Programming

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/time.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <signal.h>
#include <stdio.h>
#include <errno.h>
#include <sys/ioctl.h>

#ifndef TIOCNOTTY
#include <termios.h>
#endif

static char pty_name[12];

int pty_master();
int pty_slave();
int reaper;

void handler(i)
int i;
{
	if (i==
#ifdef SIGCHLD
		SIGCHLD
#else
		SIGCLD
#endif
		)
	{
/*		reaper++;*/
	}	
}

int main(argc,argv)
int argc;
char **argv;
{
	int master=-1;
	int fd=-1;
	int pid=-1;
	int pipes[2];

	pipe(pipes);
	
	master=pty_master();

	if (master < 0) return 1;

/* disconnect */


/*	if (setpgrp(getpid(),getpid()) < 0)
	{
		perror("setpgrp");
		return 1;
	}
*/
/*	if (setsid()==-1)
	{
		perror("setsid");
		return 1;
	}
*/
/* end disconnect */	

/*	if (ioctl(master,TIOCSCTTY,NULL))
	{
		perror("TIOCSCTTY master initial");
	}
*/
	pid=fork();

	if (pid)
	{
		int status=0;
		char buf[1];
		/* master */
		buf[0]=0;
		close(pipes[1]);
		read(pipes[0],buf,sizeof(buf));
		close(pipes[0]);

		if (buf[0]==0)
		{
			printf("child reported error\n");
			return 1;
		}

#ifdef SIGCHLD
		signal(SIGCHLD,handler);
#else
		signal(SIGCLD,handler);
#endif

		while (!reaper)
		{
			fd_set fds;

			FD_ZERO(&fds);
			FD_SET(master,&fds);
			FD_SET(0,&fds);

			if (select(master+1,&fds,NULL,NULL,NULL) > 0)
			{
				if (FD_ISSET(master,&fds))
				{
					char buf[256];
					int i=read(master,buf,sizeof(buf));
					if (i > 0)
					{
						write(1,buf,i);
					}
					else
					{
						i=errno;
						break;
					}
				}

				if (FD_ISSET(0,&fds))
				{
					char buf[256];
					int i=read(0,buf,sizeof(buf));
					if (i > 0)
					{
						write(master,buf,i);
					}
					else
					{
						kill(pid,SIGHUP);
						break;
					}
				}
			}
		}

		printf("out of loop, reaper=%d\n",reaper);

		kill(pid,SIGTERM);
	}
	else
	{
		/* child */
		int slave;

/*		signal(SIGHUP,handler);
		signal(SIGTERM,handler);
		signal(SIGINT,handler);
*/
		fd=open("/dev/tty",O_RDWR);

		if (fd >= 0)
		{
			if (ioctl(fd,TIOCNOTTY,(char *)0) < 0)
			{
				perror("TIOCNOTTY /dev/tty");
			}

			close(fd);
		}
		else
		{
			perror("/dev/tty");
		}

		if (setsid() < 0)
		{
			perror("setsid");
		}

		slave=pty_slave(master);

		if (slave < 0) 
		{
			perror("pty_slave");
			return 1;
		}

/*		if (setsid()==-1)
		{
			perror("setsid(2)");
		}
*/
		if (ioctl(slave,TIOCSCTTY,NULL))
		{
			perror("slave TIOCSCTTY");
			if (ioctl(master,TIOCSCTTY,NULL))
			{
				perror("master TIOCSCTTY");
			}
		}

		{
			pid_t grp=getpgrp();
			if (ioctl(master,TIOCSPGRP,&grp))
			{
				perror("TIOCSPGRP master");
			}
			if (ioctl(slave,TIOCSPGRP,&grp))
			{
				perror("TIOCSPGRP slave");
			}
		}

		if (dup2(slave,0)==-1) { perror("dup 0") ; return 1; }
		if (dup2(slave,2)==-1) { perror("dup 2") ; return 1; }
		if (dup2(slave,1)==-1) { perror("dup 1"); return 1; }

		close(slave); 
		close(master);

		printf("[%d] on %s\n",getpid(),ttyname(0));

		fflush(stdout);

		fd=open("/dev/tty",O_RDWR);

		if (fd >= 0)
		{
			close(fd);
		}
		else
		{
			perror("open /dev/tty for TIOCSPGRP");
			return 1;
		}

		write(pipes[1],"1",1);

		close(pipes[0]);
		close(pipes[1]);

		if (argc==1)
		{
			char *argv2[2];
			char *p=getenv("SHELL");
			if (!p) p="/bin/sh";
			argv2[0]=p;
			argv2[1]=NULL;
			execvp(p,argv2);
			printf("exec(%s) failed\n",p);
			return 1;
		}
		else
		{
			execvp(argv[1],argv+1);
			printf("exec(%s) failed\n",argv[1]);
			return 1;
		}
	}

	return 0;
}


int pty_master()
{
	int i,master_fd=-1;
	char *ptr;
	struct stat statbuff;
	static char ptychar[]="pqrs";
	static char hexdigit[]="0123456789abcdef";

	for (ptr=ptychar; *ptr!=0; ptr++)
	{
		strcpy(pty_name,"/dev/ptyXY");
		pty_name[8]=*ptr;
		pty_name[9]='0';

		if (stat(pty_name,&statbuff) < 0) break;

		for (i=0;i<16;i++)
		{
			pty_name[9]=hexdigit[i];
			if ((master_fd=open(pty_name,O_RDWR))>=0)
			{
				return master_fd;
			}
		}
	}

	return master_fd;
}

int pty_slave(master_fd)
int master_fd;
{
	int slave_fd=-1;

	pty_name[5]='t';

	printf("pty_slave(%s)\n",pty_name);

	if ((slave_fd=open(pty_name,O_RDWR))<0)
	{
		close(master_fd);
		return -1;
	}

	return slave_fd;
}