Quick Script Question: Waiting for a (period)

[Charles Harris]

Dear all,

I need a method of setting a pause from within a script, other than sleep. I want to be able to wait for a random amount of time betweet 0 and 1 sec.

Does anyone have a reliable non hardware dependant solution ?

All tips, pointers, RTFF's , RTFM's warmly received as ever !!

Cheers,

-ChaZ-

[harry d brown jr]

You could use perl to randomly come up with a value between 0 and 1, then multiply that by some factor, say 100 (or maybe the mhz of the processor), then perform some large calculation in a loop.

live free or die
harry

[Robin Wakefield]

Hi Charles,

With perl:

perl -e "select(undef,undef,undef,\$ARGV[0]);" n

will work for fractional values of n.

Rgds, Robin.

[Alexander M. Ermes]

Hi there.
Look at script and check, whether you can use it :


today_=`date +'%y-%m-%d'`; export today_
#
LOG1=/usr/tmp/cpio_${today_}.1st; export LOG1
#
PATH=$PATH:/usr/local/bin
export PATH
exec > /usr/tmp/cpio_${today_}.log 2>&1
#
#
find / -depth -print | cpio -ocBv > /dev/rmt/0m 2>> ${LOG1} &
first_cpio=$!; export first_cpio
#
wait $first_cpio

if test $? -ne 0; then
echo "Full Offline Backup did not complete successfully!"
fi
echo "Time is: `/bin/date`"
echo "Time is: `/bin/date`"
echo "Time is: `/bin/date`" >> ${LOG1}


--------------------
Rgds
Alexander M. Ermes

[Robin Wakefield]

Hi Charles,

Might help if I read the question - this will give you a random sleep between 0 and 1 secs:

perl -e "srand;select(undef,undef,undef,rand);"

Rgds, Robin.

[Charles Harris]

Thanks for the tips everyone, I know Perl would be an obvious choice, but I'm stuck with the good old shell.

I really need something available from the shell even if it's not very accurate. I've tried loops etc, but I don't really want to write code that hammers the server into making a delay.

Any other thoughts ?


Thanks again!

-ChaZ-

[Krishna Prasad]

Why do you need to wait for 0 - 1 second? If 1 second is OK why not sleep 1?

I guess you could just ran a command that doesn't do anything except take up time.
something like

echo "do nothing" > /dev/null

[Charles Harris]

Belive it or not I want the delay to a realism to the following code. PLEASE NOTE it is not being used for deception, only to (nicely) illustrate the practical (or not very) use of arrays.

snip:

#!/usr/bin/sh
# scroll
# Don't ask.

typeset -i x=0
strg_len=$(echo "$*" | wc -m)
clear

while (( x < $strg_len )) && (( $strg_len < 1024 ))
do
(( x = x + 1 ))
scroll[x]=`echo "$*" |cut -c $x`
print "${scroll[x]}\c"
sleep 1
done
tput cud1

Cheers,


-ChaZ-

[A. Clay Stephenson]

Hi:

You have a fundamental problem in that sleep has second resolution. However, there is a system call, nanosleep, which has much finer resolution. You could write a very small C program which nanosleeps for an amount of time based upon the random parameter passed in by the calling process - your shell script. The entire C program would be at most 20 lines of code.

[Charles Harris]

Thanks again for the tips, by the look's of it I'm going to have to try my hand at C
Could someone point me in the right direction?

Cheers,


-ChaZ-

[Andreas Voss · Accepted solution]

Hi,

write this little c program:

main(argc, argv)
int argc;
char **argv;
{
usleep(atoi(argv[1]));
}

Compile ie:
cc usleep.c -o usleep

Run it ie:
usleep 100

will wait 10 micro seconds before continue.

Regards

[A. Clay Stephenson]

Hi Charles:

Here is my 2 minute C program. Use it like this: nanosleep 4500 to cause a 4500 msec delay or nanosleep 750 to cause a 750msec delay.


Regards, Clay

[Robin Wakefield]

Hi Charles,

Here's one that gives you random tenths of a second delays:

#include
#include

int main()
{
int m;
srand((unsigned long)time(NULL));
m = 100000*(int) (10.0*rand()/(RAND_MAX+1.0));
/* printf("%d\n",m); */
usleep(m);

return 0;
}


Rgds, Robin.

[Charles Harris]

Thanks to everyone who helped out with this, the C code has been particularly useful !

I'll get compiling later today and make sure everything's okay.


Cheers!

-ChaZ-