Building RegEx expressions

In IBM® Cloud Logs, you can use parsing rules to control the structure of your data by applying RegEx expressions before the data is indexed for search.

IBM Cloud Logs uses the RegEx Golang flavor.

A RegEx pattern is case-sensitive.

Quantifiers

Quantifiers
Quantifier	Matches
`*`	0 or more matches of the previous character or sequence.
`?`	0 or 1 matches of the previous character or sequence.
`+`	1 or more matches of the previous character or sequence.
`{N}`	Matches exactly N times the previous character.
`{N,}`	Matches N or more times the previous character.
`{N,Z}`	Matches between N and Z times the previous character.

Characters

Characters
Characters	Matches
`.`	Matches any single character.
`.*`	Matches anything.
`\d`	Matches 1 single digit.
`\d*`	Matches N digits.
`\D`	Matches any symbol except digits.
`\w`	Matches any letter, digit, or underscore.
`\W`	Matches any character that is not a letter, digit, or underscore.
`\s`	Matches a whitespace character.
`\S`	Matches any character except space, tab, newline or carriage return.
`\s*`	Matches N whitespace characters.
`\S`	Matches any character that is not whitespace.
`\S*`	Matches N characters that are not whitespace.

Anchors

Anchors
Anchors	Matches
`\b`	Defines a word boundary.
`^`	Matches the start of a string or line.
`$`	Matches the end of a string or line.

Groupings

Groupings
Grouping	Matches
`[ ]`	Represents a group of characters.
`( )`	Used to group patterns.
`[abcd...]`	Matches 1 character of the ones included within the square brackets.
`[a-z]`	Matches 1 character in the range of a to z.
`[^a-z]`	Matches 1 character that is not in the range of a to z.
`[....]+`	Matches 1 or more characters of the ones listed within the square brackets.
`[....]?`	Matches 1 or 0 characters of the ones listed within the square brackets.
`[^"]*`	Matches N characters except double quotes.
`[^"\s]*`	Matches N characters except double quotes and white space.
`[^.]*`	Matches 0 or more non-dots.

Named capture groups

You can use named captured groups in a RegEx expression to define new fields from existing data in the log record.

The format of a capture group is the following:

(?P<fieldName>RegularExpression)

Where

?P represents the beginning of a capture group.
fieldName must be set to the name of the field being added.
RegularExpression represents the RegEx that defines the value of the new field.

The RegEx doesn’t have to match the entire log.