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Accepted
Stewie
Asked: 2011-09-29 11:24:44 +0800 CST

How to record time taken by a cron to execute.

  • 772

I have a cron set to run every minute 

* * * * * /usr/php /my/location/script.php

Now, I use time function to measure script execution time. So, running 

console$ time /usr/php /my/location/script.php

outputs

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

But it doesn't work with cron like this: 

* * * * * time /usr/php /my/location/script.php 2>&1 >> my_log_file

neither does it work on command line

console$ time /usr/php /my/location/script.php >> my_log_file

In both of the above examples, the time function actually calculates the time taken to write to my_log_file, instead of writing its output to the log file. Adding code in the script and recording STD OUTPUT is NOT AN OPTION.

linux logging cron

5 Answers

  1. Best Answer

    What about:

     * * * * *    (time /usr/php /my/location/script.php) >>my_log_file 2>&1
    • 9

  2. How about the in-built cron daemon feature?

    Check your cron daemon's man page. Many have a "-L" argument to specify a log level. Eg on Ubuntu (ie, Debian):

     -L loglevel
           Sets  the loglevel for cron. The standard logging level (1) will log the
           start of all the cron jobs. A higher loglevel (2) will cause cron to log
           also the end of all cronjobs, which can be useful to audit the behaviour
           of tasks run by cron. Logging will be disabled if the loglevel is set to
           zero (0).
    • 3

  3. The problem is using the time shell builtin vs. the time binary. Using the builtin it doesn't work, even with the proper redirection:

    $ time pwn >> foo 2>&1

real    0m0.003s
user    0m0.000s
sys 0m0.002s

$ cat foo 
/tmp

    Using the binary works:

    $ /usr/bin/time pwd >> foo 2>&1
$ cat foo 
/tmp
0.00user 0.00system 0:00.00elapsed 0%CPU (0avgtext+0avgdata 564maxresident)k
64inputs+8outputs (1major+175minor)pagefaults 0swaps

    With GNU time you can use the -o and -a options instead of shell redirection:

    $ /usr/bin/time -o foo -a pwd
/tmp
$ cat foo 
0.00user 0.00system 0:00.00elapsed 0%CPU (0avgtext+0avgdata 564maxresident)k
0inputs+0outputs (0major+179minor)pagefaults 0swaps
    • 2

  4. I would probably try putting

    /usr/bin/time /usr/php /my/location/script.php

    Into a script and then calling that script from your cron job.

    As an aside, is your php binary really in /usr? Or /usr/bin?

    • 0

  5. it seems time is bash builtin (at least on my system). Following works for me: /bin/bash -c 'time ls' > out.std 2> out.err. Output of time would be in stderr (out.err file).

    • 0