simple_shell

A simple UNIX command interpreter that provides a user interface to access and give orders to the operating system.

Table of Contents

• Description
• File Structure
• Requirements
• Installation
• Usage
• Example of Use
• Bugs
• Authors

Description

This is a command line interpreter, or shell, in the tradition of the first Unix shell written by Ken Thompson in 1971. This was made as a project for Holberton School. In this project we apply the knowledge that we have learned in C programming language. Standard functions and system calls employed in simple_shell include:

access, execve, exit, fork, free, malloc, read, signal, wait, write.

File Structure

• AUTHORS - List of contributors to this repository
• man_1_simple_shell - Manual page for the simple_shell
• shell.h - program header file
• shell.c - main function of the shell
  • main - the main function of the program
  • ret - return function
  • extstatus - return status
  • writeexe - writes to standar error
  • writes0 - writes to standar error

Requirements

simple_shell is designed to run in the Ubuntu 20.04 LTS linux environment and to be compiled using the GNU compiler collection v. gcc 4.8.4 with flags-Wall, -Werror, -Wextra, and -pedantic.

Installation

• Clone this repository: git clone "https://github.com/Timex19/simple_shell.git"
• Change directories into the repository: cd simple_shell
• Compile: gcc -Wall -Werror -Wextra -pedantic *.c -o hsh
• Run the shell in interactive mode: ./hsh
• Or run the shell in non-interactive mode: example echo "pwd" | ./hsh

Usage

The simple_shell is designed to execute commands in a similar manner to sh, however with more limited functionality. The development of this shell is ongoing. The below features will be checked as they become available (see man page for complete information on usage):

Features

• uses the PATH
• implements builtins
• handles command line arguments
• custom strtok function
• uses exit status
• shell continues upon Crtl+C (^C)
• handles comments (#)
• handles ;
• custom getline type function
• handles && and ||
• aliases
• variable replacement

Built-ins

• exit
• env
• setenv
• unsetenv
• cd
• help
• history

Examples

1. Absolute path commands

• non interactive

$ echo "/bin/pwd" | ./hsh
$ /home/timex/simple_shell

• interactive mode

$ ./hsh
./hsh$ /bin/echo hello world
helo world
./hsh$ exit
$

2. short command

• non interactive

$ echo "pwd" | ./hsh
$ /home/timex/simple_shell

• interactive mode

$ ./hsh
./hsh$ echo hello world
helo world
./hsh$ exit
$

3. built-ins

• non interactive

$ echo "exit" | ./hsh
$ echo $?
0

• interactive mode

$ ./hsh
./hsh$ exit 98
$ echo $?
98

Some error output

$ ./hsh
./hsh$ ls /non_existing_folder
ls: cannot access '/non_existing_folder': No such file or directory
./hsh$ exit
$ echo $?
2

$ echo "non_valid_command" | ./hsh
./hsh: 1: non_valid_command: not found
$ echo $?
127

Project files

File	Description
AUTHORS	File with names of the owners and authors of this project
README.md	Nutshell description of simple_shell project
chain.c	Auxiliar functions signal_exit: handler for SIGINT signals _calloc: allocate memory and fills it with zeros
built-ins.c	Built-ins functions: check_word: evalute alpha chars in string exit_built_in: stop execution of shell env_built_in: prints environment variables
core_funs.c	Heart of simple_shell check_builtin: check if first argument is a built-int not_found_error: handler for print error when command is not found simple_exec: decision flow for command execution
path_funs.c	Function to check command in path _getenv: search variable in environment vars cmd_path: concat first argument with PATH dirs
shell.h	Header file All includes All prototypes Definition of struct params
simple_shell.c	Initialize the simple_shell execution: test: Remove \n last char readed with getline Tokenize and save in argv all arguments readed Calls simple_exec main: Initialize params struct vars Set signal listenes Print prompt (interactive mode) Read arguments with getline Handle CTRL + D to stop execution
string_function.c	First string functions file _strcat: concat string (no malloc) _strlen: get length of string rev_string: reverse a string _itoa: convert int to string _strcmp: compare two strings
string_function2.c	Second string functions file _strchr: search char in string string_function3: copy string in other one str_concat: concat string (malloc) _atoi: convert string num, to int
others: The description and purpose of other functions which are not listed under project files, but exists under the repository can be found in in the commit messages of the concerned files/functions.

Full documentation

For more info about this project you can run the man page:

$ ./man_1_simple_shell