How would I get a cron job to run every 30 minutes

Question

I m looking to add a crontab entry to execute a script every 30 minutes  on the hour and 30 minutes past the hour or something close  I have the following  but it doesn t seem to run on 0     30           What string do I need to use   The cron is running on OSX

User · Accepted Answer

Do   0 30         your command

User · Answer

You can use both of     OR divide     symbols  But      is better  Suppose the case of  every 5 minutes   If you use      you have to write the cron job as following   0 5 10 15 20 25 30 35                            your command   It means run your command in every hour in all of defined minutes  0 5 10     However  if you use      you can write the following simple and short job     5              your command   It means run your command in the  minutes that are dividable by 5 or in the simpler words   0 5 10      So  dividable symbol     is the best choice always

User · Answer

Try this   0 30         your command goes here   According to the official Mac OS X crontab 5  manpage  the   syntax is supported   Thus  to figure out why it wasn t working for you  you ll need to look at the logs for cron   In those logs  you should find a clear failure message   Note   Mac OS X appears to use Vixie Cron  the same as Linux and the BSDs

User · Answer

crontab does not understand  intervals   it only understands  schedule   valid hours  0-23 -- valid minutes  0-59  example  1  30         your command  this means  run when the minute of each hour is 30   would run at  1 30  2 30  3 30  etc   example  2    30         your command  this means  run when the minute of each hour is evenly divisible by 30   would run at  1 30  2 00  2 30  3 00  etc   example  3  0 30         your command  this means  run when the minute of each hour is 0 or 30   would run at  1 30  2 00  2 30  3 00  etc   it s another way to accomplish the same results as example  2  example  4  19         your command  this means  run when the minute of each hour is 19   would run at  1 19  2 19  3 19  etc   example  5    19         your command  this means  run when the minute of each hour is evenly divisible by 19   would run at  1 19  1 38  1 57  2 19  2 38  2 57 etc   note  several refinements have been made to this post by various users including the author

User · Answer

If your cron job is running on Mac OS X only  you may want to use launchd instead   From Scheduling Timed Jobs  official Apple docs       Note  Although it is still supported  cron is not a recommended solution  It has been deprecated in favor of launchd    You can find additional information  such as the launchd Wikipedia page  with a simple web search

User · Answer

You mention you are using OS X- I have used cronnix in the past  It s not as geeky as editing it yourself  but it helped me learn what the columns are in a jiffy  Just a thought

[linux] How would I get a cron job to run every 30 minutes?

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