hella_shell

Table of Contents

• Description
• Purpose
• Requirements
• File Structure
• Usage
• Examples
• Bugs
• Authors
• License

Description

hella_shell is a simple command line interpreter based on the first Unix shell 'sh', created by Ken Thompson in 1971. hella_shell is intentionally minimalistic and contains functionality for only the most basic shell tasks - accepting input, parsing the input into a command and its arguments, and executing that input. Error checking is simple and follows Bash conventions.

Purpose

The purpose of the simple shell project is to understand:

• how a shell works
• PID and PPIDs
• how processes are created
• the three prototypes of main
• how the shell uses the PATH to find and execute programs
• the EOF/"end-of-file" condition

Requirements

• Must follow Betty style and document guidelines
• Allowed editors: vi, vim, emacs
• Must have a README.md file
• All header files must be include guarded
• No more than 5 functions per files

File Structure

• AUTHORS - list of contributors
• check_helpers.c - helper functions that check for builtins
  • exit_check - checks if user_input is exit
  • blank_check - checks if user_input is \n
  • env_check - checks if user_input is env
• env_helpers.c - helper functions related to PATH and other environment variables
  • get_path_count - gets count of path parts
  • get_path_array - tokenizes path to 2d array
  • find_path - finds and checks path for given command
  • print_env - shell builtin that prints current environment
• error_helpers.c - helper functions that print appropriate error messages
  • command_error - command not found error
  • exec_error - command could not execute error
  • access_error - user does not have permission to execute command
  • exit_error - user has entered an invalid exit code
• fork_wait_exec.c - process and execution function
• memory_helpers.c - helper functions related to memory management
  • free_array - 2D array freeing function
• man_1_simple_shell - manual page
• number_helpers.c - helper functions pertaining to integers
  • _atoi - turns a numerical string into an integer
  • print_number - prints an integer to standard output
• parse_input.c - command and argument parsing function
• shell.c - main function
• shell.h - header file
• string_helpers.c - helper functions pertaining to string handling
  • _strlen - finds length of a string
  • _strcmp - compares two strings
  • _strdup - duplicates two strings (including memory management)
  • _putchar - writes a single character to standard output

Compilation

gcc -Wall -Wextra -Werror -pedantic *.c -o hsh

GCC 4.8.4 or later only

Usage Examples

Interactive Mode

~/me$ ./hsh
hella_shell$ echo & the bunnymen
& the bunnymen
hella_shell$ pwd
/home/me/hella_shell
hella_shell$
hella_shell$ exit
~/me$

Non-Interactive Mode

~/me$ cat hella_shell.txt | ./hsh
got me feelin' hella shell so let's just keep on codin'
~/me$

Bugs

At this time, there are no known bugs.

Authors

Lizzie Turner | GitHub | Twitter Omar Contreras | GitHub | Twitter

License

hella_shell is open source and free to download and use