDOUT_FILENO,buf,nread) != nread ){
                perror("write");
                break;
            }
        }
    }
    close(ptm);
    
    return 0;
}