Regex Matches (rx)

Regexp pattern matching for file system objects (eg .*\\.txt)

Description

Returns a list of files and directories that match a regexp pattern.

Output is a JSON list.

Usage

rx pattern -> <stdout>

!rx pattern -> <stdout>

<stdin> -> rx pattern -> <stdout>

<stdin> -> !rx pattern -> <stdout>

Examples

Inline regex file matching

cat: @{ rx '.*\.txt' }

Writing a list of files to disk

rx '.*\.go' |> filelist.txt

Checking if files exist

if { rx somefiles.* } then {
    # files exist
}

Checking if files do not exist

!if { rx somefiles.* } then {
    # files do not exist
}

Return all files apart from

!rx '\.txt$'

Filtering a file list

Filtering a file list, returning only files that match the regexp match:

f +f -> rx '.*\.txt'

Please note that rx here is doing an additional check if the file exists.

Remove any regexp file matches

f +f -> !rx '.*\.txt'

Detail

Traversing Directories

Unlike globbing (g) which can traverse directories (eg g /path/*), rx is only designed to match file system objects in the current working directory.

rx uses Go (lang)’s standard regexp engine.

Inverse Matches

If you want to exclude any matches based on wildcards, rather than include them, then you can use the bang prefix. eg

» rx READ*                                                                                                                                                              
[
    "README.html"
]

murex-dev» !rx .*
Error in `!rx` (1,1): No data returned.

When Used As A Method

!rx first looks for files that match its pattern, then it reads the file list from stdin. If stdin contains contents that are not files then !rx might not handle those list items correctly. This shouldn’t be an issue with rx in its normal mode because it is only looking for matches however when used as !rx any items that are not files will leak through.

This is its designed feature and not a bug. If you wish to remove anything that also isn’t a file then you should first pipe into either g *, rx .*, or f +f and then pipe that into !rx.

The reason for this behavior is to separate this from !regexp and !match.

Synonyms

See Also

This document was generated from builtins/core/io/rx_doc.yaml.

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Last built on Wed Jul 2 22:12:32 UTC 2025 against commit bb72b6fbb72b6fdd502f835172d7d06207ba4ec2c70886c.

Current version is 7.0.2107 (develop) which has been verified against tests cases.