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Wow, this actually matched an é. What happened here? I would like it to not matching anything other than typically lower case letters.
$ echo "frappé"|egrep -E "^[a-z]+$" frappé egrep (GNU grep) 2.16 on Ubuntu 14.04
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A regular expression (shortened as regex or regexp; sometimes referred to as rational expression) is a sequence of characters that specifies a search pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation.
To match a character having special meaning in regex, you need to use a escape sequence prefix with a backslash ( \ ). E.g., \. matches "." ; regex \+ matches "+" ; and regex \( matches "(" . You also need to use regex \\ to match "\" (back-slash).
In C#, Regular Expression is a pattern which is used to parse and check whether the given input text is matching with the given pattern or not. In C#, Regular Expressions are generally termed as C# Regex. The . Net Framework provides a regular expression engine that allows the pattern matching.
[A-Za-z0-9_.]
Your locale setting tells egrep/grep -E how to collate the [a-z] character range.
$ export LC_COLLATE=C $ echo "frappé" | egrep '^[a-z]+$' # no match $ export LC_COLLATE=en_US.utf8 $ echo "frappé" | egrep '^[a-z]+$' frappé Named character classes can be used to match characters with diacritics in spite of the locale:
$ export LC_COLLATE=C $ echo "frappé" | egrep '^[[:lower:]]+$' frappé If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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