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A simple shell

Description

A recreation of a shell that takes user input (commands with arguments) and outputs accordingly.

Basic loop of a shell:

  1. Read command from standard input.
  2. Parse commandline string into an executable program and its arguments.
  3. Run parsed command.

Environment

Our custom shell was developed and tested on Ubuntu 14.04 LTS via Vagrant in VirtualBox.

Features

  • displays a prompt and waits for user to type a command
  • can handle commands with options and arguments
  • prompt displays again each time command is executed
  • uses PATH variable to find executable command
  • if executable is not found, prints an error message and displays prompt again
  • includes an exit function that exits the shell
  • includes an env built-in that prints the current environment

File Contents

This repository contains the following files:

File Description
shell.c the main function
shed.h header file
_itoa.c custom itoa function
_strcmp.c custom strcmp function
_strdup.c custom strdup function
_strlen.c custom strlen function
custom_atoi.c custom atoi function
forking_helper.c contains function to execute command read from commandline
free_array.c contains function to free array and its tokens
life.c contains a mix of important function calls
print_env.c contains function to print environment
run_shell.c contains function checking if user inputed anything
smart_cat.c contains function concatenating the command to its path directory
tokenizer.c contains function that parses the commandline string
var_finder.c contains function to find PATH variable in environment list

Function Descriptions

Function Description
int _strlen(char *s) find string length
int _strcmp(char *s1, char *s2) compare two strings
char **tokenizer(char *str, const char *delim) tokenizes commandline string
int forking_helper(char **av) executes shell
char *stupid_cat(char *path, char *name) append command name to its directory path to make actual command executable
char *_getenv(const char *name) get value of environment variable
char **splitEnv(char *str, const char *delim) tokenizes environment variable name and its value using
char *smart_cat(char **path, char *name) appends path to command to command
int print_env(char **env) print environment list
int custom_atoi(int *status, char *s) convert character to integer
char *_strdup(char *str) duplicate string
char *_itoa(int num) convert integer to characters
char *var_finder(char *var, char **env) find PATH variable
void free_array(char **array) free tokens in array and array itself
int life(char **array, char **argv, char **env, char **p_t, int i, int *e_c) calling a medley of essential functions
int run_shell(int go) check if command was entered by user

Usage

  1. Enter custom shell by typing "./hsh". You should be prompted with a ($).
  2. Type a command of your liking and press "Enter".
  3. Appropriate output will appear.
  4. Prompt reappears and awaits your next command.
  5. Exit shell by typing "exit"

Installation

Clone the repository. Compile the ".c" files. Run executable.

$ git clone https://github.com/aDENTinTIME/simple_shell.git

Compilation

Enter the following command to compile: $ gcc -Wall -Werror -Wextra -pedantic *.c -o hsh

Example

Interactive Mode

$ ./hsh
($) /bin/ls
hsh main.c shell.c
($)
($) exit
$

Non-interactive Mode

$ echo "/bin/ls" | ./hsh
hsh main.c shell.c test_ls_2
$
$ cat test_ls_2
/bin/ls
/bin/ls
$
$ cat test_ls_2 | ./hsh
hsh main.c shell.c test_ls_2
hsh main.c shell.c test_ls_2
$

Authors

Acknowledgements

We would like to thank the staff and our wonderful peers at Holberton School for providing an effective learning experience throughout this project.