Difference between wait and sleep

339
votes

What is difference between wait and sleep?

3
bashshellwaitsleep

3 Answers

399
votes

wait waits for a process to finish; sleep sleeps for a certain amount of seconds.

128
votes

wait is a BASH built-in command. From man bash:

    wait [n ...]
        Wait  for each specified process and return its termination sta-
        tus.  Each n may be a process ID or a job  specification;  if  a
        job  spec  is  given,  all  processes in that job's pipeline are
        waited for.  If n is not given, all currently active child  pro-
        cesses  are  waited  for,  and  the return status is zero.  If n
        specifies a non-existent process or job, the  return  status  is
        127.   Otherwise,  the  return  status is the exit status of the
        last process or job waited for.

sleep is not a shell built-in command. It is a utility that delays for a specified amount of time.

The sleep command may support waiting in various units of time. GNU coreutils 8.4 man sleep says:

    SYNOPSIS
        sleep NUMBER[SUFFIX]...

    DESCRIPTION
        Pause for NUMBER seconds.  SUFFIX may be ‘s’ for seconds (the default),
        ‘m’ for minutes, ‘h’ for hours or ‘d’ for days.  Unlike most  implemen-
        tations  that require NUMBER be an integer, here NUMBER may be an arbi-
        trary floating point number.  Given two or more  arguments,  pause  for
        the amount of time specified by the sum of their values.
96
votes

sleep just delays the shell for the given amount of seconds.

wait makes the shell wait for the given job. e.g.:

workhard &
[1] 27408
workharder &
[2] 27409
wait %1 %2

delays the shell until both of the subprocesses have finished