convince/sway/commands/exec_always.c

#define _XOPEN_SOURCE 500
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>
#include "sway/commands.h"
#include "sway/config.h"
#include "sway/tree/container.h"
#include "sway/tree/workspace.h"
#include "log.h"
#include "stringop.h"

struct cmd_results *cmd_exec_always(int argc, char **argv) {
	struct cmd_results *error = NULL;
	if (!config->active) return cmd_results_new(CMD_DEFER, NULL, NULL);
	if ((error = checkarg(argc, "exec_always", EXPECTED_MORE_THAN, 0))) {
		return error;
	}

	char *tmp = NULL;
	if (strcmp((char*)*argv, "--no-startup-id") == 0) {
		wlr_log(L_INFO, "exec switch '--no-startup-id' not supported, ignored.");
		if ((error = checkarg(argc - 1, "exec_always", EXPECTED_MORE_THAN, 0))) {
			return error;
		}

		tmp = join_args(argv + 1, argc - 1);
	} else {
		tmp = join_args(argv, argc);
	}

	// Put argument into cmd array
	char cmd[4096];
	strncpy(cmd, tmp, sizeof(cmd) - 1);
	cmd[sizeof(cmd) - 1] = 0;
	free(tmp);
	wlr_log(L_DEBUG, "Executing %s", cmd);

	int fd[2];
	if (pipe(fd) != 0) {
		wlr_log(L_ERROR, "Unable to create pipe for fork");
	}

	pid_t pid;
	pid_t *child = malloc(sizeof(pid_t)); // malloc'd so that Linux can avoid copying the process space
	if (!child) {
		return cmd_results_new(CMD_FAILURE, "exec_always", "Unable to allocate child pid");
	}
	// Fork process
	if ((pid = fork()) == 0) {
		// Fork child process again
		setsid();

		if ((*child = fork()) == 0) {
			// Acquire the current PATH
			char *path = getenv("PATH");
			const char *extra_path = ":/usr/lib/sway";
			const size_t extra_size = sizeof("/usr/lib/sway") + 1;

			if (!path) {
				size_t n = confstr(_CS_PATH, NULL, 0);
				path = malloc(n + extra_size);
				if (!path) {
					return cmd_results_new(CMD_FAILURE, "exec_always", "Unable to allocate PATH");
				}
				confstr(_CS_PATH, path, n);

			} else {
				size_t n = strlen(path) + 1;
				char *tmp = malloc(n + extra_size);
				if (!tmp) {
					return cmd_results_new(CMD_FAILURE, "exec_always", "Unable to allocate PATH");
				}

				strncpy(tmp, path, n);
				path = tmp;
			}

			// Append /usr/lib/sway to PATH
			strcat(path, extra_path);
			if (!setenv("PATH", path, 1)) {
				free(path);
				return cmd_results_new(CMD_FAILURE, "exec_always", "Unable to set PATH");
			}
			free(path);

			// Execute the command
			execl("/bin/sh", "/bin/sh", "-c", cmd, (void *)NULL);
			// Not reached
		}
		close(fd[0]);
		ssize_t s = 0;
		while ((size_t)s < sizeof(pid_t)) {
			s += write(fd[1], ((uint8_t *)child) + s, sizeof(pid_t) - s);
		}
		close(fd[1]);
		_exit(0); // Close child process
	} else if (pid < 0) {
		free(child);
		return cmd_results_new(CMD_FAILURE, "exec_always", "fork() failed");
	}
	close(fd[1]); // close write
	ssize_t s = 0;
	while ((size_t)s < sizeof(pid_t)) {
		s += read(fd[0], ((uint8_t *)child) + s, sizeof(pid_t) - s);
	}
	close(fd[0]);
	// cleanup child process
	wait(0);
	if (*child > 0) {
		wlr_log(L_DEBUG, "Child process created with pid %d", *child);
		// TODO: add PID to active workspace
	} else {
		free(child);
	}

	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
}