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#!/bin/bash
# this function is used to sleep a fraction of a second
# it calculates the difference between every time is called
# and tries to align the sleep time to give you exactly the
# loop you need.
LOOPSLEEP_DATE="$(which date)"
if [ -z "$LOOPSLEEP_DATE" ]
then
echo >&2 "$0: ERROR: Cannot find the command 'date' in the system path."
exit 1
fi
LOOPSLEEPMS_LASTRUN=0
LOOPSLEEPMS_LASTSLEEP=0
LOOPSLEEPMS_LASTWORK=0
LOOPSLEEPMS_HIGHRES=1
test "$($LOOPSLEEP_DATE +%N)" = "%N" && LOOPSLEEPMS_HIGHRES=0
now_ms=
current_time_ms() {
# if high resolution is not supported
# just sleep the time requested, in seconds
if [ $LOOPSLEEPMS_HIGHRES -eq 0 ]
then
now_ms="$($LOOPSLEEP_DATE +'%s')000"
else
now_ms="$(( $( $LOOPSLEEP_DATE +'%s * 1000 + %-N / 1000000' ) ))"
fi
}
loopsleepms() {
local tellwork=0 t="$1" div s m now mstosleep
if [ "$t" = "tellwork" ]
then
tellwork=1
shift
t="$1"
fi
div="${2-100}"
# $t = the time in seconds to wait
# if high resolution is not supported
# just sleep the time requested, in seconds
if [ $LOOPSLEEPMS_HIGHRES -eq 0 ]
then
sleep $t
return
fi
# get the current time, in ms
# milliseconds since epoch (1-1-1970)
now="$(( $( $LOOPSLEEP_DATE +'%s * 1000 + %-N / 1000000' ) ))"
# calculate required sleep in ms
t=$((t * 1000 * div / 100))
# this is our first run
# just wait the requested time
test $LOOPSLEEPMS_LASTRUN -eq 0 && LOOPSLEEPMS_LASTRUN=$now
# calculate ms since last run
LOOPSLEEPMS_LASTWORK=$((now - LOOPSLEEPMS_LASTRUN - LOOPSLEEPMS_LASTSLEEP))
# echo "# last loop's work took $LOOPSLEEPMS_LASTWORK ms"
# calculate ms to sleep
mstosleep=$(( t - LOOPSLEEPMS_LASTWORK ))
# echo "# mstosleep is $mstosleep ms"
# if we are too slow, sleep some time
test $mstosleep -lt 200 && mstosleep=200
s=$((mstosleep / 1000))
m=$((mstosleep - (s * 1000)))
test $tellwork -eq 1 && echo >&2 " >>> PERFORMANCE >>> WORK TOOK $LOOPSLEEPMS_LASTWORK ms ( $((LOOPSLEEPMS_LASTWORK * 100 / 1000)).$((LOOPSLEEPMS_LASTWORK % 10))% cpu ) >>> SLEEPING $mstosleep ms"
# echo "# sleeping $s.$m"
# echo
sleep $s.$m
# keep the values we need
# for our next run
LOOPSLEEPMS_LASTRUN=$now
LOOPSLEEPMS_LASTSLEEP=$mstosleep
}
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