How to use pseudo-terminals in Linux with C?

Question

I'm trying to figure out how to use pseudo-terminal's in linux, essentially I want to create a telnetd clone, something I mentioned in an earlier question.

I understand the concept of master and slave terminal, and I have a basic grasp on how to use syscalls in C.

My question concerns the next step after opening a slave / master file descriptor. How to I launch getty in the slave? Are there any good resources on the net for using the forkpty(), openpty(),or another API?

Some examples in C would help. This was a very similar question, but no one really provided any examples.

Solution 1

Advanced Programming in the Unix Environment, 2nd Edition has a superb chapter on the pseudo-terminal layer available in Linux. The best part is the source code which contains a pty driver and very clearly demonstrates how to use the pty interfaces. (The pty program it builds is useful in its own right if you want to drive a terminal-only program programmatically but don't wish to use expect(1).)

Solution 2

include

#include <sys/stat.h>

#include <fcntl.h>

#define _XOPEN_SOURCE

#include <stdlib.h>

int main(int argc, char **argv) 
{
char *slavename;
int masterfd;
masterfd = open("/dev/ptmx", O_RDWR);
grantpt(masterfd);
unlockpt(masterfd);
slavename = ptsname(masterfd);
...
}

I posted simple example of demonstrating pseudo terminal master slave concept. please go through this link to get clear understanding of terminals in Linux http://www.linusakesson.net/programming/tty/

Comments

[sarnold]

@JérémyPouyet, thanks for the notice; I've fixed the link to point to the second edition code (which is the code I'm familiar with) -- perhaps the third edition would be the better choice, but I haven't personally read that code yet. Some day. :)

[EdH]

This is the simple straightforward answer. It's documented here: linux.die.net/man/4/ptmx

[sarnold]

@CiroSantilli巴拿馬文件六四事件法轮功, sorry, I cannot find a license. Neither the second edition tarball nor the third edition tarball specify a license, the FAQs on the website do not specify a license. There is a DISCLAIMER file in the top level of the tarball which suggests it's intended to be used and useful but disclaims all liability for all consequences.

[Ciro Santilli OurBigBook.com]

Yeah, that's about what I've found too. Maybe I'll email the author, if open that has to go to GitHub :-)

[Ciro Santilli OurBigBook.com]

kerrisk's linux programming interface also has a chapter on it: github.com/cirosantilli/linux-programming-interface-kerrisk/‌​…