grep

[Brian Cluff]

Better to have too much info, too many replies, than not enough... 
Unless you bury an answer about grep in the middle of war and peace.

Brian Cluff

On 08/24/2014 02:53 PM, Jon Kettenhofen wrote:
> 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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