sleep

sleep does nothing for a given length of time, then exits.

sleep number[suffix]...

$ sleep 5          # pause for five seconds
$ sleep 1.5h       # pause for an hour and a half

It is used to space things out — a pause between the steps of a script, a delay before a retry.

Specifying the duration

number may be a whole number or a fraction. A suffix gives the unit:

Suffix	Unit
`s`	Seconds. This is the default if no suffix is given.
`m`	Minutes.
`h`	Hours.
`d`	Days.

Given more than one argument, sleep waits for the sum of them — sleep 1m 30s pauses for ninety seconds.

Code	Meaning
`0`	The full time elapsed.
`1`	A bad argument, or `sleep` was interrupted before the time was up.