stopwatch - measures time between a certain start & end point

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# stopwatch v1.5 - simple tool to measure time between a certain start & end point                                         #
# Handshake:                                                                                                               #
# $SW_PREC sets the precision level. Higher values result in larger, more precise measurements (default: 3)                #
# Usage:                                                                                                                   #
# Simply call SW_TRIGGER() to start measuring. If called the first time, it sets the current time as start time. When      #
# called every other time, it calculates and shows the difference between start and current time and also sets the current #
# time as new start time. Note that the function itself takes about 10-30ms of processing time. Prints results to stdout.  #
############################################################################################################################

SW_START=

SW_TRIGGER(){
    [ -z "${SW_PREC##*[!0-9]*}" ] || [ $SW_PREC -lt 3 ] && SW_PREC=3
    SW_MULT=1$(printf %"$SW_PREC"s | tr " " "0")
    SW_TIME=$(date +%s:%"$SW_PREC"N | awk -F ':' '{print ($1*'$SW_MULT')+$2}')
    if [ -n "$SW_START" ]; then
        SW_DIFF=$(($(date +%s:%"$SW_PREC"N | awk -F ':' '{print ($1*'$SW_MULT')+$2}')-$SW_START))
        [ $SW_PREC -gt 3 ] && SW_DIFF=$(printf $SW_DIFF | awk '{printf("%."SW_DP"f\n",$1/10^SW_DP)}' SW_DP=$(($SW_PREC-3)))
        echo $SW_DIFF"ms"
    fi
    SW_START=$SW_TIME
}