Ruby removes everything but some characters?
How to remove all characters from a string except spaces, numbers, and some others? Something like that:
oneLine.gsub(/[^ULDR0-9\<\>\s]/i,'')
I just need to: 0-9 l d u r < > <space>
Also, is there a good document on using regex in Ruby, like a list of special characters with examples?
The regex is already working correctly. However, you need to revert the result to the line you are working on. Otherwise, you are not changing the line ( .gsub()
not changing the line in place).
You can improve the regex a bit by adding the '+' quantum (so that consecutive characters can be replaced in one go). Also, you don't need to hide the angle brackets:
oneLine = oneLine.gsub(/[^ULDR0-9<>\s]+/i, '')
A good resource with a special focus on Ruby regular expressions is the Regular Expressions Cookbook by Jan Goywaerts and Stephen Levitan. A good online tutorial by the same author is here .
The good old school String#delete
does it without regex. ^
means "NOT".
str = "12eldabc8urp pp"
p str.delete('^0-9ldur<> ') #=> "12ld8ur "
Just for completeness: you don't need a regex for this particular task, it can be done with simple string manipulation :
irb(main):005:0> "asdasd123".tr('^ULDRuldr0-9<>\t\r\n ', '')
=> "dd123"
There is also a method tr!
if you want to replace the old value:
irb(main):009:0> oneLine = 'UasdL asd 123'
irb(main):010:0> oneLine.tr!('^ULDRuldr0-9<>\t\r\n ', '')
irb(main):011:0> oneLine
=> "UdL d 123"
It should also be slightly faster (but performance shouldn't be a big issue in Ruby :)