Validating filenames with regularexpression validator
In addition to specifying that a given pattern may occur exactly 0 or 1 time, the ?character also forces a pattern or subpattern to match the minimal number of characters when it might match several in an input string.
The constructs within regular expressions that have special meaning are referred to as metacharacters. Also, we have seen that expressions will match any instance of the pattern they describe within a larger string, but what if you only want to match the pattern exactly?
In the last five decades, regular expressions have slowly made their way from mathematic obscurity to a staple feature of many tools and software packages.
While regular expressions were supported by many UNIX tools for decades, it was only in the last decade or so that they have found their way into most Windows developers' toolkits.
Regular expressions were originally used to describe "regular sets," which were patterns under study by neurophysiologists.
Credit for the first regular expressions is given to the mathematician Stephen Kleene.
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NET there are controls that rely on the language of regular expressions.