Shell script to get the time difference

Posted on in Categories , , , , last updated September 19, 2007

Q. I am able to write PHP or Perl script where I can find out time difference between script executions. Now I have .shtml file that is nothing but a shell script outputting some data to browser. What I want is time difference or time it took to execute a script. How do I write a shell script?

A. Your Logic should be as follows:

* Get start time and store to a variable START

* Execute a shell script

* Grab output and send to web browser

* Get time again and store to a variable END

* Calculate difference using expression END – START

Shell script o get the time difference

Here is small script that does the same thing (please note that script teated on GNU/Linux and with GNU date command only):
$ vi timediff.bash
Append text as follows:

START=$(date +%s)
# do something

# start your script work here
ls -R /etc > /tmp/x
rm -f /tmp/x
# your logic ends here

END=$(date +%s)
DIFF=$(( $END - $START ))
echo "It took $DIFF seconds"

Save and execute the script as follows:
$ chmod +x timediff.bash
Execute the script:
$ ./timediff.bash

It took 4 seconds

33 comment

  1. What ifmy script takes mili seconds to execute and I want to be able to measure the time difference even if it is few micro seconds or mili seconds.



  2. The above mentioned script will not work because “%s” is given in small letter.
    Replace “%s” with “%S” and the script will work.

  3. How do i find time difference between two file .
    Example: One file created at Wed Feb 18 10:08:34 IST 2009.And Anothe file created at
    Wed Feb 18 23:32:36 IST 2009. How do i find difference between Wed Feb 18 23:32:36 IST 2009 – Wed Feb 18 10:08:34 IST 2009 ?
    Please Help

  4. Just a comment:
    %s does not work on Solaris. %S does, but it only returns the seconds part of the date-time, not the number of seconds since 00:00:00, Jan 1, 1970 so you would have to deal with the math of changes in minutes, hours and the turn over from 59 to 0.

  5. @Achala
    difference between 2 files in seconds:
    use date -r for the modification date of the file and +%s for date in seconds:
    Example 2 files bobo.png and foobar.ppm
    echo `date -r bobo.png +%s`-`date -r foobar.ppm +%s` | bc
    echo “8411376/(24*3600)”|bc -l
    So 97 days between these files.

  6. Stumbled upon this example. The script in article is all very fine as a script exercise, but it does not follow bash logic. If you want to get the running time of – lets say – a_long_process
    you just execute:
    time a_long_process
    simple, isn’t it? For more options check: man time

  7. by the way that will be in shell… as most of your answers and since i googled for bash and this came so i thought might be usefull for people who come via google to this page by mistake ;)

  8. If you want to have the time difference based on entries in a logfile, you first have to convert the found dates to seconds.

    >  date -s 'Dec 17 14:38:01'
    Tue Dec 17 14:38:01 CET 2013
    >  date -s 'Dec 17 14:38:01' +%s
  9. Do you know about the ‘time’ command.

    Simply put ‘time’ before whatever script you want to run, and afterwards you will get stats how much time it took.

    For exemple:

    time sleep 5

    real 0m5.001s
    user 0m0.000s
    sys 0m0.000s

  10. Hello,

    In my ksh file the below two lines of code written for start/end time of some process.
    echo launch TIMESTAMP START: $(date +”%Y.%m.%d %H:%M:%S”)
    echo launch TIMESTAMP END: $(date +”%Y.%m.%d %H:%M:%S”)

    which showing ouput as:
    showing in log as : launch TIMESTAMP START: 2016.05.24 06:30:35
    showing in log as : launch TIMESTAMP END: 2016.05.24 14:55:05

    Now please let us know how i take total time taken for this process. just to inform you that (END-START will not help in this and showing incorrect output while considering all difficult combinations)

    Please help!
    Thanks in Advance.

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