https://github.com/r-lib/rex
Friendly regular expressions for R.
https://github.com/r-lib/rex
Last synced: 9 days ago
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Friendly regular expressions for R.
- Host: GitHub
- URL: https://github.com/r-lib/rex
- Owner: r-lib
- License: other
- Created: 2014-09-23T01:13:17.000Z (over 10 years ago)
- Default Branch: main
- Last Pushed: 2024-03-12T22:42:22.000Z (about 1 year ago)
- Last Synced: 2025-03-29T19:06:07.196Z (16 days ago)
- Language: R
- Homepage: https://rex.r-lib.org
- Size: 4.81 MB
- Stars: 334
- Watchers: 12
- Forks: 27
- Open Issues: 22
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- jimsghstars - r-lib/rex - Friendly regular expressions for R. (R)
README
# Rex
[](https://app.codecov.io/gh/kevinushey/rex?branch=main)
[](https://lifecycle.r-lib.org/articles/stages.html)
[](https://github.com/kevinushey/rex/actions/workflows/R-CMD-check.yaml)
### Friendly Regular Expressions
Regular expressions are very powerful feature, however they are often difficult
to interpret. Rex allows you to build complex regular expressions from human
readable expressions. So instead of writing (and later trying to decipher)
```r
r <- "^(?:(((?:[^:])+)://))?((?:(?:(?!:/).)*)+)(?:(:([[:digit:]]+)))?(?:(/.*))?$"
```
You can write
```r
r <- rex(
start,
## match the protocol -- may exist or may not
maybe(capture(
capture(except_some_of(":")),
"://"
)),
## match the path
capture(one_or_more(not(":/"))),
## get the port
maybe(capture(":", capture(numbers))),
## and the rest
maybe(capture("/", anything)),
end
)
```
While these expressions are a bit longer than their corresponding regular
expression, they are much more readable and maintainable.
## Installation
```r
install.packages("rex")
```
## Usage
The vignettes have longer form usage examples.
- [URL Validation](http://rpubs.com/jimhester/rex-url_parsing)
- [Webserver Log Parsing](http://rpubs.com/jimhester/rex-log_parsing)
Each `rex()` function call can include a number of functions and shortcuts.
For a full list of the functions available please see `?rex` and `?shortcuts`.
### Rex Mode
Rex functions are not exported because they are only useful within `rex()`
calls, but they can be temporarily attached using `rex_mode()` which allows
them to be auto-completed.
### Using Rex in other packages
Using `rex` in other packages will generate spurious NOTEs from `R CMD check`
unless you include a call to `rex::register_shortcuts()` with your package name
somewhere in your package source. This function registers all of the rex
shortcuts as valid variables fixing the NOTEs.
## See Also
- [Regularity](https://github.com/andrewberls/regularity) - Ruby library that
partially inspired `rex`.
- [PCRE](http://www.pcre.org/) - Perl Compatible Regular Expressions, the
engine that `rex` regular expressions use.
- [Perl 5 Regular Expressions](https://perldoc.perl.org/perlre) - Perl
regular expression documentation, which are nearly 100% compatible with PCRE.