Initial commit

Makefile

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+rush: rush.c color.c constants.h history.c
+	gcc -o rush rush.c color.c history.c
+all:
+	rush

README.md

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+# rush
+
+rush is a minimalistic shell for Unix systems written in C.
+
+# Dependencies
+- gcc
+
+# Building
+```sh
+$ make
+```
+
+# Usage
+```sh
+$ ./rush
+```
+
+# Features
+- Showing current time and directory with custom color
+- syntax highlighting on valid commands using ANSI colors
+- history navigation using up and down keys
+
+# Todo Features
+- Pipe
+- stdin, stdout, stderr redirect
+- background jobs
+- editing using left and right arrow keys
+- history command
+- export command to setenv
+- tab completion
+
+# Credits
+- [Tutorial - Write a shell in C](https://brennan.io/2015/01/16/write-a-shell-in-c/)
+- [dash](https://github.com/danishprakash/dash)
+- [Shell assignment](https://www.cs.cornell.edu/courses/cs414/2004su/homework/shell/shell.html)
+- [khol](https://github.com/SanketDG/khol/)

color.c

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+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+// color str in place
+
+void color_text(char str[], const char *color) {
+    int size = snprintf(NULL, 0, "\x1b[38;2;%sm%s\x1b[0m", color, str) + 1; // calculate size that is needed for colored string
+    if (size < 0) {
+        fprintf(stderr, "rush: snprintf failed\n");
+        exit(EXIT_FAILURE);
+    }
+    char *buf = malloc(size);
+    if (buf == NULL) {
+        fprintf(stderr, "rush: Memory allocation failed\n");
+        exit(EXIT_FAILURE);
+    }
+
+    snprintf(buf, size, "\x1b[38;2;%sm%s\x1b[0m", color, str); // format string to buf
+    strcpy(str, buf);
+    free(buf);
+}

color.h

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+#ifndef COLOR_H_
+#define COLOR_H_
+
+const char *lavender = "174;174;255";
+const char *pink = "255;210;239";
+const char *blue = "137;180;250";
+
+void color_text(char str[], const char *color);
+
+#endif

constants.h

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+#ifndef CONSTANTS_H_
+#define CONSTANTS_H_
+
+#define HISTFILE ".rush_history" // history file name
+#define TOK_BUFSIZE 64 // buffer size of each token
+#define RL_BUFSIZE 1024
+#define TOK_DELIM " \t\r\n\a" // delimiter for token
+
+#endif

history.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "constants.h"
+
+FILE *history_file;
+char *histfile_path;
+int cmd_count = 0;
+
+void check_history_file() {
+    char *env_home;
+    env_home = getenv("XDG_CONFIG_HOME");
+    if (env_home == NULL) {
+        // fallback to $HOME if $XDG_CONFIG_HOME is null
+        env_home = getenv("HOME");
+    }
+    int env_home_len = strlen(env_home);
+    int histfilename_len = strlen(HISTFILE);
+    int path_len = env_home_len + histfilename_len + 2; // 2 for slash and null byte
+    histfile_path = malloc(sizeof(char) * path_len);
+    // concatenate home and history file name to a path
+    strcat(histfile_path, env_home);
+    strcat(histfile_path, "/");
+    strcat(histfile_path, HISTFILE);
+    histfile_path[path_len] = '\0';
+    if (access(histfile_path, F_OK) != 0) { // check for file existence
+        history_file = fopen(histfile_path, "w"); // read and write, if doesn't exist, create
+        if (history_file == NULL) {
+            fprintf(stderr, "rush: Error opening history file\n");
+            exit(EXIT_FAILURE);
+        }
+        fclose(history_file);
+    }
+}
+
+void save_command_history(char *command) {
+    history_file = fopen(histfile_path, "a+");
+    if (history_file == NULL) {
+        fprintf(stderr, "rush: Error opening history file\n");
+        exit(EXIT_FAILURE);
+    }
+    int cmd_len = strlen(command);
+    command[cmd_len] = '\n'; // put new line feed to split commands
+    // ptr to first obj, size of each obj, number of obj, file ptr
+    fwrite(command, sizeof(char), cmd_len + 1, history_file);
+    fclose(history_file);
+}
+
+char *read_command(int direction) {
+    history_file = fopen(histfile_path, "rb"); // read binary mode
+    if (history_file == NULL) {
+        fprintf(stderr, "rush: Error opening history file\n");
+        exit(EXIT_FAILURE);
+    }
+    // normal bufsize is 1024, we serach for 1025 bytes for new line feed
+    int search_len = RL_BUFSIZE + 1;
+    char search[search_len];
+    fseek(history_file, -search_len, SEEK_END); // go back 1025 characters from end of file
+    int count = fread(search, 1, search_len - 1, history_file); // try to read 1025 characters from file, returning count number of bytes
+    search[count] = '\0';
+    char *last_nlf = strrchr(search, '\n'); // locate last occurence of \n in a searching string
+    if (last_nlf == NULL) {
+        // no history
+        return NULL;
+    }
+    if (direction == 1) { // up
+        cmd_count++;
+    } else { // down
+        if (cmd_count == 0) {
+            return NULL;
+        } else {
+            cmd_count--;
+        }
+    }
+    for (int i = 0; i < cmd_count; i++) {
+        search[last_nlf - search] = '\0'; // terminate string earlier to find second last \n, search points to first char and last_nlf is last \n, difference is the index of \n
+        last_nlf = strrchr(search, '\n'); // call strrchr 2 times to get second last new line feed in search string as every life is new line feed
+        if ((last_nlf - search) == (strchr(search, '\n') - search)) {
+            // check if the first \n is the last \n we searching for, if yes it is first command
+            cmd_count--;
+            search[last_nlf - search] = '\0'; // terminate string earlier to find second last \n, search points to first char and last_nlf is last \n, difference is the index of \n
+            char *first_cmd = malloc(sizeof(char) * (last_nlf - search) + 1);
+            strcpy(first_cmd, search);
+            return first_cmd;
+        }
+    }
+    fclose(history_file);
+    return last_nlf + 1; // return the string from the new line feed
+}

history.h

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+#ifndef HISTORY_H_
+#define HISTORY_H_
+
+void save_command_history(char *command);
+void check_history_file();
+char *read_command(int direction);
+
+#endif

rush.c

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+#include <sys/wait.h>
+#include <termios.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <limits.h>
+#include <time.h>
+#include <stdbool.h>
+#include <errno.h>
+
+#include "color.h"
+#include "constants.h"
+#include "history.h"
+
+/*
+ * Function Declarations for builtin shell commands:
+ */
+int rush_cd(char **args);
+int help(char **args);
+int rush_exit(char **args);
+
+
+/*
+ * List of builtin commands, followed by their corresponding functions.
+ */
+char *builtin_str[] = {
+    "cd",
+    "help",
+    "exit"
+};
+
+int (*builtin_func[]) (char **) = {
+    &rush_cd,
+    &help,
+    &rush_exit
+};
+
+int rush_num_builtins() {
+    return sizeof(builtin_str) / sizeof(char *);
+}
+
+// change directory
+int rush_cd(char **args) {
+    if (args[1] == NULL) {
+        char *home = getenv("HOME");
+        if (chdir(home) != 0) {
+            perror("rush");
+        }
+    } else {
+        if (chdir(args[1]) != 0) {
+            perror("rush");
+        }
+    }
+    return 1;
+}
+
+// show help menu
+int help(char **args) {
+    printf("rush v0.01-alpha\n");
+    printf("Built in commands:\n");
+
+    for (int i = 0; i < rush_num_builtins(); i++) {
+        printf("  %s\n", builtin_str[i]);
+    }
+
+    printf("Use 'man' to read manual of programs\n");
+    printf("Licensed under GPL v3\n");
+    return 1;
+}
+
+int rush_exit(char **args) {
+    return 0; // exit prompting loop, which also the shell
+}
+
+/**
+  @brief Launch a program and wait for it to terminate.
+  @param args Null terminated list of arguments (including program).
+  @return Always returns 1, to continue execution.
+  */
+int rush_launch(char **args) {
+    pid_t pid, wpid;
+    int status;
+
+    pid = fork();
+    if (pid == 0) {
+        // Child process
+        if (execvp(args[0], args) == -1) {
+            if (errno == ENOENT) {
+                fprintf(stderr, "rush: command not found: %s\n", args[0]);
+            }
+        }
+        exit(EXIT_FAILURE);
+    } else if (pid < 0) {
+        perror("Cannot fork");
+    } else {
+        // Parent process
+        do {
+            wpid = waitpid(pid, &status, WUNTRACED);
+        } while (!WIFEXITED(status) && !WIFSIGNALED(status));
+    }
+
+    return 1;
+}
+
+/**
+  @brief Execute shell built-in or launch program.
+  @param args Null terminated list of arguments.
+  @return 1 if the shell should continue running, 0 if it should terminate
+  */
+int rush_execute(char **args) {
+    if (args[0] == NULL) {
+        // An empty command was entered.
+        return 1;
+    }
+
+    for (int i = 0; i < rush_num_builtins(); i++) {
+        if (strcmp(args[0], builtin_str[i]) == 0) {
+            return (*builtin_func[i])(args);
+        }
+    }
+
+    return rush_launch(args);
+}
+
+void change_terminal_attribute(int option) {  
+    static struct termios oldt, newt;
+    tcgetattr(STDIN_FILENO, &oldt);
+    if (option) {
+        newt = oldt;
+        newt.c_lflag &= ~(ICANON | ECHO); // allows getchar without pressing enter key and echoing the character twice
+        tcsetattr(STDIN_FILENO, TCSANOW, &newt); // set settings to stdin
+    } else {
+        tcsetattr(STDIN_FILENO, TCSANOW, &oldt); // restore to old settings
+    }
+}  
+
+char **setup_path_variable() {
+    char *envpath = getenv("PATH");
+    char *path_cpy = malloc(sizeof(char) * (strlen(envpath) + 1));
+    char *path = malloc(sizeof(char) * (strlen(envpath) + 1));
+    strcpy(path_cpy, envpath);
+    strcpy(path, envpath);
+    int path_count = 0;
+    while (*path_cpy != '\0') {
+        // count number of : to count number of elements
+        if (*path_cpy == ':') {
+            path_count++;
+        }
+        path_cpy++;
+    }
+    path_count += 2; // adding one to be correct and one for terminator
+    char **paths = malloc(sizeof(char *) * path_count);
+    char *token = strtok(path, ":");
+    int counter = 0;
+    while (token != NULL) {
+        paths[counter] = token; // set element to the pointer of start of path
+        token = strtok(NULL, ":");
+        counter++;
+    }
+    paths[counter] = NULL;
+    return paths;
+}
+
+bool find_command(char **paths, char *command) {
+    if (strcmp(command, "") == 0) {
+        return false;
+    }
+    int counter = 0;
+    while (*paths != NULL) {
+        char current_path[PATH_MAX];
+        sprintf(current_path, "%s/%s", *paths, command);
+        if (access(current_path, X_OK) == 0) {
+            // command is executable
+            return true;
+        }
+        paths++;
+    }
+    return false;
+}
+
+char *rush_read_line(char **paths) {
+    int bufsize = RL_BUFSIZE;
+    int position = 0;
+    char *buffer = malloc(sizeof(char) * bufsize);
+    int c;
+
+    if (!buffer) {
+        fprintf(stderr, "rush: allocation error\n");
+        exit(EXIT_FAILURE);
+    }
+
+    buffer[0] = '\0';
+    while (1) {
+        c = getchar(); // read a character
+        int buf_len = strlen(buffer);
+        if (buf_len > 0) {
+            printf("\033[%dD", strlen(buffer));  // move cursor to the beginning
+            printf("\033[K"); // clear line to the right of cursor
+        }
+        // check each character user has input
+        // printf("%i\n", c);
+        switch (c) {
+            case EOF:
+                exit(EXIT_SUCCESS);
+            case 10: // enter/new line feed
+                buffer[buf_len] = '\0';
+                // clear all characters after the command
+                for (int start = buf_len + 1; buffer[start] != '\0'; start++) {
+                    buffer[start] = '\0';
+                }
+                printf("%s\n", buffer); // print back the command in prompt
+                save_command_history(buffer);
+                return buffer;
+            case 127: // backspace
+                if (buf_len >= 1) {
+                    buffer[buf_len - 1] = '\0'; // putting null character at last character to act as backspace
+                }
+                break;
+            case 27: // arrow keys comes at three characters, 27, 91, then 65-68
+                if (getchar() == 91) {
+                    int arrow_key = getchar();
+                    if (arrow_key == 65) { // up
+                        // read history file and fill prompt with latest command
+                        char *last_command = read_command(1);
+                        if (last_command != NULL) {
+                            strcpy(buffer, last_command);
+                            buf_len = strlen(buffer);
+                        }
+                        break;
+                    } else if (arrow_key == 66) { // down
+                        char *last_command = read_command(0);
+                        if (last_command != NULL) {
+                            strcpy(buffer, last_command);
+                            buf_len = strlen(buffer);
+                        }
+                        break;
+                    } else if (arrow_key == 67) { // right
+                        break;
+                    } else if (arrow_key == 68) { // left
+                        break;
+                    }
+                }
+            default:
+                if (c > 31 && c < 127) {
+                    buffer[buf_len] = c;
+                    buffer[buf_len + 1] = '\0'; // make sure printf don't print random characters
+                }
+        }
+        char *cmd_part = strchr(buffer, ' ');
+        bool valid;
+        if (cmd_part != NULL) {
+            char *cmd = malloc(sizeof(char) * (cmd_part - buffer + 1));
+            for (int i = 0; i < (cmd_part - buffer); i++) {
+                cmd[i] = buffer[i];
+            }
+            cmd[cmd_part - buffer] = '\0';
+            valid = find_command(paths, cmd);
+        } else {
+            valid = find_command(paths, buffer);
+        }
+        if (valid) {
+            printf("\x1b[38;2;000;255;000m%s\x1b[0m", buffer); // print green as valid command
+        } else {
+            printf("\x1b[38;2;255;000;000m%s\x1b[0m", buffer); // print red as sinvalid command
+        }
+        fflush(stdout);
+
+        // If we have exceeded the buffer, reallocate.
+        if ((buf_len + 1) >= bufsize) {
+            bufsize += RL_BUFSIZE;
+            buffer = realloc(buffer, bufsize);
+            if (!buffer) {
+                fprintf(stderr, "rush: allocation error\n");
+                exit(EXIT_FAILURE);
+            }
+        }
+    }
+}
+
+// split line into arguments
+char **rush_split_line(char *line) {
+    int bufsize = TOK_BUFSIZE, position = 0;
+    char **tokens = malloc(bufsize * sizeof(char*));
+    char *token;
+
+    if (!tokens) {
+        fprintf(stderr, "rush: Allocation error\n");
+        exit(EXIT_FAILURE);
+    }
+
+    token = strtok(line, TOK_DELIM);
+    while (token != NULL) {
+        tokens[position] = token;
+        position++;
+
+        if (position >= bufsize) {
+            bufsize += TOK_BUFSIZE;
+            tokens = realloc(tokens, bufsize * sizeof(char*));
+            if (!tokens) {
+                fprintf(stderr, "rush: Allocation error\n");
+                exit(EXIT_FAILURE);
+            }
+        }
+
+        token = strtok(NULL, TOK_DELIM);
+    }
+    tokens[position] = NULL;
+    return tokens;
+}
+
+// continously prompt for command and execute it
+void command_loop(char **paths) {
+    char *line;
+    char **args;
+    int status = 1;
+
+    while (status) {
+        time_t t = time(NULL);
+        struct tm* current_time = localtime(&t); // get current time
+        char timestr[256];
+        char cwdstr[PATH_MAX];
+        if (strftime(timestr, sizeof(timestr), "[%H:%M:%S]", current_time) == 0) { // format time string
+            return;
+        }
+        if (getcwd(cwdstr, sizeof(cwdstr)) == NULL) { // get current working directory
+            return;
+        }
+        char time[256];
+        strcpy(time, timestr);
+        color_text(time, lavender); // lavender colored time string
+        char *cwd = malloc(sizeof(char) * PATH_MAX);
+        sprintf(cwd, "[%s]", cwdstr);
+        color_text(cwd, pink); // pink colored current directory
+        char arrow[32] = "»";
+        color_text(arrow, blue);
+        printf("%s %s %s ", time, cwd, arrow);
+
+
+        line = rush_read_line(paths);
+        args = rush_split_line(line);
+        status = rush_execute(args);
+
+        free(line);
+        free(args);
+        free(cwd);
+    };
+}
+
+
+int main(int argc, char **argv) {
+    // setup
+    check_history_file();
+    char **paths = setup_path_variable();
+    change_terminal_attribute(1); // turn off echoing and disabling getchar requires pressing enter key to return
+
+    command_loop(paths);
+
+    // cleanup
+    change_terminal_attribute(0); // change back to default settings
+    return EXIT_SUCCESS;
+}