using * as a wildcard 1

[noiz]

hi

I'm using the bourne shell in BSD 4.2 and i'm getting wierd results when i use a wildcard in a simple awk script i'm running.

when i run:
awk '/d*/ {print $0 }' tmp2 it matches every line i have in that file even those that don't start with "d"

when i run: awk '/dr*/ { print $0 }' tmp2 i get
drwxr-xr-x 3 zion users 512 May 21 02:34 .
drwxr-xr-x 3 zion users 512 May 1 11:09 ..
drwxr-xr-x 2 zion users 512 May 18 14:08 t1
-rw-r--r-- 1 zion users 273 May 18 18:17 tweedle
-rw-r--r-- 1 zion users 49 Mar 28 22:49 wordlist

but when i run:
awk '/drw*/ { print $0 }' tmp2 i get a list of only directories? any one know why it is doing this?

tks

zion
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[Krunek]

Hi, zion!

A bit of theory: asterisk * matches any number (or none) of the single character that immediately precedes it. So, /d*/ matches all lines in tmp2, because letter d is in any line.

You can get a list of only directories with this regular expression: /^d.*/. That means:
every line that has letter d at the beginning of the line. Metacharacter ^ matches the following regular expression at the beginning of the line.

God bless you!

KP.


God

 

[Krunek]

Hello, zion!

I found good site about regular expressions:

http://www.devshed.com/Server_Side/Administration/RegExp/

Excellent book for regular expressions is &quot;Mastering Regular Expressions,&quot; by Jeffrey E. F. Friedl; you can see this site:

http://www.oreilly.com/catalog/regex/

There is 4th chapter from Mr. Friedl's book on this site:

http://www.oreilly.com/catalog/regex/chapter/ch04.html

You can also try &quot;Regular-expression inspector:&quot;

http://www.builder.com/Programming/Kahn/050698/toolrei.html

Here you can find quick metacharacter reference.

RegExp is very powerful tool. I use it with awk for searching the Bible in ASCII format and for data analysis.

Bye!

KP.

 

[noiz]

Krunek,

Thanks, i'll check out those sites.

God bless,

zion
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