A matcher looks at some text, in the context of a pattern, and states yes or no : that text matches this pattern.
A matcher is specified with a period delimited list, consiting of a method and some modifiers. An empty specification indicated a case sensitive regex over plain bytes.
A matcher is commonly used as a single comma delimited parameter : Matcher,Pattern (e.g. cat) or Column,Matcher,Pattern (e.g. cgrep).
In both cases it’s fine for the Pattern to contain commas. Modifers and methods are not case sensitive.
## Modifiers :
* utf8 - String : operations are on utf8 strings, rather than the default u8 bytes
* not - Negate : treat a match as a non-match, and vice versa.
* case - Case Insensitive : ignore case. Exact behavior depends on "S"
* trim - remove leading and trailing whitespce before checking
* null - an empty string also matches. This check happens after trimming.
* and - See Multi-Match below. Matches if all pattern match.
* or - See Multi-Match below. Matches if any pattern matches.
If you do not specify ‘S’ in the modifiers, then matching against non-utf8 field values is OK.
## Methods :
* regex - A regex as per the eponymous crate
* expr - a floating point expression, that must be non-zero, e.g. `price>100.0`
* exact - An exact match
* prefix - The pattern is a prefix of the field value
* suffix - The pattern is a suffix of the field value
* infix - The pattern is a contained in the field value.
* file-exact - The pattern is a file name. The field value exactly matches one of the lines in the file.
* glob - The pattern is a shell-style glob pattern, like `*.txt`
* length - The pattern is either one number, or two comma delimited numbers. The first number if the minumim string length, the second is the inclusive maximum.
* empty - Matchs only the empty string. Pattern is ignored. The same as `length` if you specified `0,0` as the pattern.
* blank - Matches a string composed enirely of whitespace. A superset of `empty`.
* hash - Matches a string starting with whitespace, followed by `#`. Pattern is ignored. A superset of `blank`.
* slash - Matches a string starting with whitespace, followed by `//`. Pattern is ignored. A superset of `blank`.
* yes - Always matches. Use `yes.N` for something that never matches.
A normal match is Matcher,Pattern
A multi-match contains multiple patterns. If the Modifiers contains AND or OR, then the first character of the pattern is interpreted as a delimiter, and the Pattern string is split on that delimiter, into multiple patterns. e.g.
c.or.regex,,Pattern,Pattern,Pattern or Column,AND,^Pattern^Pattern^Pattern