Custom Shell in C

This project is a custom shell implementation in C that supports standard shell commands, sequential and parallel execution, I/O redirection, and pipelines. It also handles signals (Ctrl+C, Ctrl+Z) gracefully and provides a basic interactive prompt.

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✨ Features

• Basic command execution

  • Runs external commands like ls, pwd, echo, etc.

  • Built-in support for:

    • cd (change directory)
    • exit (terminate the shell)

• Sequential execution (##)

  • Commands separated by ## run one after another.

  ls ## pwd ## date

• Parallel execution (&&)

  • Commands separated by && run in parallel.

  ls && date && echo "Done"

• Output redirection (>)

  • Redirects standard output of a command to a file.

  ls > out.txt

• Pipelines (|)

  • Connects multiple commands with pipes.

  ls -l | grep ".c" | wc -l

• Signal handling

  • Ctrl+C (SIGINT) and Ctrl+Z (SIGTSTP) don’t kill the shell — they just refresh the prompt.

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📂 Project Structure

.
├── myshell.c       # Main source code
└── README.md     # Documentation

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⚙️ Compilation

Use gcc to compile:

gcc myshell.c -o myshell

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🚀 Usage

Run the shell:

./myshell

You’ll see a prompt showing the current directory:

/home/user$

Examples:

/home/user$ ls
/home/user$ cd Documents
/home/user/Documents$ ls && date
/home/user/Documents$ ls ## pwd
/home/user/Documents$ ls -l | grep ".txt"

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🧩 Implementation Details

• Parsing

  • Custom parseInput() function to tokenize input by delimiters (&&, ##, >, |).

• Execution

  • Uses fork(), execvp(), and waitpid() for process handling.

• Parallel Execution

  • Forks multiple processes and waits for all.

• Sequential Execution

  • Executes commands one after another.

• Redirection

  • Uses open(), dup2() to redirect standard output.

• Pipelines

  • Sets up multiple pipes and forks processes in a chain.

• Signal Handling

  • Catches SIGINT and SIGTSTP to refresh the prompt instead of terminating the shell.

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