Minishell

"As beautiful as a shell"

created by - Anttoni and Mark

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🧩 What Problem Does This Minishell Solve?

This minishell reimplements core shell behavior - parsing, tokenization, process forking, I/O redirection, and signal handling - using only low-level C functions. It addresses the challenge of managing child processes, handling edge cases like unclosed quotes or Ctrl+D, and executing built-in commands without relying on standard shell utilities.

Overview

Minishell is a simple, lightweight Unix shell built from scratch. It replicates the basic functionality of Bash, offering:

• Command execution
• Environment variable management
• Piping
• Input/output redirection
• Heredoc support
• Graceful signal handling
• Robust error handling

Installation

Clone the repository:

git clone git clone git@github.com:manttoni/minishell.git
cd minishell
make

Run the shell:

./minishell

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Features

• Tokenizer: Input is tokenized gracefully, breaking it down into manageable pieces for seamless parsing and execution, even for complex commands
• Commands: Minishell can execute any command that is located in the directories specified in your $PATH
• Pipes: Combine commands using |
• Env varibles: Expands $VARNAME to a string that is stored in env. you can add and remove them with export, unset
• Redirections: Input (<), Output (>), Append (>>), Heredoc (<<)
• Exit Codes ($?):
  • Returns accurate exit codes for commands/executables, maintaining Bash-like behavior.
  • Captures the correct exit status in pipelines ($? reflects the last command in the pipeline).
  • Detects signals and handles exit codes accordingly.
• Signals: replicates the functionality of Bash
  • ctrl-C
  • ctrl-D
  • ctrl-\

Execution Flow Diagrahm

flowchart TD
    A[Start: main] --> B[init_main]
    B --> C{init_main success?}
    C -- No --> Z[Exit: free_main, clear_history]
    C -- Yes --> D[Main Loop]
    D --> E[handle_input]
    E --> F{SIGQUIT/EOF?}
    F -- Yes --> Z
    F -- No --> G[unclosed_quotes?]
    G -- Yes --> D
    G -- No --> H[tokenize_string]
    H --> I[create_list]
    I --> J{cmd_list == NULL?}
    J -- Yes --> D
    J -- No --> K[run or ft_exit]
    K --> L{ft_exit?}
    L -- Yes --> Z
    L -- No --> M[run]
    M --> N[init_run]
    N --> O{init_run success?}
    O -- No --> P[finish_run]
    P --> D
    O -- Yes --> Q[Loop: For each command]
    Q --> R{Is Builtin?}
    R -- Yes --> S[run_builtin]
    S --> Q
    R -- No --> T[do_fork]
    T --> U{fork success?}
    U -- No --> P
    U -- Yes --> V[run_child]
    V --> Q
    Q --> P
    P --> D

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Testing and Debugging

Minishell comes with built-in tools for testing and debugging to ensure reliability and detect memory issues.

Memory Leak Testing with Valgrind

The valrun.sh script allows you to run Minishell with Valgrind to detect memory leaks and other issues.

Usage

./valrun.sh

• Suppressions file: supp.supp ensures that false positives or irrelevant warnings are filtered out for cleaner output.

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Automated Testing with Tester

The /tester/ directory includes tester.sh, a script that runs over 150 test cases to verify Minishell's functionality.

Usage

cd tester
./tester.sh

Built-in Commands

Minishell implements the following built-in commands, mimicking their behavior in Bash:

Command	Description	Example
echo	Prints text to the terminal. Supports the -n option to omit the trailing newline.	echo -n "Hello, World!"
cd	Changes the current directory. Accepts relative or absolute paths.	cd /home/user
pwd	Prints the current working directory. No options are supported.	pwd
export	Sets environment variables. No options are supported.	export VAR=value
unset	Removes environment variables. No options are supported.	unset VAR
env	Displays all environment variables. No arguments or options are supported.	env
exit	Exits the shell with an optional status code.	exit 0

Usage

Example:

echo "Hello, World!" | grep "World" > output.txt

Environment Variables

export VAR=value
echo $VAR

Heredoc Example

cat << EOF
This is a heredoc example.
EOF

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