[ale] ptr example

[cfowler]

In case it was not obvious, the reason for the parent was so that the
ttyp0 could communicate via ptyp0 to the tty you are running the program
on.



[cfowler at cfowler tmp]$ tty
/dev/pts/7
[cfowler at cfowler tmp]$ ./pshell 
sh-2.05a$ tty
/dev/ttyp0
sh-2.05a$ exit
exit
[cfowler at cfowler tmp]$ 


On Fri, 2003-01-31 at 15:48, cfowler wrote:
> Compile with gcc -o pshell pshell.c
> 
> If ttyp0 is free, this will show you how it works.
> 
> One thing to remeber is that Linux now uses pty98 as the new standard. 
> These are pseudos found in /dev/pts.  This code supports the old names
> but it is still the same.
> 
> 
> 
> 
> #include <fcntl.h>
> #include <unistd.h>
> #include <stdio.h>
> #include <termios.h>
> #include <sys/select.h>
> 
> #define SHELL "/bin/sh"
> 
> 
> int
> main(int argc, char *argv[]) {
>         int mfd, sfd;
>         int pid;
>         fd_set fds;
>         struct termios old, new;
> 
> 
>         if((mfd = open("/dev/ptyp0", O_RDWR)) == -1) {
>                 perror("Open master");
>                 exit(1);
>         }
> 
>         if((sfd = open("/dev/ttyp0", O_RDWR)) == -1) {
>                 perror("Open slave");
>                 exit(1);
>         }
> 
>         switch(pid = fork()) {
>                 case -1:
>                         perror("fork");
>                         exit(1);
>                 case 0: // Child
>                         setsid();
>                         close(0); close(1); close(2);
>                         dup2(sfd, 0); 
>                         dup2(sfd, 1);
>                         dup2(sfd, 2);
>                         execl(SHELL, SHELL, 0);
>                         perror("exec");
>                         exit(1);
>                 default: // parent
>                         break;
> 
>         }
> 
>         close(sfd);
> 
>         // Make or terminal raw!
>         tcgetattr(1, &old);
>         new = old;
>         cfmakeraw(&new);
>         tcsetattr(1, TCSANOW, &new);
> 
>         while(1) {
>                 char b;
> 
>                 FD_ZERO(&fds);
>                 FD_SET(mfd, &fds);
>                 FD_SET(0, &fds);
> 
>                 select(mfd + 1, &fds, NULL, NULL, NULL);
> 
>                 if(FD_ISSET(mfd, &fds)) {
>                         if(read(mfd, &b, 1) <=0) {
>                                         tcsetattr(0, TCSANOW, &old);
>                                         exit(0);
>                         }
>                         write(0, &b, 1);
>                 }
> 
>                 if(FD_ISSET(0, &fds)) {
>                         read(0, &b, 1);
>                         write(mfd, &b, 1);
>                 }
>         }
>         
> 
> }
> /* vi: set ts=4 sw=4:*/
> 
> _______________________________________________
> Ale mailing list
> Ale at ale.org
> http://www.ale.org/mailman/listinfo/ale


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