https://github.com/estnafinema0/rainbowshell
A custom Unix shell written in C, featuring pipes, redirections, subshells, logical operators, and background jobs with a colorful startup message.
https://github.com/estnafinema0/rainbowshell
background-jobs c-language command-parsing linux-terminal shell-redirections subshells systems-programming unix-shell
Last synced: 9 months ago
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A custom Unix shell written in C, featuring pipes, redirections, subshells, logical operators, and background jobs with a colorful startup message.
- Host: GitHub
- URL: https://github.com/estnafinema0/rainbowshell
- Owner: estnafinema0
- Created: 2024-11-29T20:44:37.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2025-02-03T19:33:29.000Z (11 months ago)
- Last Synced: 2025-02-15T15:48:59.480Z (11 months ago)
- Topics: background-jobs, c-language, command-parsing, linux-terminal, shell-redirections, subshells, systems-programming, unix-shell
- Language: C
- Homepage:
- Size: 62.5 KB
- Stars: 2
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# RainbowShell - Custom Unix Shell
Welcome to **RainbowShell**, my educational but powerful custom Unix shell written in C. RainbowShell implements **pipes**, **redirections**, **logical operators**, **subshells**, and **background jobs** while also featuring a **rainbow/gradient** greeting message (builtes `color.h` library).
> **Note**: This is a project for the 3rd semester at CMC MSU (summarizing skills of systems programming, process handling, shell scripting concepts).
---
## Table of Contents
- [RainbowShell - Custom Unix Shell](#rainbowshell---custom-unix-shell)
- [Table of Contents](#table-of-contents)
- [Features](#features)
- [Build](#build)
- [Usage](#usage)
- [Project Structure](#project-structure)
- [Examples](#examples)
- [Background Jobs](#background-jobs)
---
## Features
- **Rainbow Greeting**
When you launch RainbowShell, you’re greeted with a colorful gradient welcome message. Because, who don't want to meet a rainbow 🌈 ?
- **Custom Command Parser**
- Supports multi-stage pipelines: `cmd1 | cmd2 | cmd3`
- Understands logical operators: `&&`, `||`
- Sequential execution: `cmd1 ; cmd2`
- Subshells: `(cd / && ls -l)`
- Redirections: `< file`, `> file`, `>> file`
- Background tasks: `cmd &`
- **Built-in Commands**
- `cd `: change directory (built-in, because changing directories in a child process has no effect on the parent)
- **Error Handling**
- Lexer and parser produce meaningful, color-highlighted error messages (typos, missing quotes, etc).
- Handles partial command failures in pipelines (ex. if the last command in a pipeline fails, subsequent `&&` sections won’t run).
- **Background Jobs**
- Run commands asynchronously with `&`.
- Automatically ignores `SIGINT` (Ctrl-C) in the background job so it won’t be interrupted.
- Prevents zombie processes via `waitpid`.
- **Subshell & Grouping**
- Parentheses `( ... )` create a new job in a subshell.
Example: `(cd /; ls); pwd`
- You can group multiple commands, run them in the background, or combine with logical operators.
- **Extensible Architecture**
- Separation of **lexer**, **parser**, and **executor**.
- Because of it future features or built-ins can be easily added.
---
## Build
1. **Clone** this repository:
```bash
git clone https://github.com/estnafinema0/RainbowShell.git
cd RainbowShell/shell
```
2. **Compile** using `make`:
```bash
make
```
Now we have executable `Rainbowshell`.
3. **Run** RainbowShell:
```bash
./Rainbowshell
```
---
## Usage
Now you are open to type any commands as in a standard Unix shell.
```bash
shell> echo "Hello World"
```
Use **Ctrl-C** to send an interrupt signal to **foreground** commands. If a command is run in the background (using `&`), it won’t be interrupted by **Ctrl-C** (as it should be in a usual shell!).
---
## Project Structure
- **main.c**
Entry point for RainbowShell. Handles signals (`SIGINT` and `SIGCHLD`), prints the rainbow greeting, and starts the main interactive loop.
- **parser.c / parser.h**
Contains the logic for parsing command lines into a structured form (`Job` and `Command` objects). Handles operators like `&&`, `||`, `|`, `;`, `&`, as well as subshell grouping `( ... )`.
- **lexer.c / lexer.h**
Breaks the command line into tokens (`TOKEN_WORD`, `TOKEN_OPERATOR`, etc.). Also handles quoted strings and error checking for unclosed quotes.
- **executor.c / executor.h**
Executes commands by forking processes. Implements:
- Pipelines (`|`)
- Sequential commands (`;`)
- Conditional commands (`&&`, `||`)
- Subshells
- Redirections (`<`, `>`, `>>`)
- Background jobs (`&`)
- **builtins.c / builtins.h**
Built-in commands such as `cd`.
- **colors.c / colors.h**
Provides color/gradient print utilities. The `print_rainbow_text` function produces the signature rainbow greeting.
- **structures.h**
Defines the primary data structures (`Command`, `Job`, `OperatorType`) used across the shell.
- **makefile**
Contains build rules. Simply run `make`.
---
## Examples
Here are some commands to showcase RainbowShell’s broad functionality:
1. **Subshell & Sequential**
```bash
(cd /; pwd); pwd
```
- Changes directory to `/`, prints it, then returns to the parent shell and prints its current directory.
2. **Conditional Execution**
```bash
(false && echo "Skipped 1") || (echo "Fallback 1" && echo "Part of fallback")
```
- `false` fails, so `&&` chain is skipped; `||` triggers the fallback commands.
3. **Background Task with Redirection**
```bash
echo "Background task" > output.txt & cat output.txt
```
- The `echo` runs in the background, while the shell immediately proceeds to `cat output.txt`.
4. **Pipeline**
```bash
echo "hello" | grep "hello" && echo "Pipeline succeeded" || echo "Pipeline failed"
```
- If `grep "hello"` finds the text, the `&&` chain continues.
5. **Multiple Steps with Conditionals**
```bash
ls non_existent_dir && echo "This should not print" || echo "Directory not found"
```
- Fails on the nonexistent directory, triggers the `||` fallback.
6. **Process Listing and Subshell**
```bash
ps; ls; (cd .. ; ls; ps) && ls && ps
```
- Shows how a subshell can change directory without affecting the parent shell.
7. **Background Sleep**
```bash
sleep 5 & echo "Background process test"
```
- `sleep` runs in the background, while RainbowShell continues to the next command.
---
## Background Jobs
If you type `&` in the end of the command, it will launch in the background:
- **Non-blocking background**: The shell is immediately ready for the next command.
- **No Zombie Processes**: RainbowShell calls `waitpid` appropriately.
- **Ignored SIGINT**: Background jobs ignor `Ctrl-C` from the main terminal.
---
Thank you for checking out **RainbowShell**! Enjoy the rainbow!🌈