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The following is a list of metacharacters that affect the position of the search: The ^ (circumflex or caret) when not used inside square brackets (where it has a diffent meaning) means look only at the beginning of the target string, for example, ^Win will not find Windows in STRING1 but ^Moz will find Mozilla.
The following is a set of iteration metacharacters (a.k.a.
An escape sequence is a way of indicating that we want to use one of our metacharacters as a literal.
In a regular expression an escape sequence involves placing the metacharacter \ (backslash) in front of the metacharacter that we want to use as a literal, for example, if we want to find (s) in the target string window(s) then we use the search expression \(s\) and if we want to find \file in the target string c:\file then we would need to use the search expression \\file (each \ we want to search for as a literal (there are 2) is preceded by an escape sequence \).
This, correctly, gives a syntax error in the RE tester - though the additional, explanatory text in the error message is misleading.
The ^ (circumflex or caret) inside square brackets negates the expression (we will see an alternate use for the circumflex/caret outside square brackets later), for example, [^Ff] means anything except upper or lower case F and [^a-z] means everything except lower case a to z.
Notes: NOTE: There are some special range values (Character Classes) that are built-in to most regular expression software and have to be if it claims POSIX 1003.2 compliance for either BRE or ERE.
These are Browser ID Strings and appear as the Apache Environmental variable HTTP_USER_AGENT (full list of Apache environmental variables).
We are going to try some simple matching against our example target strings: Note: You can also experiment as you go through the examples.