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.
Item Description
Syntax substr(s, i, j)
Description Extracts parts from a string.
Parameter
  • s: the string that you want to extract.
  • 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.
Item 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
//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'))
}

upper

The following table describes the details about this function.
Item 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
//Output:
//HELLO,DSL
//hello, dsl

mystr = 'Hello, Dsl'                                                                                                                                                                                   
say(upper(mystr))                                                                                                                                                                                      
say(lower(mystr)) 

lower

The following table describes the details about this function.
Item 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
//Output:
//HELLO,DSL
//hello, dsl

mystr = 'Hello, Dsl'                                                                                                                                                                                   
say(upper(mystr))                                                                                                                                                                                      
say(lower(mystr)) 

len

The following table describes the details about this function.
Item 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
//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'))
}

byte

The following table describes the details about this function.
Item 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
//Output: 97
//65

say(byte('a'))
say(byte('A'))

match_re

The following table describes the details about this function.
Item Description
Syntax match_re(s, p [, o])
Description Uses the Perl Compatible Regular Expressions (PCRE) engine for regular expression matching.
Parameter
  • s: the string that you want to match. Data type: string.
  • p: the regular expression. Data type: string.
  • o: the regular expression engine. Data type: string. This parameter is optional.
  • 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
url = concat('http://', $host, $uri)
m1 = match_re(url, 'http://.*\.dslex\.com/.*')
m2 = match_re(url, '^http://.*\.alibaba\.com\.cn/.*\.d\\.html(\?.*)?$')
m3 = match_re(url, '^http://.*.test.dslex.com/.*\.d\.html(\?.*)?$')
m4 = match_re(url, '^http://.*\.alibaba\.com\.cn/zt_d/')
m5 = match_re(url, '^http://tech.alibaba.com.cn/zt_d/we2015/?$')
m6 = match_re($args, 'from=wap1$')
m7 = match_re($args, 'from=comos1$')

if and(m1, or(m2, m3), not(m4), not(m5), or(not(m6), not(m7))) {                                                                                                                                       
    add_rsp_header('USER-DEFINED-1', 'hit1')                                                                                                                                                           
    add_rsp_header('USER-DEFINED-2', 'hit2')                                                                                                                                                         

capture_re

The following table describes the details about this function.
Item Description
Syntax capture_re(s, p [,init])
Description Captures the matches of a string and returns the matching substrings. The PCRE engine is used.
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)
}                                                                                                                                                      

gsub_re

The following table describes the details about this function.
Item Description
Syntax gsub_re(subject, regex, replace [,option])
Description Replaces all matches of a string and returns the string after the replacement. The PCRE engine is used.
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
//Output:
//X-DEBUG-GSUB-RE: [Hello,H], [Es,E]

subject = 'Hello, Es'
regex = '([a-zA-Z])[a-z]+'
replace = '[$0,$1]'
add_rsp_header('X-DEBUG-GSUB-RE', gsub_re(subject, regex, replace))                                                                                                                                               
References:

For more information about PCRE, see pcre2syntax man page.

split

The following table describes the details about this function.
Item 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
//Request: ?from=xx1,xx2,xx3  
//Response: [1]=xx1  
//[2]=xx1

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)))
    }
}                                                                                                                                            

split_as_key

The following table describes the details about this function.
Item 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 values in the same way as the split() function. However, the key parameter is named after each split element: Element 1 -> Element 2.
Example
//Request: ?from=xx1,xx2,xx3  
//Response: xx2=xx2 u=hi,dsl
//xx1=xx1 u=hi,dsl
//xx3=xx3 u=hi,dsl     

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'])
}                                                                                                                                     

tohex

The following table describes the details about this function.
Item 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
//Note: A response header is added.
//X-DSL-TOHEX: 4ad583af22c2e7d40c1c916b2920299155a46464     

digest = sha1('xxxx')
add_rsp_header('X-DSL-TOHEX', tohex(digest))                                                                                                                                        

tostring

The following table describes the details about this function.
Item 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
//Note: A response header is added.
//X-DSL-TOSTRING: 123    

s = tostring(123)
add_rsp_header('X-DSL-TOSTRING', s)                                                                                                                              

tochar

The following table describes the details about this function.
Item 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
//Output: A response header is added.
//X-DSL-TOCHAR: a
//X-DSL-TOCHAR: ab

add_rsp_header('X-DSL-TOCHAR', tochar(97))
add_rsp_header('X-DSL-TOCHAR', tochar(97, 98), true)

//Output: A response header is added.
//Content-Disposition: attachment;filename="The value of the filename parameter"   

if $arg_filename {
    hn = 'Content-Disposition'
    add_rsp_header('Content-Disposition', concat('attachment;filename=', tochar(34), filename, tochar(34)))
    add_rsp_header(hn, hv)
}                                                                                                                                      

reverse

The following table describes the details about this function.
Item 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.
Item Description
Syntax string.find (s, substr, pos)
Description Searches for the specified content in a specified string. The third parameter is used as the index.
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 content 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 content is not found.
Example
 str = 'hello dsl'
 add_rsp_header('string-find()-start', tostring(get(find(str, 'dsl'), 1)))
 str = 'hello dsl 12'
 add_rsp_header('string-find()-end', tostring(get(find(str, 'dsl'), 2)))
 str = 'hello dsl'
 add_rsp_header('string-find()-tail-start', tostring(get(find(str, 'dsl', -6), 1)))
 str = 'hello dsl 12'
 add_rsp_header('string-find()-tail-end', tostring(get(find(str, 'dsl', -6), 2)))
Output:
string-find()-start:7
string-find()-end:9
string-find()-tail-start:7
string-find()-tail-end:9

format

The following table describes the details about this function.
Item 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.
Item 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.
Item 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