bravegnu · July 27, 2016 11:04
diff --git a/mshell.c b/mshell.c
 #define _GNU_SOURCE
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 #include <assert.h>
 #include <ctype.h>

 /*
 * Trims lead and trailing whitespace, in a string. Returns the
 * pointer that points to an offset within the string. The original
 * string is modified in-place, to trim the trailing whitespace.
 *
 * Derived from http://stackoverflow.com/a/122721/1295013
 */
 char *trim(char *str)
 {
 	char *end;

 	/* Trim leading space. */
 	while (isspace(*str))
 		str++;

 	if (*str == 0)  /* All spaces? */
 		return str;

 	/* Trim trailing space. */
 	end = str + strlen(str) - 1;
 	while (end > str && isspace(*end))
 		end--;

 	/* Write new null terminator. */
 	*(end + 1) = 0;

 	return str;
 }

 /*
 * Split a string, using the specified delimiter. Returns a array of
 * pointers, to offsets within the provided string. The array of
 * pointers is dynamically allocated. The original string is modified
 * in-place, to insert nul characters to terminate each sub-string.
 *
 * Dervied from http://stackoverflow.com/a/9210560/1295013
 */
 char **str_split(char *str, const char delim_ch)
 {
 	char **result = 0;
 	size_t count = 0;
 	char *tmp = str;
 	char *last_comma = 0;
 	char delim[2];

 	delim[0] = delim_ch;
 	delim[1] = 0;

 	/* Count how many elements will be extracted. */
 	while (*tmp) {
 		if (delim_ch == *tmp) {
 			count++;
 			last_comma = tmp;
 		}
 		tmp++;
 	}

 	/* Add space for trailing token. */
 	count += last_comma < (str + strlen(str) - 1);

 	/* Add space for terminating null string so caller
 	   knows where the list of returned strings ends. */
 	count++;

 	result = malloc(sizeof(char *) * count);

 	if (result) {
 		size_t idx = 0;
 		char *token = strtok(str, delim);

 		while (token) {
 			assert(idx < count);
 			*(result + idx++) = strdup(token);
 			token = strtok(0, delim);
 		}
 		assert(idx == count - 1);
 		*(result + idx) = 0;
 	}

 	return result;
 }

 /*
 * Input directory from user, and change current working directory to
 * the user specified directory.
 */
 void do_chdir(void)
 {
 	char *line = NULL;
 	size_t len = 0;
 	ssize_t ret;
 	int err;
 	char *dirname;

 	printf("dir: ");

 	ret = getline(&line, &len, stdin);
 	if (ret == -1) {
 		fprintf(stderr, "error reading input\n");
 		return;
 	}

 	dirname = trim(line);

 	err = chdir(dirname);
 	if (err == -1) {
 		fprintf(stderr, "chdir failed: %s\n", strerror(errno));
 		goto err_exit;
 	}

 err_exit:
 	free(line);
 }

 /*
 * Input command from user, and execute the command in the foreground.
 */
 void do_exec_cmd(void)
 {
 	char *line = NULL;
 	size_t len = 0;
 	ssize_t ret;
 	pid_t cpid;
 	int err;
 	char **split;
 	char *trimed;

 	printf("cmd: ");

 	ret = getline(&line, &len, stdin);
 	if (ret == -1) {
 		fprintf(stderr, "error reading input\n");
 		return;
 	}

 	trimed = trim(line);
 	if (strlen(trimed) == 0)
 		goto err_free_line;

 	split = str_split(trimed, ' ');
 	if (split == NULL) {
 		fprintf(stderr, "error splitting command\n");
 		goto err_free_line;
 	}

 	cpid = fork();
 	if (cpid == -1) {
 		fprintf(stderr, "error creating child: %s\n", strerror(errno));
 		goto err_free_split;
 	}

 	if (cpid == 0) {
 		execvp(split[0], split);
 		fprintf(stderr, "error executing cmd '%s': %s\n",
 			split[0], strerror(errno));
 		exit(0);
 	}

 	err = waitpid(cpid, NULL, 0);
 	if (err == -1) {
 		if (errno != ECHILD)
 			fprintf(stderr, "error waiting for child: %s\n",
 				strerror(errno));
 		goto err_free_split;
 	}

 err_free_split:
 	free(split);

 err_free_line:
 	free(line);
 }

 void show_help(char *menu[])
 {
 	int i;

 	for (i = 0; menu[i] != NULL; i++)
 		printf("%s\n", menu[i]);
 }

 /*
 * Print a prompt to the user to select a menu item. If user specifies
 * an invalid option displays the menu.
 */
 int do_prompt(char *menu[])
 {
 	int i;
 	char line[8];
 	char *retp;

 	while (1) {
 		char *cwd;

 		cwd = get_current_dir_name();
 		if (cwd == NULL)
 			cwd = "(none)";

 		printf("%s$ ", cwd);
 		free(cwd);

 		retp = fgets(line, sizeof(line), stdin);
 		if (retp == NULL)
 			return EOF;

 		for (i = 0; menu[i] != NULL; i++) {
 			if (line[0] == menu[i][0])
 				return line[0];
 		}

 		fprintf(stderr, "unrecognized input: %c\n", line[0]);
 		show_help(menu);
 	}

 	return 0;
 }

 /*
 * Main application entry point.
 */
 int main(int argc, char *argv[])
 {
 	char *main_menu[] = {
 		"c: Change Directory",
 		"f: Execute Command",
 		"x: Exit",
 		"h: Help",
 		NULL,
 	};


 	while (1) {
 		int cmd = do_prompt(main_menu);

 		switch (cmd) {
 		case 'c':
 			do_chdir();
 			break;
 		case 'f':
 			do_exec_cmd();
 			break;
 		case 'h':
 			show_help(main_menu);
 			break;
 		case 'x':
 		case EOF:
 			return 0;
 		}
 	}
 }
	#define _GNU_SOURCE
	#include <sys/types.h>
	#include <sys/wait.h>
	#include <unistd.h>

	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <errno.h>
	#include <assert.h>
	#include <ctype.h>

	/*
	* Trims lead and trailing whitespace, in a string. Returns the
	* pointer that points to an offset within the string. The original
	* string is modified in-place, to trim the trailing whitespace.
	*
	* Derived from http://stackoverflow.com/a/122721/1295013
	*/
	char trim(char str)
	{
	char *end;

	/* Trim leading space. */
	while (isspace(*str))
	str++;

	if (str == 0) / All spaces? */
	return str;

	/* Trim trailing space. */
	end = str + strlen(str) - 1;
	while (end > str && isspace(*end))
	end--;

	/* Write new null terminator. */
	*(end + 1) = 0;

	return str;
	}

	/*
	* Split a string, using the specified delimiter. Returns a array of
	* pointers, to offsets within the provided string. The array of
	* pointers is dynamically allocated. The original string is modified
	* in-place, to insert nul characters to terminate each sub-string.
	*
	* Dervied from http://stackoverflow.com/a/9210560/1295013
	*/
	char *str_split(char str, const char delim_ch)
	{
	char **result = 0;
	size_t count = 0;
	char *tmp = str;
	char *last_comma = 0;
	char delim[2];

	delim[0] = delim_ch;
	delim[1] = 0;

	/* Count how many elements will be extracted. */
	while (*tmp) {
	if (delim_ch == *tmp) {
	count++;
	last_comma = tmp;
	}
	tmp++;
	}

	/* Add space for trailing token. */
	count += last_comma < (str + strlen(str) - 1);

	/* Add space for terminating null string so caller
	knows where the list of returned strings ends. */
	count++;

	result = malloc(sizeof(char ) count);

	if (result) {
	size_t idx = 0;
	char *token = strtok(str, delim);

	while (token) {
	assert(idx < count);
	*(result + idx++) = strdup(token);
	token = strtok(0, delim);
	}
	assert(idx == count - 1);
	*(result + idx) = 0;
	}

	return result;
	}

	/*
	* Input directory from user, and change current working directory to
	* the user specified directory.
	*/
	void do_chdir(void)
	{
	char *line = NULL;
	size_t len = 0;
	ssize_t ret;
	int err;
	char *dirname;

	printf("dir: ");

	ret = getline(&line, &len, stdin);
	if (ret == -1) {
	fprintf(stderr, "error reading input\n");
	return;
	}

	dirname = trim(line);

	err = chdir(dirname);
	if (err == -1) {
	fprintf(stderr, "chdir failed: %s\n", strerror(errno));
	goto err_exit;
	}

	err_exit:
	free(line);
	}

	/*
	* Input command from user, and execute the command in the foreground.
	*/
	void do_exec_cmd(void)
	{
	char *line = NULL;
	size_t len = 0;
	ssize_t ret;
	pid_t cpid;
	int err;
	char **split;
	char *trimed;

	printf("cmd: ");

	ret = getline(&line, &len, stdin);
	if (ret == -1) {
	fprintf(stderr, "error reading input\n");
	return;
	}

	trimed = trim(line);
	if (strlen(trimed) == 0)
	goto err_free_line;

	split = str_split(trimed, ' ');
	if (split == NULL) {
	fprintf(stderr, "error splitting command\n");
	goto err_free_line;
	}

	cpid = fork();
	if (cpid == -1) {
	fprintf(stderr, "error creating child: %s\n", strerror(errno));
	goto err_free_split;
	}

	if (cpid == 0) {
	execvp(split[0], split);
	fprintf(stderr, "error executing cmd '%s': %s\n",
	split[0], strerror(errno));
	exit(0);
	}

	err = waitpid(cpid, NULL, 0);
	if (err == -1) {
	if (errno != ECHILD)
	fprintf(stderr, "error waiting for child: %s\n",
	strerror(errno));
	goto err_free_split;
	}

	err_free_split:
	free(split);

	err_free_line:
	free(line);
	}

	void show_help(char *menu[])
	{
	int i;

	for (i = 0; menu[i] != NULL; i++)
	printf("%s\n", menu[i]);
	}

	/*
	* Print a prompt to the user to select a menu item. If user specifies
	* an invalid option displays the menu.
	*/
	int do_prompt(char *menu[])
	{
	int i;
	char line[8];
	char *retp;

	while (1) {
	char *cwd;

	cwd = get_current_dir_name();
	if (cwd == NULL)
	cwd = "(none)";

	printf("%s$ ", cwd);
	free(cwd);

	retp = fgets(line, sizeof(line), stdin);
	if (retp == NULL)
	return EOF;

	for (i = 0; menu[i] != NULL; i++) {
	if (line[0] == menu[i][0])
	return line[0];
	}

	fprintf(stderr, "unrecognized input: %c\n", line[0]);
	show_help(menu);
	}

	return 0;
	}

	/*
	* Main application entry point.
	*/
	int main(int argc, char *argv[])
	{
	char *main_menu[] = {
	"c: Change Directory",
	"f: Execute Command",
	"x: Exit",
	"h: Help",
	NULL,
	};


	while (1) {
	int cmd = do_prompt(main_menu);

	switch (cmd) {
	case 'c':
	do_chdir();
	break;
	case 'f':
	do_exec_cmd();
	break;
	case 'h':
	show_help(main_menu);
	break;
	case 'x':
	case EOF:
	return 0;
	}
	}
	}