minishell

A bash-like shell written in C: parsing, expansion, pipes, redirections, and builtins.

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Table of contents

• Core capabilities
• Architecture
• Build & run
• Builtins
• Usage examples
• Project structure
• Limitations

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Core capabilities

• Interactive prompt with readline-backed line editing and history
• Executable resolution via PATH, plus absolute/relative paths
• Single and double quote parsing, including nested and adjacent quoting
• Variable expansion ($VAR, $?) inside double quotes and bare words
• Pipelines (|) with correct file-descriptor wiring across arbitrarily many stages
• Full redirection suite: <, >, >>, << (heredoc)
• bash-compatible signal handling for Ctrl+C, Ctrl+D, Ctrl+\
• Builtins implemented in-process (no fork for cd, export, etc., matching real shell semantics)

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Architecture

main.c → readline prompt → tokenizer → parser → expansion → execution
                                                                ├── builtins   (in-process)
                                                                └── pipeline   (fork/exec/pipe/wait)

Module	Responsibility
parsing/	Tokenization, quote handling, AST/command-list construction, syntax validation
execution/	Process management: fork/exec, pipe wiring, redirections, exit-status propagation
builtins/	echo, cd, pwd, export, unset, env, exit
utils/	String, memory, and environment-array helpers shared across modules
libft/	Custom C utility library, linked into every module

Commands are processed in four stages: tokenize → parse (build command structures, validate syntax) → expand (resolve $VAR/$?) → execute (fork children, wire pipes/redirections, wait).

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Build & run

Requirements: gcc/cc, make, an internet connection for the first build (downloads readline 8.2)

make        # downloads + builds readline 8.2, builds libft, compiles minishell
./minishell

make clean  # remove object files
make fclean # remove object files, binary, and the vendored readline build
make re     # fclean + build

The first build takes longer since it compiles readline from source; subsequent builds are fast.

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Builtins

Command	Syntax	Description
echo	echo [-n] [text...]	Print text, -n suppresses the trailing newline
cd	cd [path]	Change directory (relative/absolute)
pwd	pwd	Print the working directory
export	export [VAR=value]	Set or display environment variables
unset	unset [VAR]	Remove an environment variable
env	env	List environment variables
exit	exit [status]	Exit with an optional status code

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Usage examples

minishell> echo "Goodbye, World?"
Goodbye, World?

minishell> ls -la | grep minishell > output.txt
minishell> cat << EOF | sort | uniq >> results.txt
heredoc line 1
heredoc line 2
EOF

minishell> export MY_VAR="test value"
minishell> echo "Value: $MY_VAR, Exit code: $?"
Value: test value, Exit code: 0

minishell> export USER="Melovi"
minishell> echo "'Hello $USER'" vs '"Hello $USER"'
'Hello Melovi' vs "Hello $USER"

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Project structure

.
├── srcs/
│   ├── builtins/    # echo, cd, pwd, export, unset, env, exit
│   ├── execution/   # Process management and execution
│   ├── parsing/     # Tokenization and command parsing
│   ├── utils/        # Helper functions
│   └── main.c
├── includes/        # Headers and prototypes
├── libft/           # Custom C utility library
└── supps/           # Valgrind/readline suppression files

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Limitations

• No arrow-key history navigation (only readline's in-session line editing)
• Backslash escaping is not implemented
• No command substitution (`cmd`/$(cmd)) or wildcard/glob expansion