grep

[Jon Kettenhofen]

Brian's is a better answer

On 08/24/2014 05:48 PM, Brian Cluff wrote:
> It tells grep to use the Extended regular expressions.  Further down in
> the man page for grep it defines the various regular expressions as:
>
> "grep understands three different versions of regular expression syntax:
> “basic” (BRE), “extended” (ERE) and “perl” (PRCE). In GNU grep, there is
> no difference in available functionality between
> basic and extended syntaxes. In other implementations, basic regular
> expressions are less powerful. The following description applies to
> extended regular expressions; differences for basic
> regular expressions are summarized afterwards. Perl regular expressions
> give additional functionality, and are documented in pcresyntax(3) and
> pcrepattern(3), but only work if pcre is available
> in the system."
>
> So the current versions of grep treat the basic and extended regular
> expressions as the same, so if they aren't powerful enough you will want
> to use the -P flag to get the PERL regular expressions.
>
> Here's a good web page that will show you the differences between basic
> and extended regular expressions:
> http://www.regular-expressions.info/posix.html
>
> Brian Cluff
>
> On 08/24/2014 02:21 PM, Michael Havens wrote:
>> what does the -E option do. The man page leaves much to be desired....
>> :-)~MIKE~(-:
>>
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