等待和睡眠之间的区别

Question

wait和 sleep？

Answer 1

wait等待一个过程完成；sleep睡一定次。

Answer 2

等待是一个bash内置命令。来自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.

睡眠不是内置命令。这是一个延迟指定时间的实用程序。

sleep命令可以支持以各种时间单位等待。GNU Coreutils 8.4 man sleep说：

    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.

Answer 3

sleep只是延迟了给定数量的秒数。

wait使外壳等待给定的作业。例如：

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

延迟外壳，直到两个子过程都完成