Re: a problem on crontab time format

[elbbit <elbbit@gmail.com>]

On 23/01/11 05:14, Kejia柯嘉 wrote:
> On Sun, Jan 23, 2011 at 12:11 AM, Kejia柯嘉 <w.kejia@gmail.com> 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