Re: a problem on crontab time format

Thanks a lot. I just think it's at least a `weak' bug: Any crontab
item specifying the minute slot as `*' may be a potential disaster.


On Sun, Jan 23, 2011 at 00:32, elbbit <elbbit@xxxxxxxxx> wrote:
On 23/01/11 05:14, Kejia柯嘉 wrote:
On Sun, Jan 23, 2011 at 12:11 AM, Kejia柯嘉 <w.kejia@xxxxxxxxx> wrote:
How does the following crontab line run:
* 1 * * * * my_command
Every minute of every 1 o'clock? Or only once of every 1 o'clock?
Sorry, the crontab line is:
 * 1 * * * my_command


You need to understand how cron(8) matches the time code you set in the
configuration file.  To re-iterate the man page available with "man 5
crontab":

   field          allowed values
   -----          --------------
   minute         0-59
   hour           0-23
   day of month   1-31
   month          1-12 (or names, see below)
   day of week    0-7 (0 or 7 is Sun, or use names)

A field may be an asterisk (*), which always stands for ``first-last''.

So, using the above as a guide, I approximate a translation of your
configuration line as saying: "at every minute of the hour 1 on every
day of month and during every month and on every day of the week please
run command my_command"

Hope this helps.

--

elbbit


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