grex generates regular expressions from user-provided test cases

grex is a library as well as a command-line utility that is meant to simplify the often complicated and tedious task of creating regular expressions. It does so by automatically generating a single regular expression from user-provided test cases. The resulting expression is guaranteed to match the test cases which it was generated from.

The philosophy of this project is to generate the most specific regular expression possible by default which exactly matches the given input only and nothing else. With the use of command-line flags (in the CLI tool) or preprocessing methods (in the library), more generalized expressions can be created.

The produced expressions are Perl-compatible regular expressions which are also compatible with the regular expression parser in Rust’s regex crate. Other regular expression parsers or respective libraries from other programming languages have not been tested so far, but they ought to be mostly compatible as well.

This is free and open source software.

Features include:

• Literals.
• Character classes.
• Detection of common prefixes and suffixes.
• Detection of repeated substrings and conversion to {min,max} quantifier notation.
• Alternation using | operator.
• Optionality using ? quantifier.
• Escaping of non-ascii characters, with optional conversion of astral code points to surrogate pairs.
• Case-sensitive or case-insensitive matching.
• Capturing or non-capturing groups.
• Optional anchors ^ and $.
• Fully compliant to Unicode Standard 15.0.
• Fully compatible with regex crate 1.9.0+.
• Correctly handles graphemes consisting of multiple Unicode symbols.
• Reads input strings from the command-line or from a file.
• Produces more readable expressions indented on multiple using optional verbose mode.
• Optional syntax highlighting for nicer output in supported terminals.

Digit Options:
-d, --digits Converts any Unicode decimal digit to \d
-D, --non-digits Converts any character which is not a Unicode decimal digit to \D

Whitespace Options:
-s, --spaces Converts any Unicode whitespace character to \s
-S, --non-spaces Converts any character which is not a Unicode whitespace character to \S

Word Options:
-w, --words Converts any Unicode word character to \w
-W, --non-words Converts any character which is not a Unicode word character to \W

Escaping Options:
-e, --escape Replaces all non-ASCII characters with unicode escape sequences
--with-surrogates Converts astral code points to surrogate pairs if –escape is set

Repetition Options:
-r, --repetitions
Detects repeated non-overlapping substrings and converts them to {min,max} quantifier
notation
--min-repetitions
Specifies the minimum quantity of substring repetitions to be converted if –repetitions
is set [default: 1]
--min-substring-length
Specifies the minimum length a repeated substring must have in order to be converted if
--repetitions is set [default: 1]

Anchor Options:
--no-start-anchor Removes the caret anchor `^` from the resulting regular expression
--no-end-anchor Removes the dollar sign anchor `$` from the resulting regular expression
--no-anchors Removes the caret and dollar sign anchors from the resulting regular
expression

Display Options:
-x, --verbose Produces a nicer-looking regular expression in verbose mode
-c, --colorize Provides syntax highlighting for the resulting regular expression

Miscellaneous Options:
-i, --ignore-case Performs case-insensitive matching, letters match both upper and lower case
-g, --capture-groups Replaces non-capturing groups with capturing ones
-h, --help Prints help information
-v, --version Prints version information

Website: github.com/pemistahl/grex
Support:
Developer: Peter M. Stahl
License: Apache License 2.0

grex is written in Rust. Learn Rust with our recommended free books and free tutorials.

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