Most of the data manipulation you'll do with TrafficScript will involve manipulating strings. Here is a quick account of the most useful string functions.
Strings are managed efficiently within the TrafficScript runtime engine, and memory copies are kept to a minimum.
Creating and concatenating strings
Assign a string to a variable:
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$password = "Secret"; |
Many functions take strings as arguments, and return strings as values:
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$host = http.getHeader( "Host" ); |
Concatenate strings with the '.' operator:
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$greeting = "Hello, ".$name; $link = "<a href=\"".$url."\">Click here";<a> |
Basic string functions
The length of a string:
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$len = string.len( $mystring ); |
Skip or drop bytes off the start or end of a string:
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$interpreter = "#!/bin/sh"; $str = string.skip( $interpreter, 2 ); # returns "/bin/sh" $greeting = "Hello, world!..."; $msg = string.drop( $greeting, 4 ); # returns "Hello, world" |
Remove whitespace from the start and end of a string:
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The string.substring() function returns a substring from a string:
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$time = "09:15:45"; $hr = string.substring( $time, 0, 2 ); # returns "09" $min = string.substring( $time, 3, 2 ); # returns "15" $sec = string.substring( $time, 6, 2 ); # returns "45" |
String tests
The following functions test the contents of a string:
The string.find() function searches for a substring and returns its location:
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$greeting = "Hello, world!"; $i = string.find( $greeting, "llo" ); # returns 2 $j = string.find( $greeting, "Hello" ); # returns 0 $k = string.find( $greeting, "name" ); # returns -1 (not found) |
String compares can be performed with the '==', '!=', '<', '>', '<=' and '>=' operators:
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if( $protocol <= "1.0" ) { ... } |
Note that TrafficScript's Type Casting Rules can affect the behaviour of a compare operation:
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$count = "100"; # Do a string compare if( $protocol < "99" ) { ... } # Do an integer compare if( $protocol < 99 ) { ... } |
The string.cmp() and string.icmp() functions perform case sensistive and case insensitive string compares, returning negative, zero or positive values. Both arguments are converted to strings if necessary:
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if( string.cmp( $protocol, "1.0" ) < 0 ) { ... } # This is identical if( string.icmp( $protocol, 1.0 ) < 0 ) { ... } |
String matching and substitution
The string.wildmatch() function performs a shell-like wildcard match on a string. The character '?' matches any single character, and '*' matches any substring:
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$url = http.getPath(); if( string.wildmatch( $url, "/cgi-bin/*.cgi" ) ) { ... # is a request for a CGI script, without pathinfo } |
Regular expression matching can be performed with the string.regexMatch() function. Stingray uses the standard PCRE regular expression syntax, and matches are placed in the magic $1 to $9 variables:
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$id = "user=Joe, password=Secret"; if( string.regexmatch( $id, "^user=(.*), password=(.*)$" ) ) { log.info( "Got UserID: ".$1.", Password: ".$2 ); } |
Perform case-insensitive regular expression matches using the optional third function argument:
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string.regexmatch( $username, "joe", "i" ); |
Regular expression substitutions are the easiest and most powerful way to perform complex string manipulation. Text in a string which matches the regular expression is replaced by the substitution:
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# Rewrite requests for "/secure/something" to "/private/something" $url = string.regexsub($url, "^/secure", "/private"); |
Normally, only the first match is replaced; the optional "g" flag indicates that a 'global' replace should be performed, where every match is replaced.
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# The document contains references to "oldsite.example.com"; # replace these with "newsite.enterprise.com" $response = http.getResponseBody(); $response = string.regexsub( $response, "oldsite.example.com", "newsite.example.com", "g" ); http.setResponseBody( $response ); |
String encoding and decoding
Convert between case using string.toUpper() and string.toLower():
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$string = "AbCdEfG"; $upper = string.toUpper( $string ); # returns "ABCDEFG" $lower = string.toLower( $string ); # returns "abcdefg" |
HTML-encode a string for safe rendering in a browser using string.htmlEncode(); use string.htmlDecode() to reverse the operation:
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$xss = "<script type="mce-no/type">// alert('Hello!');// </script>"; # This returns "<script>alert('Hello!');</script>" $safe = string.htmlencode( $xss ); |
%-encode control characters, spaces and '%' in a string using string.escape(); use string.unescape() to reverse the operation:
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# returns "Hello%20World!%0D%0A" $str = string.escape( "Hello World!\r\n" ); |
You may want to manually replace incidences of "&", "?" and "=" with their %-encoded counterparts if you want to use the result in a URL.
Use Base64 encoding for a more universal encoding scheme: string.base64encode() and string.base64decode() encode and decode strings. Base64 is used for MIME-encoded messages, and in the HTTP Basic Authorization header.
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# Encodes a username and password for HTTP BASIC authentication $enc = string.base64encode( "user ); http.setHeader( "Authorization", "Basic ".$enc ); |
asswd"
An alternative pair of functions would be string.hexEncode() and string.hexDecode().
Finally, you can encrypt and decrypt strings using a passphrase and the AES cipher:
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$encrypted = string.encrypt( $plaintext, $passphrase ); $plaintext = string.decrypt( $encrypted, $passphrase ); |
Read more: Collected Tech Tips: TrafficScript examples
