Initial code commit

.gitignore

@@ -0,0 +1,2 @@
+*.out
+bin/

Makefile

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+LIBRARIES = -lreadline
+RELEASE_ARGS = -DRELEASEBUILD
+SOURCES = ./msh.c
+OUTPUT_DIR = ./bin
+OUTPUT_BIN = ${OUTPUT_DIR}/PROG
+OUTPUT = -o ${OUTPUT_BIN}
+
+build: output_dir
+	gcc -Wall -std=gnu99 ${RELEASE_ARGS} ${SOURCES} ${OUTPUT:PROG=mash} ${LIBRARIES}
+
+debug: output_dir
+	gcc -Wall -std=gnu99 -g ${SOURCES} ${OUTPUT:PROG=mash} ${LIBRARIES}
+
+output_dir:
+	mkdir -p ${OUTPUT_DIR}
+
+install:
+	mv ${OUTPUT_BIN:PROG=mash} /usr/sbin/mash

README.md

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+**IMPORTANT** this shell is **NOT** meant to be used for any serious applications.
+This is for academic purposes only!
+
+## Install
+
+```
+make
+make install
+```
+

msh.c

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+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <string.h>
+
+#include <readline/readline.h>
+#include <readline/history.h>
+
+#include "msh.h"
+
+#define clear() printf("\033[H\033[J")
+#define MATHLEN 100000
+
+static char *prompt = NULL;
+static bool skipMath = false;
+
+union pipe {
+	int fileDesc[2];
+	struct {
+		int read;
+		int write;
+	};
+};
+
+static char *builtinFunctions[] = {
+	"exit",
+	"author",
+	"cd",
+	"nomorenumbers"
+};
+
+int (*builtinFunc[]) (char **) = {
+	&builtinExit,
+	&builtinAuthor,
+	&builtinCD,
+	&builtinNMN
+};
+
+int builtinExit(char **args) {
+#if RL_READLINE_VERSION < 0x0602
+	rl_clear_history();
+#else
+	clear_history();
+#endif
+	free(args);
+	exit(EXIT_SUCCESS);
+}
+
+int builtinAuthor(char **args) {
+	static const char* message =
+		"Author: Spencer\n"
+		"Description: A shell to promote math!\n"
+		"Ask for the source code!\n"
+		"\n";
+	printf("%s", message);
+	free(args);
+	return 0;
+}
+
+int builtinCD(char **dir) {
+	int status = 0;
+	char *oldPWD = getenv("PWD");
+	char *changeDir = malloc(sizeof(char *));
+	if (dir[1] != NULL) {
+		char c = *dir[1];
+		switch (c) {
+			case '~':
+				changeDir = realloc(changeDir, strlen(getenv("HOME") + strlen(dir[1])));
+				strcpy(changeDir, getenv("HOME"));
+				strcat(changeDir, dir[1]+1);
+				break;
+			case '-':
+				changeDir = realloc(changeDir, strlen(getenv("OLDPWD")));
+				strcpy(changeDir, getenv("OLDPWD"));
+				break;
+			default:
+				changeDir = dir[1];
+				break;
+		}
+		if (chdir(changeDir) != 0) {
+			status = 1;
+			printf("bash: cd: error\n");
+		} else {
+			setenv("PWD", dir[1], 1);
+			setenv("OLDPWD", oldPWD, 1);
+			free(prompt);
+			prompt = NULL;
+		}
+	} else {
+		if (chdir(getenv("HOME")) != 0) {
+			status = 1;
+			printf("Bash: cd: error\n");
+		} else {
+			setenv("PWD", getenv("HOME"), 1);
+			setenv("OLDPWD", oldPWD, 1);
+			free(prompt);
+			prompt = NULL;
+		}
+	}
+	free(changeDir);
+	changeDir = NULL;
+	free(dir);
+	return status;
+}
+
+int builtinNMN(char **args) {
+	skipMath = true;
+	free(args);
+	return 0;
+}
+
+void failedTest() {
+	static const char* message =
+		"\n"
+		"How can you expect to execute commands without knowing any math???\n"
+		"\n";
+	printf("%s", message);
+	return;
+}
+
+int runCommand(char *command) {
+	int status = 0;
+	pid_t pid;
+
+	pid = fork();
+	if (pid == 0) { // Child process
+		if(execlp("bash", "bash", "-c", command, NULL) == -1) {
+			exit(EXIT_FAILURE);
+		}
+		exit(EXIT_SUCCESS);
+	} else if (pid < 0) {
+		printf("Error forking...\n");
+		status = 1;
+	} else { // Parent process
+		do {
+			waitpid(pid, &status, WUNTRACED);
+		} while(!WIFEXITED(status) && !WIFSIGNALED(status));
+	}
+
+	return status;
+}
+
+char **splitCMD(const char *line) {
+        size_t size = 8;
+        size_t pos = 0;
+        char **args = malloc(size * sizeof(char*));
+        char *arg = NULL;
+
+	char *lineTest = NULL;
+	lineTest = strdup(line);
+
+        if(line == NULL) {
+                *args=NULL;
+                return args;
+        }
+
+        arg = strtok(lineTest, " \t\r\n\a");
+        while (arg != NULL) {
+                args[pos] = arg;
+                pos++;
+
+                if (pos >= size) {
+                        size += 1;
+                        args = realloc(args, size * sizeof(char*));
+
+                }
+                arg = strtok(NULL, " \t\r\n\a");
+        }
+
+        args[pos] = NULL;
+        return args;
+}
+
+int execCommand(char *command) {
+	char **commandARGS = splitCMD(command);
+	for (size_t i = 0; i < (sizeof(builtinFunctions) / sizeof(char *)); i++) {
+		if (strcmp(commandARGS[0], builtinFunctions[i]) == 0) {
+			return (*builtinFunc[i])(commandARGS);
+		}
+	}
+	free(commandARGS);
+	return runCommand(command);
+}
+
+void initShell() {
+	FILE *fd;
+
+	clear();
+	using_history();
+
+	// Setting random time seed
+	srand(time(0));
+
+	fflush(stdout);
+	runCommand("uname -a");
+
+	fd = fopen("/etc/motd", "r");
+	if (fd != NULL) {
+		char c;
+		c = fgetc(fd);
+		printf("\n");
+		while (c != EOF) {
+			printf("%c", c);
+			c = fgetc(fd);
+		}
+		fclose(fd);
+	}
+
+	printf("\n");
+
+	return;
+}
+
+char *getPrompt() {
+	pid_t pid;
+	union pipe input, output;
+	FILE *outputFileD;
+	size_t len = 0;
+	int status = 0;
+
+	static size_t promptCap = 0;
+
+	pipe(input.fileDesc);
+	pipe(output.fileDesc);
+
+	pid = fork();
+	if (pid == 0) { // Child process
+		close(input.write);
+		close(output.read);
+
+		dup2(input.read, STDIN_FILENO);
+		dup2(output.write, STDOUT_FILENO);
+		close(STDERR_FILENO); // Do not print errors to the screen
+
+		execlp("bash", "bash", "-i", "-c", "\
+			ver=$(bash --version | head -n 1 | awk \'{print $4}\' | grep -o \".\\..\");\
+			check_ver=$(echo -e \"${ver}\n4.3\" | sort -V | head -n 1);\
+			if [[ \"${ver}\" == \"${check_ver}\" ]]; then\
+			  echo \"[${USER}@${HOSTNAME} ${PWD##*/}]$ \";\
+			else\
+			  echo \"${PS1@P}\";\
+			fi\
+			", NULL);
+	} else if (pid < 0) { // Error forking
+		printf("Error forking\n");
+	} else { // Parent process
+		close(input.read);
+		close(output.write);
+
+		outputFileD = fdopen(output.read, "r");
+
+		len = getline(&prompt, &promptCap, outputFileD);
+
+		if (prompt[len - 1] == '\n') {
+			prompt[len - 1] = '\0';
+		}
+
+		fclose(outputFileD);
+		do {
+			waitpid(pid, &status, WUNTRACED);
+		} while(!WIFEXITED(status) && !WIFSIGNALED(status));
+	}
+
+	return prompt;
+}
+
+int randomNum(int limit) {
+	int num = 0;
+	if (limit != 0) {
+		num = rand()%limit +1;
+	} else {
+		num = rand();
+	}
+	return num;
+}
+
+int mathTest() {
+	int status = 0;
+	long numAnswer = 0;
+	int num1 = randomNum(MATHLEN);
+	int num2 = randomNum(MATHLEN);
+	long numSolution = 0;
+	char *numLine = NULL;
+
+	const char mathOperation[] = {'+', '-', '*', '/'};
+
+	int randProblem = randomNum(3);
+
+	if (skipMath) {
+		return 0;
+	}
+
+	for(int i = 0; i < 1; i++) {
+		switch (mathOperation[randProblem]) {
+			case '+':
+				numSolution = num1 + num2;
+				break;
+			case '-':
+				numSolution = num1 - num2;
+				break;
+			case '*':
+				numSolution = num1 * num2;
+				break;
+			case '/':
+				numSolution = num1 / num2;
+				break;
+
+		}
+		#ifndef RELEASEBUILD
+		printf("Answer: %ld\n", numSolution);
+		#endif
+		printf("%d %c %d = ", num1, mathOperation[randProblem], num2);
+		numLine = readline("");
+		sscanf(numLine, "%ld", &numAnswer);
+
+		if (numSolution != numAnswer) { // If wrong answer
+			status = 1;
+		}
+	}
+
+	#ifdef RELEASEBUILD
+	printf("Calculating");
+	for (int i = 0; i < 5; i++){
+		printf(".");
+		fflush(stdout);
+		sleep(2);
+	}
+	printf("\n");
+	#endif
+
+	free(numLine);
+	return status;
+}
+
+
+void startShell() {
+	char *line = NULL;
+	int status = 0;
+
+	while ((line = readline(getPrompt())) != NULL) {
+		if (strlen(line) != 0) { // Checking if prompt returns empty
+			status = mathTest();
+			if (status == 0) { // Passed math test
+				add_history(line);
+				execCommand(line);
+			} else { // Failed math test
+				failedTest();
+			}
+		}
+		free(line);
+	}
+	free(prompt);
+	prompt = NULL;
+}
+
+void handleBreak(){
+	signal(SIGINT, handleBreak);
+	printf("\n");
+	rl_on_new_line();
+	rl_replace_line("", 0);
+	rl_redisplay();
+}
+
+int main() {
+	initShell();
+	signal(SIGINT, handleBreak);
+	startShell();
+#if RL_READLINE_VERSION < 0x0602
+	rl_clear_history();
+#else
+	clear_history();
+#endif
+	exit(EXIT_SUCCESS);
+}

msh.h

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+int builtinExit(char **args);
+int builtinAuthor(char **args);
+int builtinCD(char **dir);
+int builtinNMN(char **args);