c-shell

Simple C Shell (SCS) A powerful, custom command-line shell written entirely in C. This project was built from the ground up to demonstrate advanced systems programming concepts, resulting in a feature-rich and functional shell that mimics many capabilities of standard shells like bash.

Features This shell is more than just a simple command executor. It includes a wide array of advanced features that make it a practical tool for daily use.

Core Functionality Command Execution: Executes any command found in the system's PATH.

Pipelines (|): Chains multiple commands together, piping the output of one command to the input of the next.

Example: cat file.txt | grep 'error' | wc -l

I/O Redirection: Redirects standard input (<) and standard output (>).

Example: ls -l > file_list.txt

Conditional Execution (&& and ||): Executes commands based on the success or failure of the previous command.

Example: make && ./my_program

Job Control Background Processes (&): Runs any command or pipeline in the background without blocking the shell.

Full Job Management:

jobs: Lists all current background and stopped jobs.

fg %: Brings a job to the foreground.

bg %: Resumes a stopped job in the background.

Ctrl+Z: Stops the current foreground job.

Customization and Scripting Aliases: Creates shortcuts for longer commands using alias and unalias.

Example: alias ll='ls -l -h'

Shell Variables: Supports shell variables and environment variable expansion.

Example: export MY_VAR="Hello" and echo $MY_VAR

Customizable Prompt (PS1): Allows for a fully customizable prompt string.

Supports \u (user), \h (host), \w (working directory), and $.

Example: export PS1='\u@\h:\w$ '

Startup File (~/.my_shellrc): Automatically loads a configuration file on startup to set permanent aliases and variables.

Script Execution: Can run shell scripts passed as a command-line argument.

User Interface Command History: Navigates through previous commands using the Up and Down arrow keys.

Tab Completion: Provides auto-completion for executables and file paths.

Getting Started Compilation To compile the shell, you will need gcc and the standard C libraries.

gcc -o my_shell simple_shell.c

Running the Shell There are two ways to run the shell:

Interactive Mode: For day-to-day use.

./my_shell

Script Mode: To execute a script file.

./my_shell your_script.sh

Example Usage

1. Create a Startup File To customize your shell, create a file at ~/.my_shellrc:

~/.my_shellrc

My favorite aliases

alias ll='ls -l -h' alias ..='cd ..'

Set a custom prompt

export PS1='[\u@\h \w]$ '

The next time you start ./my_shell, these settings will be loaded automatically.

2. Example Session Here is a sample session demonstrating some of the shell's features:

Start the shell. The custom prompt from .my_shellrc should appear.

[user@hostname ~]$ ll

The 'll' alias is executed.

[user@hostname ~]$ mkdir project && cd project

Creates a directory and enters it only if creation was successful.

[user@hostname ~/project]$ echo "Hello, $USER. This is a test." > test.txt

Uses variable expansion and output redirection.

[user@hostname ~/project]$ sleep 20 &

Runs a job in the background.

[1] 12345

[user@hostname ~/project]$ jobs

Lists the running sleep job.

[1] 12345 Running sleep 20

[user@hostname ~/project]$ fg %1

Brings the sleep job to the foreground and waits for it to finish.

This project was created to explore the depths of C programming and operating system concepts. Enjoy using your powerful new shell!

project by MANAV HOWAL AKA ARES