a cli tool for evaluating c++ std::regex expressions
People often avoid C++'s <regex> library due to complaints about performance and the size of generated code. However, you might find yourself in a situation where you have no choice. What if you want to quickly test how std::regex behaves, options and all, in a way that's simple to parse? As far as I know, there are no good tools dedicated to this, though there are plenty for other regex APIs.
This project contains a library that wraps all features of the std::regex API. It exposes these features in a CLI program as program arguments, and prints results in JSON for simple parsing. The ultimate goal is to make a simple web tool that helps people test std::regex even more easily.
Here's the manual output by the program:
Usage: $ cppregex text regex [options...]
cppregex is a tool for running std::regex in C++. Give the tool the text and regex, and any desired
options, and get back JSON detailing the query and results. The default behavior, if no options are
specified, is a std::regex_search of the text, using the Modified ECMAScript regular expression grammar.
All other options are disabled unless requested. The options to the program reflect the options of the
std::regex API, and can be broadly categorized into algorithm, grammar, match, and syntax options.
Algorithm options:
==================
--search Search the entire text (std::regex_search) and return all matches. [Default]
--match Attempt to match the entire text (std::regex_match) and return a match if it exists.
--replace Replace occurrences of regex matches in the text with std::regex_replace.
Grammar options:
================
Only one option can be enabled at a time. The grammar option that appears last in the argument
list will be the grammar to use.
--ecmascript Use the Modified ECMAScript regular expression grammar. [Default]
--extended Use the extended POSIX regular expression grammar.
--basic Use the basic POSIX regular expression grammar.
--awk Use the regular expression grammar used by the awk utility in POSIX.
--grep Use the regular expression grammar used by the grep utility in POSIX.
This is effectively the same as the basic option with the addition of newline
'\n' as an alternation separator.
--egrep Use the regular expression grammar used by the grep utility, with the -E option, in POSIX.
This is effectively the same as the extended option with the addition of newline
'\n' as an alternation separator in addtion to '|'.
Match options:
==============
All of the following options are disabled by default, except for 'format-default'.
In the following descriptions, [first, last) refers to the character sequence being matched.
--match-not-bol The first character in [first, last) will be treated as if it is not at the beginning of a
line (i.e. ^ will not match [first, first)).
--match-not-eol The last character in [first, last) will be treated as if it is not at the end of a
line (i.e. $ will not match [last, last)).
--match-not-bow "\b" will not match [first, first).
--match-not-eow "\b" will not match [last, last).
--match-any If more than one match is possible, then any match is an acceptable result.
--match-not-null Do not match empty sequences.
--match-continuous Only match a sub-sequence that begins at first.
--match-prev-avail --first is a valid iterator position. When set, causes match-not-bol and match-not-bow
to be ignored.
--format-default Use ECMAScript rules to construct strings in std::regex_replace.
--format-sed Use POSIX sed utility rules in std::regex_replace.
--format-no-copy Do not copy un-matched strings to the output in std::regex_replace.
--format-first-only Only replace the first match in std::regex_replace.
--format-string="" The string to use to format the text. Works similarly to printf, but you can match groups.
For regex_constants::match_flag_type::format_default:
-Characters- -Replacement-
$n n-th backreference (i.e., a copy of the n-th matched group specified with
parentheses in the regex pattern). n must be an integer value designating
a valid backreference, greater than 1, and of two digits at most.
$& A copy of the entire match
$` The prefix (i.e., the part of the target sequence that precedes the match).
$´ The suffix (i.e., the part of the target sequence that follows the match).
$$ A single $ character.
Syntax options (all disabled by default):
=========================================
--icase Character matching should be performed without regard to case.
--nosubs When performing matches, all marked sub-expressions (expr) are treated as non-marking
sub-expressions (?:expr).
--optimize Instructs the regular expression engine to make matching faster, with the potential
cost of making construction slower.
--collage Character ranges of the form "[a-b]" will be locale sensitive.
--multiline Specifies that ^ shall match the beginning of a line and $ shall match the end of a line,
if the ECMAScript engine is selected.