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E-Rick
Asked: 2020-11-21 00:55:13 +0800 CST 2020-11-21 00:55:13 +0800 CST

How do I program crontab to run a task on the last day of the month?

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I'm looking around how to schedule a task for the last day of the month. But I find very twisted solutions like this:

[code language="bash"]59 23 28-31 * * [ "$(date +%d -d tomorrow)" = "01" ] && execute_this[/code]

There has to be a more readable solution!!!

linux

2 Answers

  1. Best Answer

    You could break it down to make it a bit more readable like this:

    # min  hr  date     month          dow
  59   23  31     1,3,5,7,8,10,12   * execute_this
  59   23  30     4,6,9,11          * execute_this
  59   23  28,29  2                 * execute_this

    You could also pass the date validation to a small script and run:

    59 23 28-31 * * check_date.sh && execute_this

    Some crons, like Quartz, also implement the "L" flag, which represents the last day of the month, and is used such that:

    0 59 23 L * execute_this

    Quartz Font :Special-characters

    I hope this helps you.

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  2. It is not a very twisted solution, in fact it is one of the most simple, complete, concrete and elegant.

    Which means:

    # min  hour day month dow  command
   01   00   *    *    *   [ "$(date +%d -d tomorrow)" = "01" ] && instruccion

    It's simple, it's

    Executes every so many: minutes, hour, days of the month, months, days of the week, the following sequence of instructions

    And the sequence of instructions is made up of two: the first is a validation that asks "Tomorrow is the day such that it is 01?", since if tomorrow is day 01, then today is the last day of the month

    If it passes that instruction then it will return true and the following instructions will be executed.

    That way you don't have to write everything @JoseVelasco did for the crontraditional part.

    The command date +%d -d tomorrowuses the command dateto get the "day after tomorrow" ( -d tomorrow) but with the numeric format of the number of the day ( +%d), so comparing that result with "01", we would be asking if " Tomorrow is the first of the next month ? " which is equivalent to asking "Is today the last day of the month ?".

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