Regular Expression to Match String Exactly?
I'll Preface This Question by Mentioning That While I'm Far from a Regular Expressions Guru, They Are Not Completely Foreign to Me. Building a Regular...
I'll preface this question by mentioning that while I'm far from a regular expressions guru, they are not completely foreign to me. Building a regular expression to search for a pattern inside a particular string generally isn't a problem for me, but I have a (maybe?) unique situation.
I have a set of values, say:
028938
DEF567987
390987.456
GHI345928.039
I want to match a certain set of strings, such as:
- Strings composed of exactly 6 digits
- Strings composed of exactly 6 digits, a decimal, followed by exactly 3 more digits
In the above examples, the first and third values should be matched.
I'm using the regular expressions:
[0-9]{6}
[0-9]{6}.[0-9]{3}
Unfortunately, since all the above examples contain the specified pattern, all values are matched. This is not my intention.
So my question, in a nutshell, is how to write a regular expression that matches a string exactly and completely, with no additional characters to the right or left of the matched pattern? Is there a term for this type of matching? (Google was no help.) TIA
5 Answers
use ^ and $ to match the start and end of your string
^[0-9]{6}$
^[0-9]{6}\.[0-9]{3}$
Reference:
Also, as noted by Mikael Svenson, you can use the word boundary \b if you are searching for this pattern in a larger chunk of text.
Reference:
You could also write both those regexes in one shot
^\d{6}(\.\d{3})?$
You can use ^ to require the matching at the start of a line and $ to require the end of a line
^[0-9]{6}\.[0-9]{3}$
[0-9] can also be written as \d
^\d{6}\.\d{3}$
You can also use \b for word boundaries if you want to match your pattern in a line with eg. spaces in them
\btest\b
will match the word test in this line
this is a test for matching
^\d{6}$
^\d{6}\.\d{3}$
are the correct patterns you can test them 6 digits only and 6 digits dot 3 digits.
^\d{6}((\.\d{3}$)|$)
will match either 6 digits or 6 digits dot 3 digits
Rubular is your friend!
Match this regex:
"^\d{6}((\.\d{3}$)|$)"
i think you want something like this:
"^\d{6}(\.\d{3})?$"
you need to escape the "dot" as it is "any" character in regexp.
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