Regex in R: matching the string before a sequence of characters

Question

I want to extract a part of the string that comes before a certain word. E.g. I want to get everything before \", useless\".

a <- \"Experiment A, useless (03/         


        

Answer 1

We can use sub to match the , followed by zero or more spaces (\\s*) followed by 'useless' and other characters that follow (.*) and replace it with blank ("")

sub(",\\s*useless\\b.*", "", a)
#[1] "Experiment A"