+ sleep is used to pause for a specified number of seconds.
+ It comes in 3 versions:
+ - small: takes one integer parameter
+ - fancy: takes multiple integer arguments with suffixes:
+ sleep 1d 2h 3m 15s
+ - fancy with fractional numbers:
+ sleep 2.3s 4.5h sleeps for 16202.3 seconds
+ Last one is "the most compatible" with coreutils sleep,
+ but it adds around 1k of code.