[SATLUG] character classes with *

mike perez meekprize at gmail.com
Wed Oct 1 15:51:57 CDT 2014


the contents of his file is "aaLLyLayLaaya*?"

On Wed, Oct 1, 2014 at 3:46 PM, Bruce Dubbs <bruce.dubbs at gmail.com> wrote:

> MaxPower wrote:
>
>> I'm having a bit of a hard time wrapping my head around what is
>> actually going on here.  I'm attempting to learn about regular
>> expressions and this use of character classes with * has me
>> befuddled.
>>
>
> lap007:~/crap$ cat testaaLLyLayLaaya*
>
> So what is the content of the file(s) named testaaLLyLayLaaya*?
>
> lap007:~/crap$ grep [abcdez]* test
> ##why does this command include everything in the file
> (even the upper case L)?aaLLyLayLaaya*
>
>
> lap007:~/crap$ grep [a-z]* test
> ##while this command excludes everything in the file?
>
> lap007:~/crap$
> lap007:~/crap$ grep [abcde]* test
> ## once again total file returned aaLLyLayLaaya*
>
>
> lap007:~/crap$ grep [abcdef]* test
> ##the addition of the letter f returns a null set? buh?
>
>
>  I understand that * isn't being used in its normal way and while I
>> grasp the logic behindgrep [a-z].* test, grep [a-z]\* test, and grep
>> '[a-z]*' the above has me quite miffed.
>>
>
> First of all, the shell may be interpreting characters like [, ], and *.
> Eliminate that by enclosing in single quotes:
>
> grep '[abcdez]*' test
>
> Secondly, the above is asking to match zero or more of the characters a,
> b, c, d, e, or z.  That probably matches anything but I really don't know
> the contents of the file you are asking about.
>
>   -- Bruce
>
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-- 
-m.a.perez
KF5QVO


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