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

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

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. instead of
    $(date +%s)
    $(date +%s%N)

    and you will get nanoseconds precision

    Mitsuhashi Da! Oboeteoke!

  3. i need to find the no.of days between system date and the date of file creation. how do i achieve this?

  4. i need to find the no.of days and time between system date and the date of file creation. how do i achieve this?

    1. This will remove all files modified 30 or more days ago.

      for file in “$( /usr/bin/find /path/to/your/files -type f -mtime +30 )”
      /bin/rm -v -f $file

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

  6. 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

  7. 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.

  8. @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.

  9. 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

  10. I want to get system time alone. How do I get it from shell script? Anyone please suggest scripts

  11. write a script, ” How much time it will take to boot up the device”?, can anyone help me?

  12. 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 ;)

  13. 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
  14. 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

  15. 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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