42Bangkok Exam Rank04

microshell.c

#include <string.h>
#include <unistd.h>
#include <sys/wait.h>

static void perr(char *s) {
	while (*s)
		write(2, s++, 1);
}

static int cd(char **argv, int i) {
	if (i != 2)
		return (perr("error: cd: bad arguments\n"), 1);
	else if (chdir(argv[1]) == -1)
		return (perr("error: cd: cannot change directory to "), perr(argv[1]), perr("\n"), 1);
	return 0;
}

static int exec(char **argv, char **envp, int i) {
	int status;
	int fds[2];
	int pip = (argv[i] && !strcmp(argv[i], "|"));
	if (pip && pipe(fds) == -1)
		return (perr("error: fatal\n"), 1);
	int pid = fork();
	if (!pid) {
		argv[i] = 0;
		if (pip && (dup2(fds[1], 1) == -1 || close(fds[0]) == -1 || close(fds[1]) == -1))
			return (perr("error: fatal\n"), 1);
		execve(*argv, argv, envp);
		return (perr("error: cannot execute "), perr(*argv), perr("\n"), 1);
	}
	waitpid(pid, &status, 0);
	if (pip && (dup2(fds[0], 0) == -1 || close(fds[0]) == -1 || close(fds[1]) == -1))
		return (perr("error: fatal\n"), 1);
	return WIFEXITED(status) && WEXITSTATUS(status);
}

int main(int argc, char **argv, char **envp) {
	(void) argc;
	int status = 0;
	while(*argv && *(argv + 1)) {
		argv++;
		int i = 0;
		while (argv[i] && strcmp(argv[i], "|") && strcmp(argv[i], ";"))
			i++;		
		if (!strcmp(*argv, "cd"))
			status = cd(argv, i);
		else if (i)
			status = exec(argv, envp, i);
		argv += i;
	}
	return (status);
}

microshell_full.c

#include <string.h>
#include <unistd.h>
#include <sys/wait.h>

int fd;

static void perr(char *s) {
	while (*s)
		write(2, s++, 1);
}

static int cd(char **argv, int i) {
	if (i != 2)
		return (perr("error: cd: bad arguments\n"), 1);
	else if (chdir(argv[1]) == -1)
		return (perr("error: cd: cannot change directory to "), perr(argv[1]), perr("\n"), 1);
	return 0;
}

static int exec(char **argv, char **envp, int i) {
	int status;
	int fds[2];
	int pip = (argv[i] && !strcmp(argv[i], "|"));
	if (pip && pipe(fds) == -1)
		return (perr("error: fatal\n"), 1);
	int pid = fork();
	if (!pid) {
		argv[i] = 0;
		if (dup2(fd, 0) == -1 || close(fd) == -1)
			return (perr("error: fatal\n"), 1);
		if (pip && (dup2(fds[1], 1) == -1 || close(fds[0]) == -1 || close(fds[1]) == -1))
			return (perr("error: fatal\n"), 1);
		execve(*argv, argv, envp);
		return (perr("error: cannot execute "), perr(*argv), perr("\n"), 1);
	}
	waitpid(pid, &status, 0);
	if (!pip && dup2(0, fd) == -1)
		return (perr("error: fatal\n"), 1);
	if (pip && (dup2(fds[0], fd) == -1 || close(fds[0]) == -1 || close(fds[1]) == -1))
		return (perr("error: fatal\n"), 1);
	return WIFEXITED(status) && WEXITSTATUS(status);
}

int main(int argc, char **argv, char **envp) {
	(void) argc;
	int status = 0;
	fd = dup(0);
	while(*argv && *(argv + 1)) {
		argv++;
		int i = 0;
		while (argv[i] && strcmp(argv[i], "|") && strcmp(argv[i], ";"))
			i++;		
		if (!strcmp(*argv, "cd"))
			status = cd(argv, i);
		else if (i)
			status = exec(argv, envp, i);
		argv += i;
	}
	if (dup2(0, fd) == -1)
		perr("error: fatal\n");
	return (status);
}