How do I remove a substring after a certain character in a string using Ruby?

I find that "Part1?Part2".split('?')[0] is easier to read.

new_str = str.slice(0..(str.index('blah')))

I'm surprised nobody suggested to use 'gsub'

irb> "truncate".gsub(/a.*/, 'a')
=> "trunca"

The bang version of gsub can be used to modify the string.