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doc: overhaul documentation

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This commit cleans up the README and splits portions of it out into
a user guide (GUIDE.md) and a FAQ (FAQ.md). The README now provides a
small list of documentation "quick" links to various parts of the docs.

This commit also does a few other minor touchups.
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2018-02-06 18:49:30 -05:00
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## User Guide
This guide is intended to give an elementary description of ripgrep and an
overview of its capabilities. This guide assumes that ripgrep is
[installed](README.md#installation)
and that readers have passing familiarity with using command line tools. This
also assumes a Unix-like system, although most commands are probably easily
translatable to any command line shell environment.
### Table of Contents
* [Basics](#basics)
* [Recursive search](#recursive-search)
* [Automatic filtering](#automatic-filtering)
* [Manual filtering: globs](#manual-filtering-globs)
* [Manual filtering: file types](#manual-filtering-file-types)
* [Replacements](#replacements)
* [Configuration file](#configuration-file)
* [File encoding](#file-encoding)
* [Common options](#common-options)
### Basics
ripgrep is a command line tool that searches your files for patterns that
you give it. ripgrep behaves as if reading each file line by line. If a line
matches the pattern provided to ripgrep, then that line will be printed. If a
line does not match the pattern, then the line is not printed.
The best way to see how this works is with an example. To show an example, we
need something to search. Let's try searching ripgrep's source code. First
grab a ripgrep source archive from
https://github.com/BurntSushi/ripgrep/archive/0.7.1.zip
and extract it:
```
$ curl -LO https://github.com/BurntSushi/ripgrep/archive/0.7.1.zip
$ unzip 0.7.1.zip
$ cd ripgrep-0.7.1
$ ls
benchsuite grep tests Cargo.toml LICENSE-MIT
ci ignore wincolor CHANGELOG.md README.md
complete pkg appveyor.yml compile snapcraft.yaml
doc src build.rs COPYING UNLICENSE
globset termcolor Cargo.lock HomebrewFormula
```
Let's try our first search by looking for all occurrences of the word `fast`
in `README.md`:
```
$ rg fast README.md
75: faster than both. (N.B. It is not, strictly speaking, a "drop-in" replacement
88: color and full Unicode support. Unlike GNU grep, `ripgrep` stays fast while
119:### Is it really faster than everything else?
124:Summarizing, `ripgrep` is fast because:
129: optimizations to make searching very fast.
```
So what happened here? ripgrep read the contents of `README.md`, and for each
line that contained `fast`, ripgrep printed it to your terminal. ripgrep also
included the line number for each line by default. If your terminal supports
colors, then your output might actually look something like this screenshot:
[![A screenshot of a sample search ripgrep](https://burntsushi.net/stuff/ripgrep-guide-sample.png)](https://burntsushi.net/stuff/ripgrep-guide-sample.png)
In this example, we searched for something called a "literal" string. This
means that our pattern was just some normal text that we asked ripgrep to
find. But ripgrep supports the ability to specify patterns via [regular
expressions](https://en.wikipedia.org/wiki/Regular_expression). As an example,
what if we wanted to find all lines have a word that contains `fast` followed
by some number of other letters?
```
$ rg 'fast\w+' README.md
75: faster than both. (N.B. It is not, strictly speaking, a "drop-in" replacement
119:### Is it really faster than everything else?
```
In this example, we used the pattern `fast\w+`. This pattern tells ripgrep to
look for any lines containing the letters `fast` followed by *one or more*
word-like characters. Namely, `\w` matches characters that compose words (like
`a` and `L` but unlike `.` and ` `). The `+` after the `\w` means, "match the
previous pattern one or more times." This means that the word `fast` won't
match because there are no word characters following the final `t`. But a word
like `faster` will. `faste` would also match!
Here's a different variation on this same theme:
```
$ rg 'fast\w*' README.md
75: faster than both. (N.B. It is not, strictly speaking, a "drop-in" replacement
88: color and full Unicode support. Unlike GNU grep, `ripgrep` stays fast while
119:### Is it really faster than everything else?
124:Summarizing, `ripgrep` is fast because:
129: optimizations to make searching very fast.
```
In this case, we used `fast\w*` for our pattern instead of `fast\w+`. The `*`
means that it should match *zero* or more times. In this case, ripgrep will
print the same lines as the pattern `fast`, but if your terminal supports
colors, you'll notice that `faster` will be highlighted instead of just the
`fast` prefix.
It is beyond the scope of this guide to provide a full tutorial on regular
expressions, but ripgrep's specific syntax is documented here:
https://docs.rs/regex/0.2.5/regex/#syntax
### Recursive search
In the previous section, we showed how to use ripgrep to search a single file.
In this section, we'll show how to use ripgrep to search an entire directory
of files. In fact, *recursively* searching your current working directory is
the default mode of operation for ripgrep, which means doing this is very
simple.
Using our unzipped archive of ripgrep source code, here's how to find all
function definitions whose name is `write`:
```
$ rg 'fn write\('
src/printer.rs
469: fn write(&mut self, buf: &[u8]) {
termcolor/src/lib.rs
227: fn write(&mut self, b: &[u8]) -> io::Result<usize> {
250: fn write(&mut self, b: &[u8]) -> io::Result<usize> {
428: fn write(&mut self, b: &[u8]) -> io::Result<usize> { self.wtr.write(b) }
441: fn write(&mut self, b: &[u8]) -> io::Result<usize> { self.wtr.write(b) }
454: fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
511: fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
848: fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
915: fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
949: fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
1114: fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
1348: fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
1353: fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
```
(**Note:** We escape the `(` here because `(` has special significance inside
regular expressions. You could also use `rg -F 'fn write('` to achieve the
same thing, where `-F` interprets your pattern as a literal string instead of
a regular expression.)
In this example, we didn't specify a file at all. Instead, ripgrep defaulted
to searching your current directory in the absence of a path. In general,
`rg foo` is equivalent to `rg foo ./`.
This particular search showed us results in both the `src` and `termcolor`
directories. The `src` directory is the core ripgrep code where as `termcolor`
is a dependency of ripgrep (and is used by other tools). What if we only wanted
to search core ripgrep code? Well, that's easy, just specify the directory you
want:
```
$ rg 'fn write\(' src
src/printer.rs
469: fn write(&mut self, buf: &[u8]) {
```
Here, ripgrep limited its search to the `src` directory. Another way of doing
this search would be to `cd` into the `src` directory and simply use `rg 'fn
write\('` again.
### Automatic filtering
After recursive search, ripgrep's most important feature is what it *doesn't*
search. By default, when you search a directory, ripgrep will ignore all of
the following:
1. Files and directories that match the rules in your `.gitignore` glob
pattern.
2. Hidden files and directories.
3. Binary files. (ripgrep considers any file with a `NUL` byte to be binary.)
4. Symbolic links aren't followed.
All of these things can be toggled using various flags provided by ripgrep:
1. You can disable `.gitignore` handling with the `--no-ignore` flag.
2. Hidden files and directories can be searched with the `--hidden` flag.
3. Binary files can be searched via the `--text` (`-a` for short) flag.
Be careful with this flag! Binary files may emit control characters to your
terminal, which might cause strange behavior.
4. ripgrep can follow symlinks with the `--follow` (`-L` for short) flag.
As a special convenience, ripgrep also provides a flag called `--unrestricted`
(`-u` for short). Repeated uses of this flag will cause ripgrep to disable
more and more of its filtering. That is, `-u` will disable `.gitignore`
handling, `-uu` will search hidden files and directories and `-uuu` will search
binary files. This is useful when you're using ripgrep and you aren't sure
whether its filtering is hiding results from you. Tacking on a couple `-u`
flags is a quick way to find out. (Use the `--debug` flag if you're still
perplexed, and if that doesn't help,
[file an issue](https://github.com/BurntSushi/ripgrep/issues/new).)
ripgrep's `.gitignore` handling actually goes a bit beyond just `.gitignore`
files. ripgrep will also respect repository specific rules found in
`$GIT_DIR/info/exclude`, as well as any global ignore rules in your
`core.excludesFile` (which is usually `$XDG_CONFIG_HOME/git/ignore` on
Unix-like systems).
Sometimes you want to search files that are in your `.gitignore`, so it is
possible to specify additional ignore rules or overrides in a `.ignore`
(application agnostic) or `.rgignore` (ripgrep specific) file.
For example, let's say you have a `.gitignore` file that looks like this:
```
log/
```
This generally means that any `log` directory won't be tracked by `git`.
However, perhaps it contains useful output that you'd like to include in your
searches, but you still don't want to track it in `git`. You can achieve this
by creating a `.ignore` file in the same directory as the `.gitignore` file
with the following contents:
```
!log/
```
ripgrep treats `.ignore` files with higher precedence than `.gitignore` files
(and treats `.rgignore` files with higher precdence than `.ignore` files).
This means ripgrep will see the `!log/` whitelist rule first and search that
directory.
Like `.gitignore`, a `.ignore` file can be placed in any directory. Its rules
will be processed with respect to the directory it resides in, just like
`.gitignore`.
For a more in depth description of how glob patterns in a `.gitignore` file
are interpreted, please see `man gitignore`.
### Manual filtering: globs
In the previous section, we talked about ripgrep's filtering that it does by
default. It is "automatic" because it reacts to your environment. That is, it
uses already existing `.gitignore` files to produce more relevant search
results.
In addition to automatic filtering, ripgrep also provides more manual or ad hoc
filtering. This comes in two varieties: additional glob patterns specified in
your ripgrep commands and file type filtering. This section covers glob
patterns while the next section covers file type filtering.
In our ripgrep source code (see [Basics](#basics) for instructions on how to
get a source archive to search), let's say we wanted to see which things depend
on `clap`, our argument parser.
We could do this:
```
$ rg clap
[lots of results]
```
But this shows us many things, and we're only interested in where we wrote
`clap` as a dependency. Instead, we could limit ourselves to TOML files, which
is how dependencies are communicated to Rust's build tool, Cargo:
```
$ rg clap -g '*.toml'
Cargo.toml
35:clap = "2.26"
51:clap = "2.26"
```
The `-g '*.toml'` syntax says, "make sure every file searched matches this
glob pattern." Note that we put `'*.toml'` in single quotes to prevent our
shell from expanding the `*`.
If we wanted, we could tell ripgrep to search anything *but* `*.toml` files:
```
$ rg clap -g '!*.toml'
[lots of results]
```
This will give you a lot of results again as above, but they won't include
files ending with `.toml`. Note that the use of a `!` here to mean "negation"
is a bit non-standard, but it was chosen to be consistent with how globs in
`.gitignore` files are written. (Although, the meaning is reversed. In
`.gitignore` files, a `!` prefix means whitelist, and on the command line, a
`!` means blacklist.)
Globs are interpreted in exactly the same way as `.gitignore` patterns. That
is, later globs will override earlier globs. For example, the following command
will search only `*.toml` files:
```
$ rg clap -g '!*.toml' -g '*.toml'
```
Interestingly, reversing the order of the globs in this case will match
nothing, since the presence of at least one non-blacklist glob will institute a
requirement that every file searched must match at least one glob. In this
case, the blacklist glob takes precedence over the previous glob and prevents
any file from being searched at all!
### Manual filtering: file types
Over time, you might notice that you use the same glob patterns over and over.
For example, you might find yourself doing a lot of searches where you only
want to see results for Rust files:
```
$ rg 'fn run' -g '*.rs'
```
Instead of writing out the glob every time, you can use ripgrep's support for
file types:
```
$ rg 'fn run' --type rust
```
or, more succinctly,
```
$ rg 'fn run' -trust
```
The way the `--type` flag functions is simple. It acts as a name that is
assigned to one or more globs that match the relevant files. This lets you
write a single type that might encompass a broad range of file extensions. For
example, if you wanted to search C files, you'd have to check both C source
files and C header files:
```
$ rg 'int main' -g '*.{c,h}'
```
or you could just use the C file type:
```
$ rg 'int main' -tc
```
Just as you can write blacklist globs, you can blacklist file types too:
```
$ rg clap --type-not rust
```
or, more succinctly,
```
$ rg clap -Trust
```
That is, `-t` means "include files of this type" where as `-T` means "exclude
files of this type."
To see the globs that make up a type, run `rg --type-list`:
```
$ rg --type-list | rg '^make:'
make: *.mak, *.mk, GNUmakefile, Gnumakefile, Makefile, gnumakefile, makefile
```
By default, ripgrep comes with a bunch of pre-defined types. Generally, these
types correspond to well known public formats. But you can define your own
types as well. For example, perhaps you frequently search "web" files, which
consist of Javascript, HTML and CSS:
```
$ rg --type-add 'web:*.html' --type-add 'web:*.css' --type-add 'web:*.js' -tweb title
```
or, more succinctly,
```
$ rg --type-add 'web:*.{html,css,js}' -tweb title
```
The above command defines a new type, `web`, corresponding to the glob
`*.{html,css,js}`. It then applies the new filter with `-tweb` and searches for
the pattern `title`. If you ran
```
$ rg --type-add 'web:*.{html,css,js}' --type-list
```
Then you would see your `web` type show up in the list, even though it is not
part of ripgrep's built-in types.
It is important to stress here that the `--type-add` flag only applies to the
current command. It does not add a new file type and save it somewhere in a
persistent form. If you want a type to be available in every ripgrep command,
then you should either create a shell alias:
```
alias rg="rg --type-add 'web:*.{html,css,js}'"
```
or add `--type-add=web:*.{html,css,js}` to your ripgrep configuration file.
([Configuration files](#configuration-file) are covered in more detail later.)
### Replacements
ripgrep provides a limited ability to modify its output by replacing matched
text with some other text. This is easiest to explain with an example. Remember
when we searched for the word `fast` in ripgrep's README?
```
$ rg fast README.md
75: faster than both. (N.B. It is not, strictly speaking, a "drop-in" replacement
88: color and full Unicode support. Unlike GNU grep, `ripgrep` stays fast while
119:### Is it really faster than everything else?
124:Summarizing, `ripgrep` is fast because:
129: optimizations to make searching very fast.
```
What if we wanted to *replace* all occurrences of `fast` with `FAST`? That's
easy with ripgrep's `--replace` flag:
```
$ rg fast README.md --replace FAST
75: FASTer than both. (N.B. It is not, strictly speaking, a "drop-in" replacement
88: color and full Unicode support. Unlike GNU grep, `ripgrep` stays FAST while
119:### Is it really FASTer than everything else?
124:Summarizing, `ripgrep` is FAST because:
129: optimizations to make searching very FAST.
```
or, more succinctly,
```
$ rg fast README.md -r FAST
[snip]
```
In essence, the `--replace` flag applies *only* to the matching portion of text
in the output. If you instead wanted to replace an entire line of text, then
you need to include the entire line in your match. For example:
```
$ rg '^.*fast.*$' README.md -r FAST
75:FAST
88:FAST
119:FAST
124:FAST
129:FAST
```
Alternatively, you can combine the `--only-matching` (or `-o` for short) with
the `--replace` flag to achieve the same result:
```
$ rg fast README.md --only-matching --replace FAST
75:FAST
88:FAST
119:FAST
124:FAST
129:FAST
```
or, more succinctly,
```
$ rg fast README.md -or FAST
[snip]
```
Finally, replacements can include capturing groups. For example, let's say
we wanted to find all occurrences of `fast` followed by another word and
join them together with a dash. The pattern we might use for that is
`fast\s+(\w+)`, which matches `fast`, followed by any amount of whitespace,
followed by any number of "word" characters. We put the `\w+` in a "capturing
group" (indicated by parentheses) so that we can reference it later in our
replacement string. For example:
```
$ rg 'fast\s+(\w+)' README.md -r 'fast-$1'
88: color and full Unicode support. Unlike GNU grep, `ripgrep` stays fast-while
124:Summarizing, `ripgrep` is fast-because:
```
Our replacement string here, `fast-$1`, consists of `fast-` followed by the
contents of the capturing group at index `1`. (Capturing groups actually start
at index 0, but the `0`th capturing group always corresponds to the entire
match. The capturing group at index `1` always corresponds to the first
explicit capturing group found in the regex pattern.)
Capturing groups can also be named, which is sometimes more convenient than
using the indices. For example, the following command is equivalent to the
above command:
```
$ rg 'fast\s+(?P<word>\w+)' README.md -r 'fast-$word'
88: color and full Unicode support. Unlike GNU grep, `ripgrep` stays fast-while
124:Summarizing, `ripgrep` is fast-because:
```
It is important to note that ripgrep **will never modify your files**. The
`--replace` flag only controls ripgrep's output. (And there is no flag to let
you do a replacement in a file.)
### Configuration file
It is possible that ripgrep's default options aren't suitable in every case.
For that reason, and because shell aliases aren't always convenient, ripgrep
supports configuration files.
Setting up a configuration file is simple. ripgrep will not look in any
predetermined directory for a config file automatically. Instead, you need to
set the `RIPGREP_CONFIG_PATH` environment variable to the file path of your
config file. Once the environment variable is set, open the file and just type
in the flags you want set automatically. There are only two rules for
describing the format of the config file:
1. Every line is a shell argument, after trimming ASCII whitespace.
2. Lines starting with `#` (optionally preceded by any amount of
ASCII whitespace) are ignored.
In particular, there is no escaping. Each line is given to ripgrep as a single
command line argument verbatim.
Here's an example of a configuration file, which demonstrates some of the
formatting peculiarities:
```
$ cat $HOME/.ripgreprc
# Don't let ripgrep vomit really long lines to my terminal.
--max-columns=150
# Add my 'web' type.
--type-add
web:*.{html,css,js}*
# Set the colors.
--colors=line:none
--colors=line:style:bold
# Because who cares about case!?
--smart-case
```
When we use a flag that has a value, we either put the flag and the value on
the same line but delimited by an `=` sign (e.g., `--max-columns=150`), or we
put the flag and the value on two different lines. This is because ripgrep's
argument parser knows to treat the single argument `--max-columns=150` as a
flag with a value, but if we had written `--max-columns 150` in our
configuration file, then ripgrep's argument parser wouldn't know what to do
with it.
Putting the flag and value on different lines is exactly equivalent and is a
matter of style.
Comments are encouraged so that you remember what the config is doing. Empty
lines are OK too.
So let's say you're using the above configuration file, but while you're at a
terminal, you really want to be able to see lines longer than 150 columns. What
do you do? Thankfully, all you need to do is pass `--max-columns 0` (or `-M0`
for short) on the command line, which will override your configuration file's
setting. This works because ripgrep's configuration file is *prepended* to the
explicit arguments you give it on the command line. Since flags given later
override flags given earlier, everything works as expected. This works for most
other flags as well, and each flag's documentation states which other flags
override it.
If you're confused about what configuration file ripgrep is reading arguments
from, then running ripgrep with the `--debug` flag should help clarify things.
The debug output should note what config file is being loaded and the arugments
that have been read from the configuration.
Finally, if you want to make absolutely sure that ripgrep *isn't* reading a
configuration file, then you can pass the `--no-config` flag, which will always
prevent ripgrep from reading extraneous configuration from the environment,
regardless of what other methods of configuration are added to ripgrep in the
future.
### File encoding
[Text encoding](https://en.wikipedia.org/wiki/Character_encoding) is a complex
topic, but we can try to summarize its relevancy to ripgrep:
* Files are generally just a bundle of bytes. There is no reliable way to know
their encoding.
* Either the encoding of the pattern must match the encoding of the files being
searched, or a form of transcoding must be performed converts either the
pattern or the file to the same encoding as the other.
* ripgrep tends to work best on plain text files, and among plain text files,
the most popular encodings likely consist of ASCII, latin1 or UTF-8. As
a special exception, UTF-16 is prevalent in Windows environments
In light of the above, here is how ripgrep behaves:
* All input is assumed to be ASCII compatible (which means every byte that
corresponds to an ASCII codepoint actually is an ASCII codepoint). This
includes ASCII itself, latin1 and UTF-8.
* ripgrep works best with UTF-8. For example, ripgrep's regular expression
engine supports Unicode features. Namely, character classes like `\w` will
match all word characters by Unicode's definition and `.` will match any
Unicode codepoint instead of any byte. These constructions assume UTF-8,
so they simply won't match when they come across bytes in a file that aren't
UTF-8.
* To handle the UTF-16 case, ripgrep will do something called "BOM sniffing"
by default. That is, the first three bytes of a file will be read, and if
they correspond to a UTF-16 BOM, then ripgrep will transcode the contents of
the file from UTF-16 to UTF-8, and then execute the search on the transcoded
version of the file. (This incurs a performance penalty since transcoding
is slower than regex searching.)
* To handle other cases, ripgrep provides a `-E/--encoding` flag, which permits
you to specify an encoding from the
[Encoding Standard](https://encoding.spec.whatwg.org/#concept-encoding-get).
ripgrep will assume *all* files searched are the encoding specified and
will perform a transcoding step just like in the UTF-16 case described above.
By default, ripgrep will not require its input be valid UTF-8. That is, ripgrep
can and will search arbitrary bytes. The key here is that if you're searching
content that isn't UTF-8, then the usefulness of your pattern will degrade. If
you're searching bytes that aren't ASCII compatible, then it's likely the
pattern won't find anything. With all that said, this mode of operation is
important, because it lets you find ASCII or UTF-8 *within* files that are
otherwise arbitrary bytes.
Finally, it is possible to disable ripgrep's Unicode support from within the
pattern regular expression. For example, let's say you wanted `.` to match any
byte rather than any Unicode codepoint. (You might want this while searching a
binary file, since `.` by default will not match invalid UTF-8.) You could do
this by disabling Unicode via a regular expression flag:
```
$ rg '(?-u:.)'
```
This works for any part of the pattern. For example, the following will find
any Unicode word character followed by any ASCII word character followed by
another Unicode word character:
```
$ rg '\w(?-u:\w)\w'
```
### Common options
ripgrep has a lot of flags. Too many to keep in your head at once. This section
is intended to give you a sampling of some of the most important and frequently
used options that will likely impact how you use ripgrep on a regular basis.
* `-h`: Show ripgrep's condensed help output.
* `--help`: Show ripgrep's longer form help output. (Nearly what you'd find in
ripgrep's man page, so pipe it into a pager!)
* `-i/--ignore-case`: When searching for a pattern, ignore case differences.
That is `rg -i fast` matches `fast`, `fASt`, `FAST`, etc.
* `-S/--smart-case`: This is similar to `--ignore-case`, but disables itself
if the pattern contains any uppercase letters. Usually this flag is put into
alias or a config file.
* `-w/--word-regexp`: Require that all matches of the pattern be surrounded
by word boundaries. That is, given `pattern`, the `--word-regexp` flag will
cause ripgrep to behave as if `pattern` were actually `\b(?:pattern)\b`.
* `-c/--count`: Report a count of total matched lines.
* `--files`: Print the files that ripgrep *would* search, but don't actually
search them.
* `-a/--text`: Search binary files as if they were plain text.
* `-z/--search-zip`: Search compressed files (gzip, bzip2, lzma, xz). This is
disabled by default.
* `-C/--context`: Show the lines surrounding a match.
* `--sort-files`: Force ripgrep to sort its output by file name. (This disables
parallelism, so it might be slower.)
* `-L/--follow`: Follow symbolic links while recursively searching.
* `-M/--max-columns`: Limit the length of lines printed by ripgrep.
* `--debug`: Shows ripgrep's debug output. This is useful for understanding
why a particular file might be ignored from search, or what kinds of
configuration ripgrep is loading from the environment.