How to use the command 'exrex' (with examples)

The ’exrex’ command is a tool that generates all possible or random matching strings for a given regular expression. It can also simplify regular expressions. This tool is useful for various purposes, including testing regular expressions, generating test data, or exploring different string patterns.

Use case 1: Generate all possible strings that match a regular expression

Code:

exrex 'regular_expression'

Motivation: One might want to generate all possible strings that match a specific regular expression for testing or validation purposes.

Explanation: This command takes a regular expression as an argument and generates all possible strings that match the given expression.

Example output: For the regular expression ab*c, the command exrex 'ab*c' will generate the following strings:

ac
abc
abbc
abbbc
...

Use case 2: Generate a random string that matches a regular expression

Code:

exrex --random 'regular_expression'

Motivation: Generating a random string that satisfies a regular expression can be useful for creating random data for testing or simulation purposes.

Explanation: The --random flag generates a single random string that matches the given regular expression.

Example output: For the regular expression [0-9]{3}-[0-9]{3}-[0-9]{4}, the command exrex --random '[0-9]{3}-[0-9]{3}-[0-9]{4}' might generate a random phone number such as 987-654-3210.

Use case 3: Generate a specific number of strings that match a regular expression

Code:

exrex --max-number 100 'regular_expression'

Motivation: Generating a limited number of strings that match a regular expression can be useful when working with large or complex regular expressions and only a subset of matches is required.

Explanation: The --max-number flag specifies the maximum number of strings to generate that match the given regular expression.

Example output: For the regular expression [A-Za-z]{10}, the command exrex --max-number 5 '[A-Za-z]{10}' will generate five random strings with ten alphabetic characters each, such as GlPmuDAgED.

Use case 4: Generate all possible strings that match a regular expression, joined by a custom delimiter string

Code:

exrex --delimiter ", " 'regular_expression'

Motivation: In some cases, it is helpful to generate all possible strings that match a regular expression and join them together with a custom delimiter for further processing or displaying.

Explanation: The --delimiter flag specifies the delimiter string to be used when joining the generated strings.

Example output: For the regular expression [0-9]{2}, the command exrex --delimiter ", " '[0-9]{2}' will generate all possible two-digit numbers and join them with a comma and a space delimiter, resulting in the output 00, 01, 02, 03, ..., 99.

Use case 5: Print count of all possible strings that match a regular expression

Code:

exrex --count 'regular_expression'

Motivation: Obtaining the count of all possible strings that match a regular expression can be helpful to estimate the number of matches or understand the complexity of the regular expression.

Explanation: The --count flag prints the count of all possible strings that match the given regular expression.

Example output: For the regular expression [A-Za-z]{3}, the command exrex --count '[A-Za-z]{3}' will output 26^3 = 17,576, indicating that there are 17,576 possible three-letter combinations using uppercase and lowercase letters.

Use case 6: Simplify a regular expression

Code:

exrex --simplify 'ab|ac'

Motivation: Regular expressions can sometimes become complex and hard to read. Simplifying a regular expression allows for easier understanding and maintenance.

Explanation: The --simplify flag simplifies the given regular expression.

Example output: For the regular expression ab|ac, the command exrex --simplify 'ab|ac' will output a[b|c], which represents a choice between ab and ac in a simplified form.

Additional use cases

In addition to the main use cases provided above, the ’exrex’ command can also be used for more playful purposes, such as printing eyes or a boat.

Code:

exrex '[oO0](_)[oO0]'

Explanation: The regular expression [oO0](_)[oO0] matches patterns like o_o or 0_0, which resemble eyes.

Code:

exrex '( {20}(\| *\\|-{22}|\|)|\.={50}| ( ){0,5}\\\.| {12}~{39})'

Explanation: The regular expression ( {20}(\| *\\|-{22}|\|)|\.={50}| ( ){0,5}\\\.| {12}~{39}) matches patterns that resemble the shape of a boat when displayed.

Conclusion

The ’exrex’ command is a versatile tool for generating and simplifying regular expressions. Whether it is for testing, data generation, or exploring different string patterns, ’exrex’ provides a convenient way to work with regular expressions and their matches.