Core Function Regex Match
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=== Remarks === | === Remarks === | ||
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| + | Note - The below is only for single matches not flag "g" matches. | ||
If a regular expression pattern is matched correctly and it has capture groups in the pattern the groups will be set to local variables for example: | If a regular expression pattern is matched correctly and it has capture groups in the pattern the groups will be set to local variables for example: | ||
Revision as of 16:27, 19 November 2011
<Expression> =~ m/pattern/flags
Contents |
Description
Match a string to a regular expression pattern and check if it matches and optionally return captured groups
Parameters
Expression
Any valid expression that is a string.
pattern
The regular expression pattern to match.
flags
Optional; The flags to use in the pattern.
i = Ignore case.
m = Treat the string as multiple lines.
s = Treat the string as a single line.
o = Do not recompile the regular expression after the first compile (Improves speed of your matches if you run the pattern many times).
g = Match all occurances of the pattern in the string (Default is only match the first).
d = Return a single dimension array when using flag "g" (Default is to return a multi-dimension array).
Note - If flag "g" is used the $_rg array will contain all matches from first to last it will not contain the text it matched it will only contain the matches, However if "g" is not used then the first element will be the matched text followed by all the matched groups 1 2 3 4 etc.
Return Value
Success: Returns 1 if the match was successful.
Failure: Returns 0.
Remarks
Note - The below is only for single matches not flag "g" matches.
If a regular expression pattern is matched correctly and it has capture groups in the pattern the groups will be set to local variables for example:
Group 0 will be $0.
Group 1 will be $1.
Group 2 will be $2.
And so on.
Of course captured NAMED groups will also be returned as follows:
Named group "Test" will be $_rg["Test"]
Named group "Moo" will be $_rg["Moo"]
Named group "Cat" will be $_rg["Cat"]
And so on.
After each regular expression match all capture groups from the previous match will be deleted so its best to copy them if you intend to keep using them.
Example
Check if a string matches a given pattern :
// Set a string to parse $str = "Hello, World!"; if( $str =~ m/\w+,\s+\w+!/ ) { println("True"); } else { println("False"); }
Check if a string matches a given pattern case insensitive :
// Set a string to parse $str = "Hello, World!"; if( $str =~ m/hello,\s+WORLD!/i ) { println("True"); } else { println("False"); }
Simple matching a string and returning 2 captured groups :
// Set a string to parse $str = 'Account Test Credits 777'; // Do the regex match $str =~ m/Account\s+(\w+)\s+\w+\s+(\d+)/i; println("Account '$1' Credits '$2'"); // Prints // Account 'Test' Credits '777'
Simple matching a string and returning 2 captured groups and saving the variables:
// Set a string to parse $str = 'Account Test Credits 777'; // Do the regex match $str =~ m/Account\s+(\w+)\s+\w+\s+(\d+)/i; $Account = $1; $Credits = $2; println("Account '$Account' Credits '$Credits'"); // Prints // Account 'Test' Credits '777'
Same thing but this time parsing multiple lines of accounts :
// Set a string to parse $str = 'Account Test Credits 777' . @CRLF; $str .= 'Account FoX Credits 1337' . @CRLF; $str .= 'Account Cat Credits 100' . @CRLF; $str .= 'Account Dog Credits 50' . @CRLF; // Do the regex match $str =~ m/Account\s+(\w+)\s+\w+\s+(\d+)/ig; // Print them all for($i = 0; $i < @Groups; $i++) { $Account = $_rg[$i, 1]; $Credits = $_rg[$i, 2]; println("Match ($i) | Account '" . $Account . "' | Credits '" . $Credits . "'" ); } // Prints // Match (0) | Account 'Test' | Credits '777' // Match (1) | Account 'FoX' | Credits '1337' // Match (2) | Account 'Cat' | Credits '100' // Match (3) | Account 'Dog' | Credits '50'
Case insensitive match on a string to capture all possible matches and return them as a multi-dimensional array :
// Set a string to parse $str = '<test>a</test> <test>b</test> <test>c</Test>'; // Do the regex match $str =~ m/<(?i)test>(.*?)</(?i)test>/ig; // How many groups did we find? println("Found groups: " . @Groups); // Print them all for($i = 0; $i < @Groups; $i++) { $match = $_rg[$i]; println("Match ($i) | Text '" . $match[0] . "' | Group text '" . $match[1] . "'" ); } // Prints // Found groups: 3 // Match (0) | Text '<test>a</test>' | Group text 'a' // Match (1) | Text '<test>b</test>' | Group text 'b' // Match (2) | Text '<test>c</Test>' | Group text 'c'
Case insensitive match on a string to capture all possible matches and return them as a single dimension array :
// Set a string to parse $str = '<test>a</test> <test>b</test> <test>c</Test>'; // Do the regex match $str =~ m/<(?i)test>(.*?)</(?i)test>/igd; // How many groups did we find? println("Found groups: " . @Groups); // Print them all for($i = 0; $i < @Groups; $i++) { println("Match ($i) | Group text '" . $_rg[$i] . "'" ); } // Prints // Found groups: 3 // Match (0) | Group text 'a' // Match (1) | Group text 'b' // Match (2) | Group text 'c'
