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POHow do *nix pseudo-terminals work ? What's the master/slave channel?
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copied!<p>I want to write a simple, dumb, X terminal emulator in C on a Linux system. </p> <p>At first, I just thought I would have to popen a shell and display its output. I checked xterm and rxvt code, and it looks a bit more complicated.</p> <p>First, I have to open a pseudo-terminal with openpty. So I look at the man page and see that openpty fills 2 file descriptors, the master and the slave. Both xterm and rxvt code are messy because of the system-dependent-ness of those specials files.</p> <p>I understand the termios stuff : it's just a bunch of information about the escape code of the terminal. What I really don't get is : what am I suppose to do with the master/slave file descriptor ?</p> <p>An example program which open a terminal, logs in, executes a "ls" on the shell would be awesome.</p> <p><em>(English is not my native language, excuse my eventual mistake)</em></p> <p>Edit: Here's the sample code I came up with :</p> <pre><code>#include <stdlib.h> #include <stdio.h> #include <unistd.h> #include <string.h> #include <pty.h> #include <utmp.h> #include <ctype.h> void safe_print (char* s) { while(*s) { if(*s == '\n') putchar("\n"); else if(iscntrl(*s)) printf("\\e(%d)", *s); else putchar(*s); s++; } } int main (int argc, char** argv) { char buf[BUFSIZ] = {0}; int master; int ret = forkpty(&master, NULL, NULL, NULL); if(ret == -1) puts("no fork"), exit(0); if(!ret) { execl("/bin/sh", "sh", NULL); exit(0); } sleep(1); /* let the shell run */ if(argc >= 2) { write(master, argv[1], strlen(argv[1])); write(master, "\n", 1); } else { write(master, "date\n", sizeof "date\n"); } while(1) { switch(ret = read(master, buf, BUFSIZ)) { case -1: puts("error!"); exit(1); break; case 0: puts("nothing.."), sleep(1); break; default: buf[ret] = '\0'; safe_print(buf); } } close(master); return 0; } </code></pre>

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