How to delete specific characters from a string in Ruby?

If you just want to remove the first two characters and the last two, then you can use negative indexes on the string:

s = "((String1))"
s = s[2...-2]
p s # => "String1"

If you want to remove all parentheses from the string you can use the delete method on the string class:

s = "((String1))"
s.delete! '()'
p s #  => "String1"

For those coming across this and looking for performance, it looks like #delete and #tr are about the same in speed and 2-4x faster than gsub.

text = "Here is a string with / some forwa/rd slashes"
tr = Benchmark.measure { 10000.times { text.tr('/', '') } }
# tr.total => 0.01
delete = Benchmark.measure { 10000.times { text.delete('/') } }
# delete.total => 0.01
gsub = Benchmark.measure { 10000.times { text.gsub('/', '') } }
# gsub.total => 0.02 - 0.04

Using String#gsub with regular expression:

"((String1))".gsub(/^\(+|\)+$/, '')
# => "String1"
"(((((( parentheses )))".gsub(/^\(+|\)+$/, '')
# => " parentheses "

This will remove surrounding parentheses only.

"(((((( This (is) string )))".gsub(/^\(+|\)+$/, '')
# => " This (is) string "

Do as below using String#tr :

 "((String1))".tr('()', '')
 # => "String1"