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Regex - Return numbers of exactly 8 digits

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Top Forums Shell Programming and Scripting Regex - Return numbers of exactly 8 digits
# 15  
Old 08-22-2012
Have you tried:

Code:
grep -o '[0-9]\{8\}' input.txt

-Rob.
# 16  
Old 08-22-2012
Quote:
Originally Posted by Rob Butler
Code:
grep -o '[0-9]\{8\}' input.txt

In addition to matching an 8-digit number, that will also extract 8 digits from longer numbers. That may or may not be desired.

Regards,
Alister
# 17  
Old 08-22-2012
All of the above solution looks perfectly good, i really don't know whats going on in your system.
You may try like this also:
Code:
grep -Ew '\"[0-9]{8}\"'  <file>| sed 's/''//g'

# 18  
Old 08-22-2012
Quote:
Originally Posted by InduInduIndu
All of the above solution looks perfectly good, i really don't know whats going on in your system.
The user mentioned that his system runs Linux. There's a good chance that its awk is gawk. Until the release of 4.0.0 (about a year ago), gawk's default regular expression syntax did not support intervals. Expressions such as [0-9]{8} would not work as intended (according to POSIX extended regular expression syntax) without the --posix or --re-interval command line option.

Regards,
Alister
Last edited by alister; 08-22-2012 at 02:12 PM..
# 19  
Old 08-22-2012
Regex - Return numbers of exactly 8 digits
You are right!

However, i dont understand why people go for awk, nawk, when simple things like grep works.

I simply follow this:
1. Can it be done by Basic Regex? => yes, go for grep & sed
2. No, and still can it be done by grep's -P & -E options? Yes then go for that.
3. Then i go for Awk & perl.

Yes, always condition applies. If something data/table/fileds awk is amazing.If somethings kind of subtitution then sed,perl are awesome.
# 20  
Old 08-22-2012
Quote:
Originally Posted by InduInduIndu
However, i dont understand why people go for awk, nawk, when simple things like grep works.

... <snip> ...

2. No, and still can it be done by grep's -P & -E options? Yes then go for that.
Not everyone is using GNU grep. That -P option is not implemented my most greps. I had never even heard of it until you mentioned it. Looking at the documentation, it doesn't sound like it's production ready even if portability is not a concern.

Quote:
-P
--perl-regexp
Interpret the pattern as a Perl regular expression. This is highly experimental and ‘grep -P' may warn of unimplemented features.
grep Programs - GNU Grep 2.14

Regards,
Alister
# 21  
Old 08-22-2012
Quote:
Originally Posted by itkamaraj
may be because of the awk version.

what is your awk version ?

Code:
 
awk --version

Hi itkamaraj,

GNU Awk 3.1.5

is this a problem as said in recent posts...?
Last edited by pamu; 08-23-2012 at 04:12 AM..
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