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How to rewrite the [a-zA-Z0-9!$* \t\r\n] pattern to match hyphen along with the existing characters ?
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Most characters, including all letters ( a-z and A-Z ) and digits ( 0-9 ), match itself. For example, the regex x matches substring "x" ; z matches "z" ; and 9 matches "9" . Non-alphanumeric characters without special meaning in regex also matches itself. For example, = matches "=" ; @ matches "@" .
You only need to escape the dash character if it could otherwise be interpreted as a range indicator (which can be the case inside a character class).
If you add a * after it – /^[^abc]*/ – the regular expression will continue to add each subsequent character to the result, until it meets either an a , or b , or c . For example, with the source string "qwerty qwerty whatever abc hello" , the expression will match up to "qwerty qwerty wh" .
A regular expression to match everything before a specific character makes use of a wildcard character and a capture group to store the matched value. Another method involves using a negated character class combined with an anchor.
The hyphen is usually a normal character in regular expressions. Only if it’s in a character class and between two other characters does it take a special meaning.
Thus:
[-] matches a hyphen.[abc-] matches a, b, c or a hyphen.[-abc] matches a, b, c or a hyphen.[ab-d] matches a, b, c or d (only here the hyphen denotes a character range).
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