How to do simple date (time) calculation in shell script?

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# 1  
Old 09-16-2013
How to do simple date (time) calculation in shell script?


I'm looking for a way to do a simple math calc during a shell script as a means of logging how long a particular task takes.

For example...
STARTTIME=whenever this script starts
./path/to/ >>logfile.log
TOTALTIME=<time at this stage of the script after above command finished> - $STARTTIME
ECHO This command took $TOTALTIME to complete. >>logfile.log

I know that's a crude representation, but hopefully enough to communicate what I'm looking to accomplish.

Thank you!!
# 2  
Old 09-16-2013
Most shells have a SECONDS special variable you can use.

echo "Seconds since start of script:  $SECONDS"
sleep 10
echo "Seconds since start of script:  $SECONDS"

# 3  
Old 09-16-2013
Wow. That's super easy. Is there away to format that number to minutes? A simple divide by 60 is all I need...
# 4  
Old 09-16-2013
Depends on your shell, in BASH or KSH it's not hard:

printf "%02dH %02dM %02dS\n" $(( SECONDS/(60*60) )) $(( SECONDS/60 ))  $(( SECONDS%60 ))

# 5  
Old 09-16-2013
And yet I couldn't find that by doing web searches. I do try before I post. Thank you SO much!

I tried to make that a variable in order to insert it into a sentence, and it didn't work.


sleep 10

SCRIPTTIME= printf "%02dH %02dM %02dS\n" $(( SECONDS/(60*60) )) $(( SECONDS/60 ))  $(( SECONDS%60 ))

echo "This script took $SCRIPTTIME to run."

The output was:
00H 00M 10S
This script took  to run.

# 6  
Old 09-16-2013
Variables don't work that way. You'd want to put it in `backticks` to put in in a variable.

Also, you don't want spaces after the equals sign. VARIABLE=something is good, VARIABLE=" something" is good, VARIABLE= something does something very different -- it blanks VARIABLE before attempting to run the program something...

But why not just jam it right into the printf statement, get it all done in one go?

printf "This script took %02dH %02dM %02dS to run\n" \
        $(( SECONDS/(60*60) )) $(( SECONDS/60 ))  $(( SECONDS%60 ))

The \ on the end of the line lets you continue it on the next line, instead of making one super-long line...
# 7  
Old 09-16-2013
Using your logic.

STARTTIME=`date +"%s"`
./path/to/ >>logfile.log
TOTALTIME=$(expr `date +"%s"`  - $STARTTIME)
ECHO This command took $TOTALTIME to complete. >>logfile.log

Last edited by Aia; 09-16-2013 at 07:44 PM.. Reason: Syntax error.
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