matcher

  • string
  • glob
  • regexp
  • simple patterns

Depending on the symbol at the start of the string, the matcher will use one of the supported formats.

matchershort formatlong format
string =string
glob*glob
regexp~regexp
simple patternssimple_patterns

Example:

  • * pattern: It will use the glob matcher to find the pattern in the string.

Syntax

Tip: Read ::= as is defined as.

Short Syntax
[ <not> ] <format> <space> <expr>
<not> ::= '!'
negative expression
<format> ::= [ '=', '~', '*' ]
'=' means string match
'~' means regexp match
'*' means glob match
<space> ::= { ' ' | '\t' | '\n' | '\n' | '\r' }
<expr> ::= any string
Long Syntax
[ <not> ] <format> <separator> <expr>
<format> ::= [ 'string' | 'glob' | 'regexp' | 'simple_patterns' ]
<not> ::= '!'
negative expression
<separator> ::= ':'
<expr> ::= any string

When using the short syntax, you can enable the glob format by starting the string with a *, while in the long syntax you need to define it more explicitly. The following examples are identical. simple_patterns can be used only with the long syntax.

Examples:

  • Short Syntax: '* * '
  • Long Syntax: 'glob:*'

String matcher

The string matcher reports whether the given value equals to the string.

Examples:

  • '= foo' matches only if the string is foo.
  • '!= bar' matches any string that is not bar.

String matcher means exact match of the string. There are other string match related cases:

  • string has prefix something
  • string has suffix something
  • string contains something

This is achievable using the glob matcher:

  • * PREFIX*, means that it matches with any string that starts with PREFIX, e.g PREFIXnetdata
  • * *SUFFIX, means that it matches with any string that ends with SUFFIX, e.g netdataSUFFIX
  • * *SUBSTRING*, means that it matches with any string that contains SUBSTRING, e.g netdataSUBSTRINGnetdata

Glob matcher

The glob matcher reports whether the given value matches the wildcard pattern. It uses the standard golang library path. You can read more about the library in the golang documentation, where you can also practice with the library in order to learn the syntax and use it in your Netdata configuration.

The pattern syntax is:

pattern:
{ term }
term:
'*' matches any sequence of characters
'?' matches any single character
'[' [ '^' ] { character-range } ']'
character class (must be non-empty)
c matches character c (c != '*', '?', '\\', '[')
'\\' c matches character c
character-range:
c matches character c (c != '\\', '-', ']')
'\\' c matches character c
lo '-' hi matches character c for lo <= c <= hi

Examples:

  • * ? matches any string that is a single character.
  • '?a' matches any 2 character string that starts with any character and the second character is a, like ba but not bb or bba.
  • '[^abc]' matches any character that is NOT a,b,c. '[abc]' matches only a, b, c.
  • '*[a-d]' matches any string (*) that ends with a character that is between a and d (i.e a,b,c,d).

Regexp matcher

The regexp matcher reports whether the given value matches the RegExp pattern ( use regexp.Match ).

The RegExp syntax is described at https://golang.org/pkg/regexp/syntax/.

Learn more about regular expressions at RegexOne.

Simple patterns matcher

The simple patterns matcher reports whether the given value matches the simple patterns.

Simple patterns are a space separated list of words. Each word may use any number of wildcards *. Simple patterns allow negative matches by prefixing a word with !.

Examples:

  • !*bad* * matches anything, except all those that contain the word bad.
  • *foobar* !foo* !*bar * matches everything containing foobar, except strings that start with foo or end with bar.
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