[opensuse] regexp -- defference between \< and \b ?
Listmates: With regular expressions, what is the difference between \< and \b ? The man page says: "The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word..." What is the difference between being at the "beginning or end" of a word or at the "edge" of a word? Presuming that "The (word) symbol \w is a synonym for [[:alnum:]]" The concept eludes me..... -- David C. Rankin, J.D., P.E. Rankin Law Firm, PLLC 510 Ochiltree Street Nacogdoches, Texas 75961 Telephone: (936) 715-9333 Facsimile: (936) 715-9339 www.rankinlawfirm.com -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
On Tuesday 29 April 2008 17:58, David C. Rankin wrote:
Listmates:
With regular expressions, what is the difference between \< and \b ? The man page says:
Which man page? There are many, many programs and libraries that implement regular-expression matching, and REs are by no means singly defined. There are many grammars for notating them and many varieties of fundamental matching constructs.
"The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word..."
What is the difference between being at the "beginning or end" of a word or at the "edge" of a word? Presuming that "The (word) symbol \w is a synonym for [[:alnum:]]"
Well, beginnings happen only at the beginning. Ends happen only at the end. Boundaries are either. (Am I going too fast for you??)
The concept eludes me.....
I wasn't aware of any RE system that implements both the "directional" word boundaries (\< and \>) and the neutral one (\b). Personally, I prefer the old-style \< and \> but apparently they're a thing of the past.
-- David C. Rankin
Randall Schulz Nobody -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
Randall R Schulz wrote:
On Tuesday 29 April 2008 17:58, David C. Rankin wrote:
Listmates:
With regular expressions, what is the difference between \< and \b ? The man page says:
Which man page? There are many, many programs and libraries that implement regular-expression matching, and REs are by no means singly defined. There are many grammars for notating them and many varieties of fundamental matching constructs.
Actually it comes from man grep. Specifically: The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The symbol \w is a synonym for [[:alnum:]] and \W is a synonym for [^[:alnum:]].
end. Boundaries are either. (Am I going too fast for you??)
Trying to digest BRE (basic RE), ERE (extended RE) and ARE (Advanced RE) in a couple of readings itself moves too fast for me ;-)
Personally, I prefer the old-style \< and \> but apparently they're a thing of the past.
Thanks for your help Randall! -- David C. Rankin, J.D., P.E. Rankin Law Firm, PLLC 510 Ochiltree Street Nacogdoches, Texas 75961 Telephone: (936) 715-9333 Facsimile: (936) 715-9339 www.rankinlawfirm.com -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
On Tuesday 29 April 2008 21:53, David C. Rankin wrote:
Randall R Schulz wrote:
On Tuesday 29 April 2008 17:58, David C. Rankin wrote:
Listmates:
With regular expressions, what is the difference between \< and \b ? The man page says:
Which man page? ...
Actually it comes from man grep. Specifically:
The Backslash Character and Special Expressions The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, ...
I guess it's been a long time since I've read the man page for the grep family. I didn't realize \b and \B were a part of Gnu grep.
end. Boundaries are either. (Am I going too fast for you??)
Trying to digest BRE (basic RE), ERE (extended RE) and ARE (Advanced RE) in a couple of readings itself moves too fast for me ;-)
Personally, I prefer the old-style \< and \> but apparently they're a thing of the past.
I know that the Java standard library RE patterns don't have \< and \>, and apart from egrep and sed, most of the time I enter a regular expression it's in a Java application (or code) that uses those library classes, so I have to use \b.
Thanks for your help Randall!
Sure. I learned something, too.
-- David C. Rankin
Randall Schulz -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org
participants (2)
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David C. Rankin
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Randall R Schulz