How do I do a short delay (milliseconds) in a shell script?

Shell Programming and Scripting
1

I need to put a small delay into a shell script. I'm looking for something smaller than "sleep" - a second is way too long. I want to sleep something like 10 milliseconds. I've tried "usleep" and "nanosleep", but the script doesn't recognize them.

I'm using the bash shell but I'm willing to switch to a different shell if it helps to find a command that will do the delay.

2

Will this work for you:

typeset -i mCnt=0
while [[ ${mCnt} -le 1000 ]]; do
  mCnt=${mCnt}+1
done

You can change the number according to your CPU speed.

3

GNU sleep can take a number like

sleep 0.1

to sleep a fraction of a second. And since you have BASH, you're probably on a GNU/Linux system.

This has nothing to do with what shell you use, since sleep is an external utility.

4

it will slowing down for few millisecond.

sleep 0

in perl try

perl -e 'select(undef,undef,undef,.1)'
5

I tried the "sleep 0.1" suggestion, but it says "sleep: bad character in argument".

It seems like the other suggestions are "doing it the hard way" in terms of forcing the script to do a lot of other processing to in effect slow it down. But if there's no better way to do a small delay then I'll have to resort to that.

6

Is it possible that you have 2 different sleeps-- a builtin and a binary? Perhaps see if /bin/sleep (or some other appropriate location...) can be called directly.

7

Actually, ksh has a built-in sleep which accepts a fractional argument. If the OP has ksh on his system, it may be an expedient solution.

Regards,
Alister

8

I've never heard about builtin sleep. It's just not GNU sleep (BSD on Mac, or something else). The variant with perl is the best solution (on modern enough boxes).

9

ksh93 does indeed have a built-in sleep.

GNU sleep is not special in this regard. I regularly use *BSD and every BSD's sleep(1) supports fractions of a second.

Regards,
Alister

1 Like
10

Oh, yes. I checked it in ksh with "which" but I should do it with "type". Too many shells, too many *nixes, too little experience... )))