Run a list of commands (one per line) with a certain concurrency.

parallelize.sh

cat big_list_of_commands.txt | tr '\n' '\0' | xargs -0 -n1 -P{thread-count} bash -c

# or, per the example given:

(for i in 1 2 3 4 5 6 7 8 9 10; do echo "echo 'Delay $i'; sleep $i ; echo 'Done $i'" ; done) | tr '\n' '\0' | xargs -0 -n1 -P4 bash -c