[adolph]

Isn't the difference between a pipeline and a method chain that a pipeline doesn't have to wait for the previous process to complete in order to send results to the next step? Grep sends lines as it finds them to sed and sed on to xargs, which acts as a sink to collect the data (an is necessary otherwise wc -l would write out a series of ones).

Given File.readlines("haystack.txt"), the entire file must be resident in memory before .grep(/needle/) is performed, which may cause unnecessary utilization. Iirc, in frameworks like Polars, the collect() chain ending method tells the compiler that the previous methods will be performed as a stream and thus not require pulling the entirety into memory in order to perform an operation on a subset of the corpus.