String functions - CDN - Alibaba Cloud Documentation Center

This topic describes the syntax, description, parameters, and return values of string functions. This topic also provides examples of these functions.

substr

The following table describes the details about this function.

Feature	Description
Syntax	`substr(s, i, j)`
Description	Extracts parts from a string.
Parameter	s: the source string. i: the position to start extraction in the source string, counting from 1. A value of -1 specifies the rightmost character of the string. Data type: integer. j: the position to end extraction in the source string, counting from 1. A value of -1 specifies the rightmost character of the string. Data type: integer.
Return value	Returns a substring `s[i, j]` that is extracted from the source string specified by `s`.
Example	`//Note: The two methods that are used to determine whether a file is an M3U8 file. if eq(substr($uri, -5, -1), '.m3u8') { say(concat($uri, ' is .m3u8')) } uri_len = len($uri) if eq(substr($uri, -5, uri_len), '.m3u8') { say(concat($uri, ' is .m3u8')) }`

concat

The following table describes the details about this function.

Feature	Description
Syntax	`concat(s1, ...)`
Description	Concatenates strings.
Parameter	The strings that you want to concatenate. You can specify one or more strings. Numeric values are supported.
Return value	Returns a concatenated string.
Example	`// Concatenates the following strings str1 = 'hello' str2 = ' ' str3 = 'world' say(concat(str1, str2, str3))` Output: `hello world`

upper

The following table describes the details about this function.

Feature	Description
Syntax	`upper(s)`
Description	Converts a string to uppercase letters.
Parameter	s: the string that you want to convert.
Return value	Returns the string specified by the `s` parameter in uppercase letters.
Example	`str = 'hello world' say(upper(str))` Output: `HELLO WORLD`

lower

The following table describes the details about this function.

Feature	Description
Syntax	`lower(s)`
Description	Converts a string to lowercase letters.
Parameter	s: the string that you want to convert.
Return value	Returns the string specified by the `s` parameter in lowercase letters.
Example	`str = 'HELLO WORLD' say(lower(str))` Output: `hello world`

len

The following table describes the details about this function.

Feature	Description
Syntax	`len(s)`
Description	Queries the length of a string.
Parameter	s: the string that you want to measure.
Return value	Returns the length of the string specified by the `s` parameter. Data type: integer.
Example	`str = 'hello world' say(len(str)) // Returns the length of str. Here is 11.`

byte

The following table describes the details about this function.

Feature	Description
Syntax	`byte(c)`
Description	Queries the ASCII value of a character.
Parameter	c: the character whose ASCII value you want to query. You can specify only one character.
Return value	Returns the ASCII value of the specified character. Data type: numeric.
Example	`say(byte('a')) say(byte('A'))` Output: `97 65`

match_re

The following table describes the details about this function.

Feature	Description
Syntax	`match_re(s, p [, o])`
Description	Uses the Perl Compatible Regular Expressions (PCRE) engine for regular expression matching. For more information, see PCRE syntax.
Parameter	s: the string that you want to match. Data type: string. p: the regular expression for matching. Data type: string. o: the regular expression engine. Data type: string. This parameter is optional. empty value: specifies that this function is case-sensitive. i: specifies that this function is not case-sensitive.
Return value	If the string matches the regular expression, `true` is returned. Otherwise, `false` is returned.
Example	`str = 'Hello' // An exact match with "Hello" say(match_re(str, 'Hello')) // A case-insensitive match with "Hello" say(match_re(str, 'hello', i)) // Matches any string that ends with the letter "l" say(match_re(str, '.*l$'))` Output: `true true false`

capture_re

The following table describes the details about this function.

Feature	Description
Syntax	`capture_re(s, p [,init])`
Description	Captures the matches of a string and returns the matching substrings. For more information about PCRE, see PCRE syntax.
Parameter	s: the string that you want to match. Data type: string. p: the regular expression for matching. Data type: string. init: the position to start matching, counting from 1. Data type: integer.
Return value	Returns the matching substrings in the dictionary type if the string matches the regular expression. Otherwise, an empty dictionary is returned.
Example	`pcs = capture_re($request_uri,'^/([^/]+)/([^/]+)([^?]+)\?(.*)') sec1 = get(pcs, 1) sec2 = get(pcs, 2) sec3 = get(pcs, 3) if or(not(sec1), not(sec2), not(sec3)) { add_rsp_header('X-TENGINE-ERROR', 'auth failed - missing necessary uri set') exit(403) } digest = md5(concat(sec1, sec3)) if ne(digest, sec2) { add_rsp_header('X-TENGINE-ERROR', 'auth failed - invalid digest') exit(403) }`
Response example	`"X-TENGINE-ERROR:auth failed - missing necessary uri set"`

gsub_re

The following table describes the details about this function.

Feature	Description
Syntax	`gsub_re(subject, regex, replace [,option])`
Description	Replaces all matches of a string and returns the string after the replacement. For more information about PCRE, see PCRE syntax.
Parameter	subject: the string that you want to match. Data type: string. regex: the regular expression. Data type: string. replace: the string for replacement. Data type: string. You can specify the `replace` parameter by using the matching substrings. $0: specifies all substrings that match `regex`. $N: specifies the substring that matches the Nth parenthesized subexpression `()` of `regex`. option: the regular expression engine. Data type: string. This parameter is optional.
Return value	Replaces all substrings that match the specified `regex` parameter in the specified `subject` parameter with those specified by the `replace` parameter and returns the string after the replacement.
Example	`subject = 'Hello, Es' regex = '([a-zA-Z])[a-z]+' replace = '[$0,$1]' add_rsp_header('X-DEBUG-GSUB-RE', gsub_re(subject, regex, replace))`
Response example	`"X-DEBUG-GSUB-RE:[Hello,H], [Es,E]"`

split

The following table describes the details about this function.

Feature	Description
Syntax	`split(s [,sep])`
Description	Splits a string into an array of substrings and returns the array.
Parameter	s: the string that you want to split. Data type: string. sep: the separator that is used to split the string. Data type: string.
Return value	Returns an array of key-value pairs in the dictionary type. The value of the `key` parameter is a number that starts from 1, for example, [1]=xx and [2]=y. If `sep` is left empty, the string is split by whitespace characters. Whitespace characters include space characters and tab characters (\t).
Example	`if $arg_from { t = split($arg_from, ',') if get(t, 1) { say(concat('[1]=', get(t, 1))) } if get(t, 2) { say(concat('[2]=', get(t, 1))) } }` Request: `http://www.example.com?from=xx1,xx2,xx3` Output: `[1]=xx1 [2]=xx1`

split_as_key

The following table describes the details about this function.

Feature	Description
Syntax	`split_as_key(s [,sep])`
Description	Splits a string into an array of substrings and returns the array.
Parameter	s: the string that you want to split. Data type: string. sep: the separator that is used to split the string. Data type: string.
Return value	Returns response parameters in the same way as the `split()` function. However, the `key` parameter is named after each split element: `Element 1` -> `Element 2`.
Example	`def echo_each(k, v, u) { s = concat(k, '=', v, ' u=', get(u, 1)) say(s) } if $arg_from { t = split_as_key($arg_from, ',') foreach(t, echo_each, ['hi,dsl']) }` Request: `http://www.example.com?from=xx1,xx2,xx3` Output: `xx2=xx2 u=hi,dsl xx1=xx1 u=hi,dsl xx3=xx3 u=hi,dsl`

tohex

The following table describes the details about this function.

Feature	Description
Syntax	`tohex(s)`
Description	Converts a string to a hexadecimal string.
Parameter	s: the string that you want to convert.
Return value	Returns a hexadecimal string that is converted from the string specified by the `s` parameter.
Example	`digest = sha1('xxxx') add_rsp_header('X-DSL-TOHEX', tohex(digest))`
Response example	`"X-DSL-TOHEX: 4ad583af22c2e7d40c1c916b2920299155a46464"`

tostring

The following table describes the details about this function.

Feature	Description
Syntax	`tostring(a)`
Description	Converts data of any type to a string.
Parameter	a: the data that you want to convert. Data type: any type.
Return value	Returns a string that is converted from the value specified by the `a` parameter.
Example	`say(tostring(123))` Output: `123`

tochar

The following table describes the details about this function.

Feature	Description
Syntax	`tochar(n1, n2, ...)`
Description	Converts one or more internal integers (ASCII values) to a string. For example, 48 corresponds to the character "0". The length of the returned string is based on the number of specified parameters.
Parameter	nX: the integers that you want to convert. You can specify one or more integers.
Return value	Returns a string that is converted from integers.
Example	`say(tochar(97)) say(tochar(65))` Output: `a A`

reverse

The following table describes the details about this function.

Feature	Description
Syntax	`reverse(str)`
Description	Reverses a string.
Parameter	str: the string that you want to reverse.
Return value	Returns a string reversed from the specified string.
Example	`say(reverse('hello'))` Output: `olleh`

find

The following table describes the details about this function.

Feature	Description
Syntax	`string.find (s, substr, pos)`
Description	Searches for a substring in a specified string.
Parameter	s: the string that you want to search. substr: the substring that you want to search. pos: the position where the search starts. Data type: numeric. This parameter is optional. You can specify a negative integer. The default value is 1.
Return value	Returns an array if the specified substring is found. Index 1 indicates the position where the search starts. Index 2 indicates the position where the search ends. Returns an empty array if the specified substring is not found.
Example	`str = 'hello world' say(concat('r start pos: ',get(find(str, 'r'), 1))) say(concat('r end pos: ',get(find(str, 'r'), 2))) say(concat('rl start pos: ',get(find(str, 'rl'), 1))) say(concat('rl end pos: ',get(find(str, 'rl'), 2)))` Output: `r start pos: 9 r end pos: 9 rl start pos: 9 rl end pos: 10`

format

The following table describes the details about this function.

Feature	Description
Syntax	`format(fmt, ···)`
Description	Formats the values of one or more parameters. The format string is the first parameter, which must specify a string. The format string follows the specification of the sprintf parameter used by functions in the C programming language. The syntax of a format string is: %[parameter][flag][field width][.precision]specifier. %%: prints literal percentage signs (%). %c: converts integers into ASCII characters. %d: coverts integers into decimal numbers. %f: converts N-precision numbers into floating point numbers. %o: converts integers into octal numbers. %s: converts integers into strings. %x: converts integers into hexadecimal numbers in lowercase letters. %X: converts integers into hexadecimal numbers in uppercase letters.
Parameter	fmt: the string type. This parameter specifies a format string. The variable number of parameters: any type.
Return value	Returns an ACSII string.
Example	`say(concat('format:', format('%%%s$%.2s$%s$%c$%d$%2.2f$%.2o$%x$%X', 'format', 3.1415926, true, 95, 3.1415926, 3.1415926, 3.1415926, 10, 10)))` Output: `format:%format$3.$true$_$3$3.14$03$a$A`

tobin

The following table describes the details about this function.

Feature	Description
Syntax	`tobin(str)`
Description	Converts a hexadecimal string to an ASCII string.
Parameter	str: the hexadecimal string that you want to convert. It is not case-sensitive.
Return value	Returns an ACSII string.
Example	`say(concat('tobin:', tobin('2F2F')))` Output: `tobin://`

trim

The following table describes the details about this function.

Feature	Description
Syntax	`trim(s, [, loc])`
Description	Removes all whitespace characters before or after the string specified by the s parameter, and returns a string with the specified whitespace characters removed.
Parameter	s: the string. loc: the default value is both. This parameter is optional. Valid values: both: removes the whitespace characters before and after the string. left: removes only the whitespace characters before the string. right: removes only the whitespace characters after the string.
Return value	Returns a string with the specified whitespace characters removed.
Example	`say(concat('trim():', trim(' abcd '))) say(concat('trim(left):', trim(' abcd', 'left'))) say(concat('trim(right):', trim('abcd ', 'right')))` Output: `trim():abcd trim(left):abcd trim(right):abcd`