Recipe: Calculating execution time for a command

$ time COMMAND

$ time ls
test.txt
next.txt
real	0m0.008s
user	0m0.001s
sys	0m0.003s

$ time -o output.txt COMMAND

$ time -a output.txt COMMAND


Formatted output:
$ time -f “Time: %U” -a output.txt COMMAND
#“Time: %U” is the format string