Shell-Rebuild / Minishell

Minishell is a simplified Unix shell implemented in C. It replicates key features of bash, including command parsing, pipelines, redirections, environment variable handling, and built-in commands.
The project showcases system programming skills, including low-level process control, signal handling, file descriptor management, and interaction with the Unix operating system.

Contributors

Ilia Munaev LinkedIn, Pavel Vershinin LinkedIn

Features

• Execution of simple and compound commands
• Custom Built-in commands: echo, cd, pwd, export, unset, env, exit
• Input/output redirections: <, >, >>, << (heredoc)
• Support for pipelines (|)
• Environment variable expansion ($VAR)
• Quoting rules:
  • Double quotes allow variable expansion
  • Single quotes preserve literal value
• Signal handling: Ctrl+C, Ctrl+D, Ctrl+\
• Command history using GNU Readline

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Implementation Highlights

• Written in C, with no external dependencies beyond standard custom librarie (libft) and readline
• Modular structure following a microservice-inspired architecture
• Custom tokenizer and parser
• Uses fork(), execve(), pipe(), and dup2() for process and I/O management
• Manages memory manually, verified with Valgrind for leak-free execution
• Suppression file for readline and external commands memory leaks included

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Minishell Structure (t_mshell)

The Minishell structure is the core of the Minishell. It keeps track of everything the shell needs while it's running.

It stores:

A copy of the environment variables (so the shell can access and modify them).

A hash table version of the environment for faster lookups.

The last command’s exit status (so $? works like in Bash).

The last syntax error status (useful for error handling).

A flag to detect if a memory allocation failed (to handle errors safely).

Command Strunture (t_cmd)

In Minishell, every command you type is stored in a structured format using the t_cmd struct. This includes simple commands like ls or more complex ones like ls -l | grep minishell.

t_cmd is a single command in a pipeline, like one part of ls -l | grep foo | wc -l.

It contains:

• argv: The command and its arguments, as a string array. For example: ["ls", "-l", NULL].

• binary: The actual path to the executable (like /bin/ls), resolved before running.

• next: A pointer to the next command in a pipeline (if you're using |).

• minishell: A link back to the shell's main state (t_mshell), so each command can access environment variables, error handling, etc.

• redirs: A list of redirection rules (<, >, >>, <<) attached to the command.

• origin_head: A pointer to the start of the command chain—useful for keeping track of where the pipeline began.

Redirection (t_redir)

Each redirection in a command (like < input.txt or >> output.log) is stored in a t_redir struct. It includes:

• Type of redirection (<, >, >>, <<)

• File name or heredoc delimiter

• Which file descriptor is being redirected (like stdin or stdout)

• Runtime FD used when executing

• Whether variable expansion should happen in heredoc mode

Start minishell

make && ./minishell

Clean

make fclean

Error tests

all erros + supp

valgrind --leak-check=full --trace-children=yes --gen-suppressions=all --show-leak-kinds=all --track-fds=yes  --error-limit=no --suppressions=mshell.supp ./minishell

all errors

valgrind --leak-check=full  --track-origins=yes  --trace-children=yes --gen-suppressions=all --show-leak-kinds=all --track-fds=yes --error-limit=no  ./minishell