BORING SHELL

This shell was created as a part of OS Course Assignment 2 and Assignment 3. The entire commit history can be found here.

Some Notes

• Max length of string commands is 5000 characters (can be changed in headers.h)
• Memory in pinfo is shown in KB
• Not implemented "and" and "or" operation for commands
• Background commands syntax is like bash eg cmd1 & cmd2 & cmd3
• Tested on Ubuntu 18.04 and fedora 30
• /proc and <signal.h> are required
• CTRL-D / quit command are used to exit the shell safely
• CTRL-C / CTRL-Z signal are blocked by shell
• Redirection handled like bash (no multi io)
• Piping works too

Brief documentation

• shell.c
  • contains the main while loop
  • has some signal handlers
  • prints the cwd and hostname
• parser.c
  • breaks down the input and parses it as required
  • supports &, ;, spaces, <, >, >> parsing
• ls.c
  • contains implementation for ls command
• pinfo.c
  • contains implementation for pinfo command
• nightswatch.c
  • contains implementation for nightswatch command
  • also has implementation for handling raw mode which is required for nightswatch
• zombie_killer.c
  • contains implementation for for handling children processes which have become zombies
• util.c
  • contains implementation for frequently used functions like handling ~, min, max, color output etc
  • contains implementation for cd and echo too as the implementation is trivial
  • cd supports - (previous working directory)
• headers.h
  • contains most commonly used headers
• process_maker.c
  • handles creating child processes in both background and foreground to run different executables
  • Also takes care of job related things, like adding & removing jobs
• history_handler.c
  • contains implementation for the history command which stores upto 20 commands
• env_var.c
  • implements add, remove, and getting environment variables

Self implemented commands (shell builtins)

• echo
• pwd
• ls -[la]
• exit
• clear
• pinfo
• history
• nightswatch
• getenv/setenv/unsetenv
• overkill
• jobs
• kjob
• bg/fg

To Run

• make
• ./s

To Debug

• ./s2.sh

coded on mac with the help of parallels for Linux VM