nsh

A Minimalist Linux Terminal Shell.

Instructions to start the terminal

• Clone the repo and change directory: git clone https://github.com/NJnisarg/nsh && cd nsh/
• Run the make script: make
• While running the make command, it will ask for password, since it installs the nsh in /bin/nsh. If you don't want that please, remove it from the Makefile.
• To run the terminal: nsh
• The Makefile has 4 different targets: all, build, install and clean. build and install are ran internally by all.
• To clean up everything, run make clean. This command will also ask for sudo password since it attempts to remove the /bin/nsh entry.

Code organization

• The Terminal shell, has 2 major components: 1.) The Parser and 2.) The Executor
• The Parser component is built using Lex and Yacc and GNU Readline library, where as the executor is organized in the command.h and command.c files
• The Lex is used for getting a Tokenizer/scanner(lexical analyzer) and Yacc is used to get the Parser that parses the Grammar for the shell commands.
• The executor code and the data structures to hold the commands (Command table) are defined in the command.h and command.c files.

Features supported (Shell commands and Grammar):

• The shell tries to mimic the bash shell grammar.
• It has simple commands implemented
• It has I/O Redirections implemented
• It has Pipes and Pipelines implemented
• It supports cd
• Supports tab-completion for filenames and history and up-arrow-key command history

Features to implement

• It does not support compound commands, lists/pipeline lists and shell scripting
• It does not support shell environment and variables.