README.md

README

Demonstrate how to time operations in the shell to help with optimisation.

Reasons

Always a good idea to understand about the performance of scripts. Understanding if it meets expectations.

Example usage can be found here

TODO:

• hyperfine - https://github.com/sharkdp/hyperfine
• https://cr.yp.to/libtai/tai64.html
• https://www.reddit.com/r/commandline/comments/yle738/peculiar_shell_performance_differences_in/iuywce7

Use EPOCHREALTIME

Simple example of measuring sleep 10 command

# microsecond 1 millionth of second
start=${EPOCHREALTIME}
sleep 10
end=${EPOCHREALTIME}
runtime=$(bc <<< "(${end} - ${start})")
echo "${runtime} seconds"

Use time

Simple example of measuring sleep 10 command

time sleep 10     

Time it over iterations

# add a custom function to time 
function under_test() {
    echo "Parameters $*"
    local sleeptime=1
    if [[ -n $1 ]]; then
        sleeptime=$1
    fi
    echo "sleep $sleeptime"
    sleep $sleeptime
}

# pass function to test, number of iterations and parameters to pass into the function (sleeptime of 2 in this case)
. ./time-it.sh under_test 10 2