There also is a \w regexp operator in perl regexp and in PCRE.
However, it currently has a bug in that it only matches single-byte characters (for instance, not é in a UTF-8 locale even though that's clearly a letter and even though it does match é in all the locales where é is a single character). It's meant to match alnums and underscore in your locale. GNU grep used to have its own regexp engine however it now uses the GNU libc's one (though it does embed its own copy). The behaviour for \w alone is not specified by POSIX, so implementations are allowed to do what they want.
So you won't find a grep or sed implementation where that's available (unless via non-standard options). is required by POSIX to match either backslash or w. That matches letters and digits in your locale (note that often includes a lot more than a-zA-Z0-9 unless the locale is C). In POSIX BRE and ERE, you have the character class. Standards exist so that one can rely on a minimum set of features that are available across all conforming applications.įor instance, all modern implementations of sed and grep implement basic regular expressions as specified by POSIX (at least one version or the other of the standard, but that standard has not evolved a lot in that regard in the last few decades). The documentation of each will tell you what they support. Different tools and versions thereof support different variants of regular expressions.
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