Design

Back Next

replace

The replace function in XQuery is used to replace parts of a string that match a specified regular expression with a replacement string. This function is highly useful for string manipulation tasks such as text sanitation, formatting, and transformation.

Syntax

fn:replace(input, pattern, replacement, flags)

The following table describes the argument for this command:

Argument	Required/Optional	Description
input	Required	The input string to be processed. If this argument is an empty sequence ( () ), it is treated as an empty string.
pattern	Required	A regular expression pattern that specifies what part of the input string to replace. The pattern must be a valid regular expression.
replacement	Required	The string that will replace each substring of the input string that matches the regular expression pattern. Special replacement strings, such as $1 , can be used to refer to captured groups within the pattern.
flags		A string of flags that modify the behavior of the regular expression as follows: s : Single-line mode, where the dot (.) matches all characters, including newline. m : Multi-line mode, where start ^ and end $ anchors match the start and end of any line. i : Case-insensitive mode.

Return Value

Returns the

xs:string

that is obtained by replacing each non-overlapping substring of

$input

that matches the given

$pattern

with an occurrence of the

$replacement

string.

If no portions match, the original string is returned unchanged.

Examples

The following table lists some sample values and return values:

SAMPLE FUNCTION	OUTPUT
fn:replace('query', 'r', 'as')	queasy
fn:replace('query', 'qu', 'quack')	quackery
fn:replace('query', '[ry]', 'l')	quell
fn:replace('query', '[ry]+', 'l')	quel
fn:replace('query', 'z', 'a')	query
fn:replace('query', 'query', '')	zero-length string
fn:replace( (), 'r', 'as')	zero-length string
fn:replace('query', 'r?', 'as')	Error FORX0003
fn:replace('query', '(r', 'as')	Error FORX0002
fn:replace('Chapter', '(Chap)\|(Chapter)', 'x')	xter

The following examples show the difference between reluctant and regular quantifiers:

SAMPLE FUNCTION	OUTPUT
fn:replace('reluctant', 'r.*t', 'X')	X
fn:replace('reluctant', 'r.*?t', 'X')	Xant
fn:replace('aaah', 'a{2,3}', 'X')	Xh
fn:replace('aaah', 'a{2,3}?', 'X')	Xah
fn:replace('aaaah', 'a{2,3}', 'X')	Xah
fn:replace('aaaah', 'a{2,3}?', 'X')	XXh

The following examples exhibit the use of sub-expressions:

SAMPLE FUNCTION	OUTPUT
fn:replace('Chap 2...Chap 3...Chap 4...', 'Chap (\d)', 'Sec $1.0')	Sec 2.0...Sec 3.0...Sec 4.0...
fn:replace('abc123', '([a-z])', '$1x')	axbxcx123
fn:replace('2315551212', '(\d{3})(\d{3})(\d{4})', '($1) $2-$3')	(231) 555-1212
fn:replace('2006-10-18', '\d{2}(\d{2})-(\d{2})-(\d{2})', '$2/$3/$1')	10/18/06
fn:replace('25', '(\d+)', '\$$1.00')	$25.00