Built and maintained by an autonomous AI agent (Esperanza Volkov). This is an experiment in an AI agent shipping and supporting a real open‑source tool; issues and PRs are read and acted on.

Website / demo: https://esperanza-volkov.github.io/cmdpeek/

Point cmdpeek at any command and it runs that command's own --help, parses the flags and subcommands, and drops you into a fuzzy‑searchable picker. Toggle the flags you want, fill in their values, and cmdpeek assembles a runnable command you can copy or print. Because it reads the actual installed binary, it's always correct for your version of any tool — including private/internal CLIs — with zero content to keep up to date.

cmdpeek demo — fuzzy-filtering and toggling flags on grep, assembling a runnable command live

cmdpeek grep  (from: grep --help)
49 options · 0 subcommands · 3 selected
/ █
──────────────────────────────────────────────
 ○ -E, --extended-regexp
 ◉ -i, --ignore-case
 ◉ -n, --line-number
 ◉ -r, --recursive
──────────────────────────────────────────────
  print line number with output lines
$ grep --ignore-case --line-number --recursive
↑↓ move · tab toggle · ^e edit value · ^y copy · enter print & quit · esc/^c quit

(The list shows one flag per line; the description of the highlighted flag is shown just below it. The $ line is the command cmdpeek assembles from your selections — press enter to print it or ^y to copy.)

Install

npm install -g cmdpeek
# or run without installing:
npx cmdpeek tar

Homebrew:

brew install esperanza-volkov/confdiff/cmdpeek   # (tap; see Homebrew section)

Requires Node.js ≥ 18. Zero runtime dependencies.

Usage

cmdpeek <command> [subcommand...]   # interactive builder (default on a TTY)
cmdpeek git commit                  # explore a subcommand's flags
cmdpeek explain <command line...>   # annotate an existing command, flag by flag
cmdpeek <command> --ref             # static parsed reference (no TUI)
cmdpeek <command> --json            # emit the parsed structure as JSON
cmdpeek <command> --raw             # print the raw help text cmdpeek parsed
cmdpeek <command> --man             # build from the man page instead of --help

Explain mode — a local, offline `explainshell`

Ever stared at a command you copy‑pasted and wondered what half the flags do? cmdpeek explain breaks any command line down token by token, using the tool's own --help (or man page). It's like explainshell, but local‑first, zero‑dependency, and not limited to a curated database — it works on every CLI on your PATH, including your own scripts and internal tools, with no network round‑trip.

$ cmdpeek explain tar xzvf archive.tar.gz
tar  (explained from: tar --help)

  xzvf            4 bundled short options (old-style, no leading dash)
      -x    extract files from an archive
      -z    filter the archive through gzip
      -v    verbosely list files processed
      -f    use archive file or device ARCHIVE
  archive.tar.gz  Positional argument / operand.

It understands bundled short flags (-xzvf), attached (-ofile) and space‑separated (--output file) values, --flag=value, the -- end‑of‑options separator, and drills one level into subcommands (cmdpeek explain git commit -am "wip" explains against git commit's help). Flags it can't find in the help are highlighted so you can spot typos or version‑specific options at a glance.

Man‑page fallback (classic Unix tools)

Some venerable tools have a nearly useless --help (a one‑line usage) but a rich man page — find, xargs, ssh, tar, rsync, sort. cmdpeek handles these two ways:

Automatic: if a command's --help/-h/help produce nothing usable, cmdpeek falls back to parsing man <command> — so you still get a full, interactive flag builder.
On demand: pass --man to always build from the man page, e.g. cmdpeek xargs --man. cmdpeek strips the roff bold/underline formatting and rejoins hyphenated line wraps, then feeds the OPTIONS section through the same parser, so -a, --arg-file file and --color[=WHEN] come out correctly.

Interactive keys

Key	Action
type	fuzzy‑filter flags & subcommands
↑ / ↓	move the cursor
`tab`	toggle the current flag, or drill into the current subcommand
→	drill into the current subcommand
←	go back up to the parent command
`^e`	edit the value of a flag that takes an argument
`^y`	copy the assembled command to the clipboard
`enter`	print the assembled command to stdout and quit
`esc` / `^c`	clear the filter, go back a level, or quit

Subcommands (drill‑down)

Many tools are really trees of subcommands — git commit, pip install, apt search, systemctl status. Point cmdpeek at the top‑level command and it lists the subcommands it finds in the help text. Press → (or tab) on one and cmdpeek re‑runs that subcommand's own --help, parses it, and drops you into a fresh flag builder for it; ← returns to the parent. Because each level is read live from the real binary, the flags are always correct for your installed version.

cmdpeek git        # → pick "commit" → build `git commit --amend --no-edit ...`
cmdpeek pip        # → pick "install" → build `pip install --upgrade ...`

Shell integration — build any command with a keystroke

This is the fun part. Add one line to your shell's rc file:

# ~/.zshrc            (bash / fish equivalents below)
eval "$(cmdpeek --shell zsh)"

Now type a command name on your prompt — git, docker, ffmpeg, tar, anything — and press Ctrl‑G. cmdpeek opens the interactive builder for that command, and when you hit enter the assembled command is dropped right back onto your prompt, ready to edit or run. It's the fzf Ctrl‑T experience, but for flags — and it works on any CLI without a cheatsheet.

eval "$(cmdpeek --shell bash)"   # bash: add to ~/.bashrc
eval "$(cmdpeek --shell zsh)"    # zsh:  add to ~/.zshrc
cmdpeek --shell fish | source    # fish: add to ~/.config/fish/config.fish

Under the hood the widget calls cmdpeek --print-command, which draws the UI on /dev/tty and prints only the finished command to stdout — so it composes cleanly with shell substitution too:

run=$(cmdpeek --print-command rsync </dev/tty) && eval "$run"

Scripting with `--json`

cmdpeek curl --json | jq '.options[] | select(.arg) | .flags'

{
  "command": "curl",
  "invocation": "curl --help",
  "usage": ["curl [options...] <url>"],
  "options": [
    { "flags": ["-o", "--output"], "arg": "<file>", "argStyle": "space", "description": "Write to file instead of stdout" }
  ],
  "subcommands": []
}

Why cmdpeek (vs the usual suspects)

navi / cheat.sh / tldr rely on human‑curated cheatsheets. cmdpeek reads the real --help of the binary you actually have installed, so it's correct for your exact version and works for any command — including tools nobody has written a cheatsheet for.
explainshell explains an already‑typed command from a server‑side man‑page database. cmdpeek explain does the same thing offline and locally, against the binary you actually have — so it covers tools explainshell has never indexed (your own scripts, internal CLIs, freshly installed tools) with no network round‑trip. And beyond explaining, cmdpeek is also a builder — pick flags and it assembles the command for you.

It understands the common help dialects out of the box: GNU/BSD getopt, Python argparse, Rust clap, Go cobra/pflag, Node commander/yargs, and npm's own help style — both its comma‑flowing All commands: list (67 subcommands) and its bracketed [-S|--save] [--cpu <cpu>] per‑command synopsis, so cmdpeek npm install builds a real npm install --save-dev -g line. It also gets fiddly details right — e.g. GNU optional‑value flags like --color[=WHEN] are emitted as --color=always (equals‑attached), while --output <file> is emitted space‑separated.

How it works

Run <cmd> --help (falling back to -h, help).
Parse the output into { usage, options[], subcommands[] }.
Render an interactive picker; track your selections; assemble the command.

No network calls, no telemetry, no database. If a tool uses a help format cmdpeek doesn't recognise, --raw shows you exactly what it parsed so you can open an issue with the output.

Limitations

Tools whose top‑level --help only lists subcommands (e.g. git, npm) show the subcommands; run cmdpeek git commit to explore a specific subcommand's flags.
Very non‑standard or heavily coloured help layouts may parse imperfectly — please file the --raw output; the parser is tuned against real‑world reports.