initial commit

1 files changed, 355 insertions, 0 deletions

diff --git a/src/lush.c b/src/lush.c
new file mode 100644
index 0000000..652a0be
--- /dev/null
+++ b/src/lush.c
@@ -0,0 +1,355 @@
+/*
+Copyright (c) 2024, Lance Borden
+All rights reserved.
+
+This software is licensed under the BSD 3-Clause License.
+You may obtain a copy of the license at:
+https://opensource.org/licenses/BSD-3-Clause
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted under the conditions stated in the BSD 3-Clause
+License.
+
+THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTIES,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+*/
+
+#include "lush.h"
+#include <bits/time.h>
+#include <linux/limits.h>
+#include <pwd.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <time.h>
+#include <unistd.h>
+
+// -- builtin functions --
+char *builtin_strs[] = {"cd", "help", "exit", "time"};
+
+int (*builtin_func[])(char ***) = {&lush_cd, &lush_help, &lush_exit,
+								   &lush_time};
+
+int lush_num_builtins() { return sizeof(builtin_strs) / sizeof(char *); }
+
+int lush_cd(char ***args) {
+	uid_t uid = getuid();
+	struct passwd *pw = getpwuid(uid);
+	if (!pw) {
+		perror("retrieve home dir");
+		return 0;
+	}
+	if (args[0][1] == NULL) {
+		if (chdir(pw->pw_dir) != 0) {
+			perror("lush: cd");
+		}
+	} else {
+		char path[PATH_MAX];
+		char extended_path[PATH_MAX];
+		char *tilda = strchr(args[0][1], '~');
+		if (tilda) {
+			strcpy(path, pw->pw_dir);
+			strcat(path, tilda + 1);
+		} else {
+			strcpy(path, args[0][1]);
+		}
+		char *exp_path = realpath(path, extended_path);
+		if (!exp_path) {
+			perror("realpath");
+			return 0;
+		}
+		if (chdir(exp_path) != 0) {
+			perror("lush: cd");
+		}
+	}
+
+	return 1;
+}
+
+int lush_help(char ***args) {
+	// TODO: make this more fun
+	printf("Lunar Shell Help Page\n\n");
+	printf("Available commands: \n");
+	for (int i = 0; i < lush_num_builtins(); i++) {
+		printf("- %s\n", builtin_strs[i]);
+	}
+	return 1;
+}
+
+int lush_exit(char ***args) { return 0; }
+
+int lush_time(char ***args) {
+	// advance past time command
+	args[0]++;
+
+	// count commands
+	int i = 0;
+	while (args[i++]) {
+		;
+	}
+
+	// get time
+	struct timespec start, end;
+	double elapsed_time;
+
+	clock_gettime(CLOCK_MONOTONIC, &start);
+	int rc = lush_run(args, i);
+	clock_gettime(CLOCK_MONOTONIC, &end);
+
+	elapsed_time = (end.tv_sec - start.tv_sec) * 1000.0 +
+				   (end.tv_nsec - start.tv_nsec) / 1e6;
+	printf("Time: %.3f milliseconds", elapsed_time);
+
+	// return pointer back to "time" for free()
+	args[0]--;
+	return rc;
+}
+
+// -- shell utility --
+char *lush_read_line() {
+	char *line = NULL;
+	size_t bufsize = 0;
+	if (getline(&line, &bufsize, stdin) == -1) {
+		if (feof(stdin)) {
+			exit(EXIT_SUCCESS);
+		} else {
+			perror("readline");
+			exit(EXIT_FAILURE);
+		}
+	}
+	return line;
+}
+
+char **lush_split_pipes(char *line) {
+	char **commands = calloc(16, sizeof(char *));
+	if (!commands) {
+		perror("calloc failed");
+		exit(1);
+	}
+
+	char *command;
+	int pos = 0;
+
+	command = strtok(line, "|");
+	while (command) {
+		commands[pos++] = command;
+		command = strtok(NULL, "|");
+	}
+
+	// trim off whitespace
+	for (int i = 0; i < pos; i++) {
+		while (*commands[i] == ' ' || *commands[i] == '\n') {
+			commands[i]++;
+		}
+		char *end_of_str = strrchr(commands[i], '\0');
+		--end_of_str;
+		while (*end_of_str == ' ' || *end_of_str == '\n') {
+			*end_of_str = '\0';
+			--end_of_str;
+		}
+	}
+	return commands;
+}
+
+char ***lush_split_args(char **commands, int *status) {
+	int outer_pos = 0;
+	char ***command_args = calloc(128, sizeof(char **));
+	if (!command_args) {
+		perror("calloc failed");
+		exit(1);
+	}
+
+	for (int i = 0; commands[i]; i++) {
+		int pos = 0;
+		char **args = calloc(128, sizeof(char *));
+		if (!args) {
+			perror("calloc failed");
+			exit(1);
+		}
+
+		bool inside_string = false;
+		char *current_token = &commands[i][0];
+		for (int j = 0; commands[i][j]; j++) {
+			if (commands[i][j] == '"' && !inside_string) {
+				// beginning of a string
+				commands[i][j++] = '\0';
+				if (commands[i][j] != '"') {
+					inside_string = true;
+					current_token = &commands[i][j];
+				} else {
+					commands[i][j] = '\0';
+					current_token = &commands[i][++j];
+				}
+			} else if (inside_string) {
+				if (commands[i][j] == '"') {
+					// ending of a string
+					inside_string = false;
+					commands[i][j] = '\0';
+					args[pos++] = current_token;
+					current_token = NULL;
+				} else {
+					// character in string
+					continue;
+				}
+			} else if (commands[i][j] == ' ') {
+				// space delimeter
+				if (current_token && *current_token != ' ') {
+					args[pos++] = current_token;
+				}
+				current_token = &commands[i][j + 1]; // go past the space
+				commands[i][j] = '\0';				 // null the space
+			} else if (commands[i][j] == '$' && commands[i][j + 1] &&
+					   commands[i][j + 1] != ' ') {
+				// environment variable
+				args[pos++] = getenv(&commands[i][++j]);
+				while (commands[i][j]) {
+					++j;
+				}
+				current_token = &commands[i][j + 1];
+			} else {
+				// regular character
+				continue;
+			}
+		}
+
+		// verify that string literals are finished
+		if (inside_string) {
+			*status = -1;
+			return command_args;
+		} else if (current_token && *current_token != ' ') {
+			// tack on last arg
+			args[pos++] = current_token;
+		}
+
+		// add this commands args array to the outer array
+		command_args[outer_pos++] = args;
+	}
+
+	*status = outer_pos;
+	return command_args;
+}
+
+int lush_execute_pipeline(char ***commands, int num_commands) {
+	// no command given
+	if (commands[0][0][0] == '\0') {
+		return 1;
+	}
+
+	// create pipes for each command
+	int **pipes = malloc((num_commands - 1) * sizeof(int *));
+	for (int i = 0; i < num_commands - 1; i++) {
+		pipes[i] =
+			malloc(2 * sizeof(int)); // pipes[i][0] = in, pipes[i][1] = out
+		if (pipe(pipes[i]) == -1) {
+			perror("pipe");
+			return 0;
+		}
+	}
+
+	// execute commands in the pipeline
+	for (int i = 0; i < num_commands - 1; i++) {
+		int input_fd = (i == 0) ? STDIN_FILENO : pipes[i - 1][0];
+		int output_fd = pipes[i][1];
+
+		lush_execute_command(commands[i], input_fd, output_fd);
+		close(output_fd); // no longer need to write to this pipe
+	}
+
+	// execute last or only command
+	int input_fd =
+		(num_commands > 1) ? pipes[num_commands - 2][0] : STDIN_FILENO;
+	int output_fd = STDOUT_FILENO;
+	lush_execute_command(commands[num_commands - 1], input_fd, output_fd);
+
+	// close pipes
+	for (int i = 0; i < num_commands - 1; i++) {
+		close(pipes[i][0]);
+		close(pipes[i][1]);
+		free(pipes[i]);
+	}
+	free(pipes);
+	return 1;
+}
+
+void lush_execute_command(char **args, int input_fd, int output_fd) {
+	// create child
+	pid_t pid;
+	pid_t wpid;
+	int status;
+
+	if ((pid = fork()) == 0) {
+		// child process content
+
+		// redirect in and out fd's if needed
+		if (input_fd != STDIN_FILENO) {
+			dup2(input_fd, STDIN_FILENO);
+			close(input_fd);
+		}
+
+		if (output_fd != STDOUT_FILENO) {
+			dup2(output_fd, STDOUT_FILENO);
+			close(output_fd);
+		}
+
+		// execute the command
+		if (execvp(args[0], args) == -1) {
+			perror("execvp");
+			exit(EXIT_FAILURE);
+		}
+	} else if (pid < 0) {
+		// forking failed
+		perror("fork");
+		exit(EXIT_FAILURE);
+	} else {
+		// parent process
+		do {
+			wpid = waitpid(pid, &status, WUNTRACED);
+		} while (!WIFEXITED(status) && !WIFSIGNALED(status));
+	}
+}
+
+int lush_run(char ***commands, int num_commands) {
+	if (commands[0][0] == NULL) {
+		// no command given
+		return 1;
+	}
+
+	// check shell builtins
+	for (int i = 0; i < lush_num_builtins(); i++) {
+		if (strcmp(commands[0][0], builtin_strs[i]) == 0) {
+			return ((*builtin_func[i])(commands));
+		}
+	}
+
+	return lush_execute_pipeline(commands, num_commands);
+}
+
+int main() {
+	int status = 0;
+	while (true) {
+		// Prompt
+		char *cwd = getcwd(NULL, 0);
+		printf("%s _> ", cwd);
+
+		char *line = lush_read_line();
+		char **commands = lush_split_pipes(line);
+		char ***args = lush_split_args(commands, &status);
+		if (status == -1) {
+			fprintf(stderr, "lush: Expected end of quoted string\n");
+		} else if (lush_run(args, status) == 0) {
+			exit(1);
+		}
+
+		for (int i = 0; args[i]; i++) {
+			free(args[i]);
+		}
+		free(args);
+		free(commands);
+		free(line);
+		free(cwd);
+	}
+}