gash

gash is a small interactive Unix-like shell written in Go. It supports builtins, external commands, pipelines, redirection, tab completion, command history, and background jobs.

Install

Install the binary with Go:

go install github.com/deltron-fr/gash/cmd/gash@latest

Or run it directly from the repository:

go run ./cmd/gash

Quick start

Start the shell:

gash

Basic examples:

pwd
cd ~/projects
echo "hello"
ls -la | grep go
go test ./... > test.log
sleep 30 &
jobs

Not yet supported

gash is intentionally small. These are not implemented yet:

• A shell scripting language
• Command substitution such as $(...)
• Job control signals such as fg, bg, SIGTSTP, and SIGCONT handling

Architecture

Implementation notes live in docs/, including an overview of the lexer, parser, executor, and readline flow.

Builtins

gash currently includes these builtins:

Command	Description
cd	Change the current working directory
pwd	Print the current working directory
echo	Print text
exit	Exit the shell
type	Show whether a command is a builtin or an executable on PATH
history	Print history or read/write history files
jobs	Show background jobs tracked by the shell
complete	Register, inspect, or remove completion scripts

Shell features

External commands

Commands that are not builtins are resolved through PATH and executed as child processes.

Pipelines

Use | to connect commands:

cat go.mod | grep module

Redirection

Supported redirection operators:

Operator	Effect
> / 1>	Redirect stdout
>> / 1>>	Append stdout
2>	Redirect stderr
2>>	Append stderr

Examples:

go test ./... > out.log
go test ./... 2> err.log
go test ./... >> out.log

Background jobs

Append & to run a command in the background:

sleep 30 &
jobs

Quoting and escaping

gash supports:

• Single quotes: 'literal text'
• Double quotes: "quoted text"
• Backslash escaping outside quotes
• Escaping " and \ inside double quotes

Examples:

echo 'hello world'
echo "hello world"
echo hello\ world

Tab completion

Tab completion supports:

• Builtin commands
• Executables found on PATH
• Files and directories in the current working directory
• Custom completion scripts registered with complete -C

History

If HISTFILE is set, gash loads history from that file on startup.

The history builtin supports:

Command	Description
history	Print all in-memory history entries
history N	Print the last N entries
history -r <file>	Read entries from a file into history
history -w <file>	Write the current history to a file
history -a <file>	Append the current session history to a file

Example:

export HISTFILE="$HOME/.gash_history"
gash

Completion scripts

The complete builtin can register an executable script as a completer for a command:

complete -C ./scripts/my-completer git
complete -p git
complete -r git

The completer is executed with:

• argv: <command-name> <current-token> <previous-token>
• env: COMP_LINE and COMP_POINT

Each completion candidate should be written on its own line.

Development

Run locally:

go run ./cmd/gash

Run tests:

go test ./...