pts

pts.c (3821B)

// SPDX-FileCopyrightText: 2017 Haelwenn (lanodan) Monnier <contact+utils-pts@hacktivis.me>
// SPDX-License-Identifier: MIT
#define _POSIX_C_SOURCE 200809L
#define _XOPEN_SOURCE 800
#include <stdlib.h> // posix_openpt, ptsname
#include <fcntl.h> // O_*
#include <string.h> // strerror
#include <stdio.h> // fprintf, perror
#include <errno.h>
#include <poll.h>
#include <unistd.h> // execvp, dup2
#include <sys/wait.h>
#include <signal.h>
static int child_status = 0;
static pid_t pid = -1;
static void
handle_sigchld(int sig)
{
	(void)sig;
	waitpid(pid, &child_status, WNOHANG);
	exit(WEXITSTATUS(child_status));
}
int
main(int argc, char *argv[])
{
	argc--;
	argv++;
	if(argc < 1)
	{
		fprintf(stderr, "pts: Expected >= 1 arguments, got %d\n", argc);
		return 1;
	}
	int manager = posix_openpt(O_RDWR|O_NOCTTY);
	if(manager < 0)
	{
		fprintf(stderr, "pts: Failed opening pseudo-terminal: %s\n", strerror(errno));
		return 1;
	}
	if(grantpt(manager) < 0)
	{
		perror("pts: Error in grantpt(manager)");
		return 1;
	}
	if(unlockpt(manager) < 0)
	{
		perror("pts: Error in unlockpt(manager)");
		return 1;
	}
	pid = fork();
	if(pid < 0)
	{
		fprintf(stderr, "pts: Fork failed: %s\n", strerror(errno));
		return 1;
	}
	if(pid != 0)
	{
		nfds_t nfds = 2;
		struct pollfd pfds[2] = {
			{
				.fd = manager,
				.events = POLLIN
			},
			{
				.fd = STDIN_FILENO,
				.events = POLLIN
			}
		};
		if(signal(SIGCHLD, handle_sigchld) == SIG_ERR)
		{
			fprintf(stderr, "timeout: Failed registering handler for SIGCHLD: %s\n", strerror(errno));
			return 1;
		}
		// parent
		do {
			int ret = poll(pfds, nfds, -1);
			if(ret < 0)
			{
				fprintf(stderr, "pts: Poll failed: %s\n", strerror(errno));
				return 1;
			}
			if(ret == 0) continue; // timeout
			if(pfds[0].revents & POLLIN)
			{
				char buf[BUFSIZ] = "";
				ssize_t nread = read(pfds[0].fd, buf, BUFSIZ);
				if(nread < 0)
				{
					fprintf(stderr, "pts: Failed reading from pseudo-terminal: %s\n", strerror(errno));
					return 1;
				}
				if(nread == 0) break;
				if(write(STDOUT_FILENO, buf, nread) < 0)
				{
					fprintf(stderr, "pts: Failed writing pseudo-terminal content to stdout: %s\n", strerror(errno));
					return 1;
				}
			}
			if(pfds[1].revents & POLLIN)
			{
				char buf[BUFSIZ] = "";
				ssize_t nread = read(pfds[1].fd, buf, BUFSIZ);
				if(nread < 0)
				{
					fprintf(stderr, "pts: Failed reading from stdin: %s\n", strerror(errno));
					return 1;
				}
				if(nread == 0) break;
				if(write(manager, buf, nread) < 0)
				{
					fprintf(stderr, "pts: Failed writing stdin content to pseudo-terminal: %s\n", strerror(errno));
					return 1;
				}
			}
			if(waitpid(pid, &child_status, WNOHANG) < 0)
			{
				fprintf(stderr, "pts: Failed getting status for child process: %s\n", strerror(errno));
				return 1;
			}
		} while(child_status == 0 || !WIFEXITED(child_status));
		return WEXITSTATUS(child_status);
	}
	else
	{
		// child
		char *name = ptsname(manager);
		int sub = open(name, O_RDWR|O_NOCTTY);
		if(sub < 0)
		{
			fprintf(stderr, "pts: Failed opening subsidiary pseudo-terminal at '%s': %s\n", name, strerror(errno));
			return 1;
		}
		if(dup2(sub, STDIN_FILENO) < 0)
		{
			fprintf(stderr, "pts: Failed assigning subsidiary pseudo-terminal to stdin: %s\n", strerror(errno));
			return 1;
		}
		if(dup2(sub, STDOUT_FILENO) < 0)
		{
			fprintf(stderr, "pts: Failed assigning subsidiary pseudo-terminal to stdout: %s\n", strerror(errno));
			return 1;
		}
		if(dup2(sub, STDERR_FILENO) < 0)
		{
			fprintf(stderr, "pts: Failed assigning subsidiary pseudo-terminal to stderr: %s\n", strerror(errno));
			return 1;
		}
		if(execvp(argv[0], argv) < 0)
		{
			fprintf(stderr, "pts: Failed to execute '%s': %s\n", argv[0], strerror(errno));
			return errno == ENOENT ? 127 : 126;
		}
		abort();
	}
}