#include <stdio.h>
#define _XOPEN_SOURCE
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

/* my_system - synchronously spawns and waits for the command
 * "/bin/sh -c <cmd>".
 *
 * Returns -1 on error of any sort, or the exit code from the
 * launched process. Does not block or ignore any signals.
 */
int my_system(const char *);

int main(int argc, char *argv[])
{
	if (argc < 2) {
		fprintf(stderr, "usage: %s <command>", argv[0]);
		return EXIT_FAILURE;
	}

	const char *command = argv[1];
	pid_t pid = fork();
	if (pid == -1) {
		perror("fork");
		return EXIT_FAILURE;
	} else if (pid > 0) {
		int ret = my_system(command);
		if (ret == -1) {
			fprintf(stderr, "command: \"%s\" error", command);
			return EXIT_FAILURE;
		}
		return ret;
	}

	int status;
	wait(&status);
	return status;
}

int my_system(const char *cmd)
{
	pid_t pid = fork();
	if (pid == -1) {
		return -1;
	} else if (pid == 0) {
		const char *argv[4];
		argv[0] = "sh";
		argv[1] = "-c";
		argv[2] = cmd;
		argv[3] = NULL;

		execv("/bin/sh", argv);
		exit(-1);
	}

	int status;
	if (waitpid(pid, &status, 0) == -1) {
		return -1;
	} else if (WIFEXITED(status)) {
		return WEXITSTATUS(status);
	}
	return -1;
}