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Build your own Shell

Learn about parsing shell commands, executing programs and more

Start Building
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This challenge is free until 1 April 2025!

A shell is a command-line interface that executes commands and manages processes. In this challenge, you'll build your own POSIX compliant shell that's capable of interpreting shell commands, running external programs and builtin commands like cd, pwd, echo and more.

Along the way, you'll learn about shell command parsing, REPLs, builtin commands, and more.

Stages

Print a prompt
Handle invalid commands
REPL
The exit builtin
The echo builtin
The type builtin: builtins
The type builtin: executable files
Run a program

Redirection

Redirect stdout
Redirect stderr
Append stdout
Append stderr

Quoting

Single quotes
Double quotes
Backslash outside quotes
Backslash within single quotes
Backslash within double quotes
Executing a quoted executable

Navigation

The pwd builtin
The cd builtin: Absolute paths
The cd builtin: Relative paths
The cd builtin: Home directory

Autocompletion

Builtin completion
Completion with arguments
Missing completions
Executable completion
Multiple completions
Partial completions
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