Question

I want to read a file using shell script and here want to calculate the time required to read a file. I have created below method to get the time in milliseconds at the start and end of the file reading and I will calculate the time difference, but it is not adding the hour+minute+seconds and showing me that the required numeric input.

Method

  getCurrentTimeInMili()
   {
    hourTime=$(($(date +%H)*3600))
    minuteTime=$(($(date +%m)*60))
    secondTime=$(date +%S)
    timeInMili= $(($hourTime + $minuteTime + $secondTime));
    return timeInMili
   }

Error
./testshell.sh: line 17: return: timeInMili: numeric argument required

Answer 1

Invoking date multiple times means that their return values can be a bit out of sync with each other — which could be bad if we’re invoked just before a second boundary. Better is to call date only once and retrieve all the information desired, like so:

getCurrentTimeInMili() {
  date +'%H 3600 * %M 60 * + %S + 1000 * %N 1000000 / + p' | dc
}

startTime=$(getCurrentTimeInMili)
sleep 5
endTime=$(getCurrentTimeInMili)

If you don’t need this much accuracy, you can simply use the time builtin, as in:

time sleep 5