From 37a9a5cda31f3b97dc8a14da37e5a1dd6fa99e9c Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Sat, 7 May 2022 12:47:12 -0400
Subject: docs: New USAGE.md document

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+Using `bfs`
+===========
+
+`bfs` has the same command line syntax as `find`, and almost any `find` command that works with a major `find` implementation will also work with `bfs`.
+When invoked with no arguments, `bfs` will list everything under the current directory recursively, breadth-first:
+
+```console
+$ bfs
+.
+./LICENSE
+./Makefile
+./README.md
+./completions
+./docs
+./src
+./tests.sh
+./tests
+./completions/bfs.bash
+./completions/bfs.zsh
+./docs/BUILDING.md
+./docs/CHANGELOG.md
+./docs/HACKING.md
+./docs/USAGE.md
+./docs/bfs.1
+./src/bfs.h
+...
+```
+
+
+Paths
+-----
+
+Arguments that don't begin with `-` are treated as paths to search.
+If one or more paths are specified, they are used instead of the current directory:
+
+```console
+$ bfs /usr/bin /usr/lib
+/usr/bin
+/usr/lib
+/usr/bin/bfs
+...
+/usr/lib/libc.so
+...
+```
+
+
+Expressions
+-----------
+
+Arguments that start with `-` form an *expression* which `bfs` evaluates to filter the matched files, and to do things with the files that match.
+The most common expression is probably `-name`, which matches filenames against a glob pattern:
+
+```console
+$ bfs -name '*.md'
+./README.md
+./docs/BUILDING.md
+./docs/CHANGELOG.md
+./docs/HACKING.md
+./docs/USAGE.md
+```
+
+### Operators
+
+When you put multiple expressions next to each other, both of them must match:
+
+```console
+$ bfs -name '*.md' -name '*ING*'
+./docs/BUILDING.md
+./docs/HACKING.md
+```
+
+This works because the expressions are implicitly combined with *logical and*.
+You could be explicit by writing
+
+```console
+$ bfs -name '*.md' -and -name '*ING'`
+```
+
+There are other operators like `-or`:
+
+```console
+$ bfs -name '*.md' -or -name '*.sh'
+./README.md
+./tests.sh
+./tests/find-color.sh
+./tests/ls-color.sh
+./tests/remove-sibling.sh
+./tests/sort-args.sh
+./docs/CHANGELOG.md
+./docs/HACKING.md
+./docs/BUILDING.md
+./docs/USAGE.md
+```
+
+and `-not`:
+
+```console
+$ bfs -name '*.md' -and -not -name '*ING*'
+./README.md
+./docs/CHANGELOG.md
+./docs/USAGE.md
+```
+
+### Actions
+
+Every `bfs` expression returns either `true` or `false`.
+For expressions like `-name`, that's all they do.
+But some expressions, called *actions*, have other side effects.
+
+If no actions are included in the expression, `bfs` adds the `-print` action automatically, which is why the above examples actually print any output.
+The default `-print` is supressed if any actions are given explicitly.
+Available actions include printing with alternate formats (`-ls`, `-printf`, etc.), executing commands (`-exec`, `-execdir`, etc.), deleting files (`-delete`), and stopping the search (`-quit`, `-exit`).
+
+
+Extensions
+----------
+
+`bfs` implements a few extensions not found in other `find` implementations.
+
+### `-exclude`
+
+The `-exclude` operator skips an entire subtree whenever an expression matches.
+For example, `-exclude -name .git` will exclude any files or directories named `.git` from the search results.
+`-exclude` is easier to use than the standard `-prune` action; compare
+
+    bfs -name config -exclude -name .git
+
+to the equivalent
+
+    find ! \( -name .git -prune \) -name config
+
+Unlike `-prune`, `-exclude` even works in combination with `-depth`/`-delete`.
+
+---
+
+### `-hidden`/`-nohidden`
+
+`-hidden` matches "hidden" files (dotfiles).
+`bfs -hidden` is effectively shorthand for
+
+    find \( -name '.*' -not -name . -not -name .. \)
+
+`-nohidden` is equivalent to `-exclude -hidden`.
+
+---
+
+### `-unique`
+
+This option ensures that `bfs` only visits each file once, even if it's reachable through multiple hard or symbolic links.
+It's particularly useful when following symbolic links (`-L`).
+
+---
+
+### `-color`/`-nocolor`
+
+When printing to a terminal, `bfs` automatically colors paths like GNU `ls`, according to the `LS_COLORS` environment variable.
+The `-color` and `-nocolor` options override the automatic behavior, which may be handy when you want to preserve colors through a pipe:
+
+    bfs -color | less -R
+
+If the [`NO_COLOR`](https://no-color.org/) environment variable is set, colors will be disabled by default.
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