The playground

Open the interactive terminal to run the Rust parsh interpreter and real uutils coreutils compiled to WebAssembly.

Your first command

The $ () prompt supplies the outer parentheses. Type echo hello and press Enter, or paste complete expressions and press Enter:

(echo "hello, parsh")
(let here (pwd))
(echo (str "working in " $here))
(| (sort fruits.txt) (uniq -c))
(|> results.txt (<| numbers.txt (sort -n)))
(cat results.txt)

Commands print their output directly. Expressions such as (str hello) display their return value (for example, the text "hello"). Nil and command exit statuses are not printed.

Commands and files

The following 29 commands use the real uutils implementations:

echo, printf, pwd, ls, cat, head, tail, sort, uniq, wc, seq, cut, tr, tee, nl, base64, sha256sum, basename, dirname, mkdir, rmdir, touch, cp, mv, rm, test, true, false, printenv.

The initial working directory is /home/playground, containing fruits.txt, numbers.txt, and README.txt. /tmp is also available. HOME, PWD, LANG, and TERM are initialized for this isolated session; $args is empty. export changes the environment passed to subsequent commands.

Files, cd, explicit glob, command capture, pipes, and all parsh redirection operators work within the same temporary filesystem:

(mkdir -p demo)
(cd demo)
(|> greeting.txt (echo hello))
(|>> greeting.txt (echo parsh))
(cp greeting.txt copy.txt)
(printf "%s\n" (glob *.txt))
(if (test -f copy.txt) (cat copy.txt) (echo missing))
(cd ..)

Nested commands capture UTF-8 stdout, remove trailing LF characters, and keep the result as one argument. Explicit output redirections inside the captured expression take precedence. Files and pipelines preserve binary bytes.

Browser pipelines run one stage at a time with buffered output. They report the rightmost nonzero status, but do not reproduce native streaming or SIGPIPE behavior. stdin is EOF unless supplied by a file or pipeline. Each command’s output and each pipeline buffer are limited to 8 MiB; the virtual filesystem is limited to 32 MiB. Commands such as grep, sed, and find and interactive programs are not included.

Sessions and keys

• Tab completes commands, temporary paths, and $variable names. Multiple matches extend the common prefix; press Tab again to list them. For example, cat fru followed by Tab completes fruits.txt.
• Enter evaluates the entire buffer, supplying one final ) if needed. Unfinished input continues on a new line; Ctrl+J always inserts a newline. Typing ) and pasting only edit text. A pasted batch is checked in full before execution.
• Paredit is always enabled: typed brackets and quotes pair automatically, deletion preserves their boundaries, and three consecutive quotes create a triple-quoted pair. Ctrl+Alt+F/B navigates expressions; Ctrl+Right/Left slurps/barfs forward and Ctrl+Alt+Left/Right does so backward. Alt+( wraps and Alt+S splices. Auto-inserted closers belong to the source; paste keeps text unchanged.
• Up/Down move between lines or recall history. Ctrl+P/N always browse history. Recall displays the complete source and places the cursor before the outer ), ready to append arguments or press Enter to run it again.
• Emacs-style word editing, Ctrl+Y yanking, Alt+Y cycling, Ctrl+T transposition, Ctrl+L clearing, and Ctrl+_ undo are supported. Ctrl+R/S searches history; Enter/Esc accepts without executing and Ctrl+G restores the draft. Alt keys also accept an Esc prefix. See interactive editing. Browser-reserved shortcuts may not reach the terminal.
• Unicode editing, multiline input, full-script paste, and batch validation use the shared native editor model.
• Clear and idle Ctrl+C preserve files, bindings, and the working directory.
• Reset, refresh, or leaving the page ends the temporary session; browser back-forward caching can temporarily preserve a page.
• During execution, Ctrl+C immediately stops and resets the entire session.
• An expression running for more than 5 seconds automatically resets the session, including files, variables, functions, environment, and history.
• exit and Ctrl+D on empty input end the session; reset to restart.

To work with your own files and Linux programs, run parsh on Linux.

Synchronous command references, apply, capture-call, raw-byte results, $?, and try/catch/throw/finally share native semantics. The browser has no native signal or background-task support; spawn, wait, job-status, and cancel report that capability limit.