How can I time portions of a Linux shell script?

Hi there.

Alternatively, most shells have a 'time' facility built-in. This works in bash; your milage may vary for other shells.

----------------------------------
#!/usr/bin/bash

{ time {
  # Your section 1 code goes here
} } 2> timing_section_1.txt

{ time {
  # Your section 2 code goes here
} } 2> timing_section_2.txt
----------------------------------

This will output real, user and cpu timing information into the text files specified.

(The slightly odd-looking code blocks are needed to appropriately redirect standard error to a file. See http://www.cs.tut.fi/~jarvi/tips/bash.html for an explanation.)

Hope this helps.

Regards,
NeilS.

thanks a lot!! i just grabbed your code, plugged it into my script and now have a timer-based control over my child processes. very useful!

line:
echo Finished up at $(date -r $after)

should actually read:
echo Finished up at $(date -d $after)

-d displays the time given by input string.
-r displays the time given by reference "file".

Kept getting "file does not exist error", found out that the "-d" flag was causing error.

Thanks for the script... saved me a bit of sanity and time... and these days, we need all the sanity we can get.

b@

Hi iwant to set my server time automaticlly with conecting with ssh to another host ant get correct time and change my server time in crontb enviroment please help me thanks

Had to adjust the last line to get this to work for me -- final script below:

#!/bin/bash
before=$(date +%s)
echo Started : $(date)
# commands to time go here
after=$(date +%s)
elapsed_seconds=$(expr $after - $before)
echo Ended : $(date)
echo Elapsed time : $(date -d "1970-01-01 $elapsed_seconds sec" +%H:%M:%S)

Perfect!

I had a number of scripts that I wanted to track session time on, along with other time variations. I have been able to use all of the information provided here with success and "right-out-of-the-box".

Finally, I can call some of my scripts completed.

Thanks much!

I was unaware of the use of the date command figure elapsed time, but after looking at it I can see that it has a limitation that prevents my using it. As neat as it is, it only works for elapsed times of less than a day. There is no %DAYS option for elapsed days, if you need to monitor things that run that long (or can potentially run that long).

Luckily the shell date arithmetic is pretty simple. You don't even need 'bc'.

(( DIFF = NOW - START ))
(( DAYS = DIFF / 86400 ))
(( HOURS = DIFF % 86400 / 3600 ))
(( MIN = DIFF % 3600 / 60 ))
(( SEC = DIFF % 60 ))
ELAP=$(printf "%03d:%02d:%02d:%02d" $DAYS $HOURS $MIN $SEC)

The printf adds leading zeros so the columns don't float. Not as slick as 'date -d', but the code above works for about a year (which should cover anything in real life).

On some systems the folowing command, will give unwanted numbers in the hour column (below)

$ echo $(date -r 110 +%H:%M:%S)
19:01:50

This is because you're reporting elapsed time since the epoch, but if you're not on GMT, then the epoch won't start at 00:00:00. (On EDT you get 19:00:00 for 0). Therefore you need to report in UTC as follows:

$ echo $(date -u -r 110 +%H:%M:%S)
00:01:50

Very Nice!
exactly what I was looking for.
thanks.

Thanks Dave - exactly what I needed!