August 2012
Intermediate to advanced
609 pages
19h 16m
English
Content preview from Regular Expressions Cookbook, 2nd Edition
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
6.4. Octal Numbers
Problem
You want to find octal numbers in a larger body of text,
or check whether a string variable holds an octal number. An octal
number is a number that consists of the digits 0 to 7. The number must
either have at least one leading zero, or it must be prefixed with
0o.
Solution
Find an octal number in a larger body of text:
\b0[0-7]*\b
| Regex options: None |
| Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
Check whether a text string holds just an octal number:
\A0[0-7]*\Z
| Regex options: None |
| Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby |
^0[0-7]*$
| Regex options: None |
| Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python |
Find an octal number with a 0o prefix:
\b0o[0-7]+\b
| Regex options: Case insensitive |
| Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
Discussion
These regexes are very similar to the ones in the preceding recipes in this chapter. The only significant difference is that the prefix 0 is also part of the octal number itself. In particular, the digit 0 all by itself is also a valid octal number. So while the solutions for preceding recipes use the plus to repeat the digit ranges one or more times, the first two solutions in this recipe use the asterisk to repeat the digit ranges zero or more times. This way we allow octal numbers of any length, including the number 0.
The third solution uses the plus again, because we require at
least one digit after the 0o
prefix.
See Also
All the other recipes in this chapter show more ways of matching ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.