ish

A purely interactive shell.

No scripting, no POSIX compat, no plugins.

Features

Prompt

josh@mac ~/d/ish* main $

• User, host, abbreviated working directory, git branch, exit status color
• PWD shortens middle components: ~/.config/fish becomes ~/.c/fish
• Green on success, red on failure
• Git branch from .git/HEAD (cached, no subprocess). Detached HEAD shows short hash
• Red * when __DENV_DIRTY=1

Line Editing

Key	Action
Ctrl+A / Home	Beginning of line
Ctrl+E / End	End of line
Ctrl+K	Kill to end of line
Ctrl+U	Kill to start of line
Ctrl+W / Ctrl+Backspace	Kill word backward
Ctrl+Y	Yank (paste) killed text
Ctrl+D	Delete forward / exit on empty line
Ctrl+C	Cancel line
Ctrl+L	Clear screen
Left / Right	Move by character
Ctrl+Left / Alt+B	Move word left
Ctrl+Right / Alt+F	Move word right

Single kill ring shared across Ctrl+K/U/W. Full UTF-8 support.

Multiline editing: paste a multi-line command (with \ continuations or unclosed quotes) and move freely with Up/Down between lines. No more unwinding — the entire command lives in one buffer with free cursor movement.

History

Key	Action
Up / Down	Prefix search through history
Ctrl+R	Fuzzy search (subsequence, case-insensitive)

Fuzzy search opens a pager with matching characters highlighted in yellow. Up/Down to navigate, Enter to accept, Escape to cancel.

Scored ranking: results are ranked by match quality, not just recency. Contiguous matches (searching "target" finds literal target/release/ first), word-boundary alignment (deb prefers debug/ over scattered d-e-b), and PWD context (entries mentioning the current project rank higher). Optimal alignment via forward+backward scan finds the tightest match window — "test" in "the best test" finds the contiguous "test" at the end, not scattered letters.

Stored at ~/.local/share/ish/history (or $XDG_DATA_HOME/ish/history). Deduplicated on add.

File Finder

Key	Action
Ctrl+F	Open file finder
Down (in query)	Toggle hidden mode
Enter	Search / accept selection
Up / Down (in results)	Navigate
Backspace (in results)	Back to query
Escape	Cancel

Type a pattern, press Enter, pick from results. The selected path is inserted at the cursor position — type vim , press Ctrl+F, pick a file, get vim src/main.rs.

Native implementation: recursive readdir with gitignore support, no external dependencies. Results sorted by depth (shallowest first) so nearby files appear before deeply nested ones. Normal mode respects .gitignore; hidden mode shows everything except .git/.

Sub-millisecond for gitignore-respecting searches (~0.85ms). No indexes, no background processes.

Tab Completion

Context	Behavior
Empty line	Inserts cd
After cd	Directories only
$ prefix	Environment variables
Everything else	Files and directories

Completions display in a column-major grid (up to 6 columns, 10 visible rows). Navigate with arrow keys or Tab, accept with Enter, cancel with Escape. Typing filters live. Path completions sorted by modification time (most recent first) so recently-built or recently-edited files appear at the top.

Colors: blue for directories, cyan for symlinks, green for executables.

Syntax

Pipes and chaining:

ls -la | grep foo > out.txt && echo done
cat err.log |& head          # pipe stderr too
make 2> err.log              # redirect stderr
make &> all.log              # redirect both
cmd1 || cmd2 ; cmd3

Quoting:

echo 'literal $HOME'         # single quotes: no expansion
echo "hello $USER"           # double quotes: variables expand
echo it\'s\ a\ test          # backslash escaping

Continuation: unclosed quotes, trailing |, &&, || prompt for more input.

Comments with #.

Expansion

~/file             # tilde → $HOME
$PATH              # environment variables
$(whoami)          # command substitution
`date`             # backtick substitution
*.rs               # glob: any characters
test?              # glob: single character
src/**/*.py        # glob: recursive descent

Expansion order: tilde, variables, command substitution, glob. Quoted characters skip expansion. No match on glob is an error.

Builtins

Command	Description
cd [dir]	Change directory. cd - for previous
exit [code]	Exit (warns if job suspended)
fg	Resume suspended job
set [VAR [val]]	Set env var. No args lists all
unset VAR...	Remove env vars
alias [name [cmd]]	Define/list aliases
l [path]	Native directory listing
c	Clear screen
w / which / type	Locate command
echo [args]	Print arguments
pwd	Print working directory
true / false	Return 0 / 1
copy-scrollback	Copy session to clipboard via OSC 52

l — Native Directory Listing

Equivalent to ls -plAhG, implemented without forking:

drwxr-xr-x  12 josh  staff   384B  Mar 17 10:23  src/
-rw-r--r--   1 josh  staff   1.2K  Mar 17 09:15  Cargo.toml
lrwxr-xr-x   1 josh  staff    11B  Mar 10 14:02  link -> target/debug
-rwxr-xr-x   1 josh  staff   184K  Mar 17 17:54  ish

Human-readable sizes. Colors: blue dirs, cyan symlinks, green executables, red setuid. Sorted case-insensitively. Resolves owner/group names via getpwuid/getgrgid.

Aliases

Define at the prompt or in config:

alias ll l
alias gs git status

Aliases expand inline when you press space. w/which/type check aliases first.

Job Control

Ctrl+Z suspends the foreground job. fg resumes it. One job slot — simple and intentional. Shell warns before exiting with a suspended job (exit again to force).

If a pipeline was suspended mid-chain (a && b, suspended during a), fg resumes and continues the chain.

denv Integration

Automatic .envrc/.env loading when denv is in PATH. Runs on every cd with a fast-path check (file mtimes vs sentinel) to skip the subprocess when nothing changed. denv allow, denv deny, denv reload work as expected.

Config

~/.config/ish/config.ish (or $XDG_CONFIG_HOME/ish/config.ish):

# Environment
set EDITOR nvim
set PAGER less

# Aliases
alias ll l
alias gs git status
alias .. "cd .."

Two directives: set and alias. Variables expand in values. Comments with #.

Non-Features (by Design)

Every omission is deliberate. No scripting engine means no code injection, no source-based exploits, no eval chains. No if/for/while/functions means no control flow to hijack. No ${VAR} brace expansion means no expansion-based attacks. One suspended job (no & backgrounding) means no resource exhaustion through job spawning. No plugins means no supply chain.

The result: the entire shell is a single flat pipeline executor with a small, auditable attack surface. If you can't source it, you can't trick a user into source-ing it.

• No scripting. ish script.sh prints an error.
• No POSIX compliance.
• No source, no eval, no ${VAR} brace expansion.
• No if/for/while/functions.
• No plugins, no prompt customization, no themes.
• No background jobs (&). One suspended job only.

Architecture

Single binary crate, one dependency (libc).

The shell never subprocesses for its own operations — directory listing, git detection, glob expansion, environment loading checks are all native. Only user commands get fork/exec'd.

Signal handling uses the self-pipe pattern. Each pipeline gets its own process group. Terminal foreground control via tcsetpgrp. Raw mode via termios.