elapsed time for each rule

Question

I have this bash code:

(At the start of the script:)

function timer()
{
    if [[ $# -eq 0 ]]; then
        echo $(date '+%s')
    else
        local  stime=$1
        etime=$(date '+%s')

        if [[ -z "$stime" ]]; then stime=$etime; fi

        dt=$((etime - stime))
        ds=$((dt % 60))
        dm=$(((dt / 60) % 60))
        dh=$((dt / 3600))
        printf '%d:%02d:%02d' $dh $dm $ds
    fi
}

t=$(timer)

(and, at the end of the script:)

printf 'Elapsed time: %s\n' $(timer $t)

to calculate the total time elapsed by the script. This code works fine in a bash (shell) script. So, I want to put this code in a makefile for each rule.

How can I put this function in Makefile? And how can call'em in each rule?

I made something like this:

define TIME
     stime=$(1)
     etime=$(date '+%s')
     dt=$((etime - stime)) \
     ds=$((dt % 60)) \
     ...
endef

and in each rule:

rule1: dep1 dep2 dep3
    ...SOME STUFF
    @$(call TIME, starttime)

rule2: depx depD rule1
    ...SOME STUFF
    @$(call TIME, starttime)

but the math operation does not work. I tried a lot of things but I can't do works

Answer 1

The trouble is that in your bash script, the variable t survives from the beginning (before the work) to the end (when it can be subtracted from the end time). In a Make recipe, each line has its own shell, so a shell variable set in an early line won't be available in a later line.

You could string all of the commands of a recipe together in one line, so that you can set t at the beginning and use it at the end, but that's pretty clumsy. I'd suggest you write t to a file, maybe rule1_time, so that the two calls to timer don't require a common variable. Oh, and don't try to use call inside a command:

STIME = date '+%s' > $@_time
ETIME = read st < $@_time ; echo $$((`date '+%s'`-$$st))

all:
    $(STIME)
    do stuff
    $(ETIME)

EDIT:
I wrote the code above as a proof of concept; I was going for clarity, not refinement. If I understand your comment correctly, you now want to know how to break down the time into hours, minutes and seconds, without calling several functions from each rule. There are several ways to do it, this is probably the cleanest:

ETIME = @read st < $@_time ; st=$$((`date '+%s'`-$$st-68400)) ; echo Elapsed time: `date -d @$$st '+%H:%M:%S'`