Is 6,10-12 valid syntax fo the hour part of a cron task?

Question

I know that "10-12" is a valid range for the hour part of chron and that "6,7,8" is avlid syntax too.

Can I combine these 2 an us "6,10-12" if valid hours time is at 6 and between 10 and 12?

Answer 1

That depends on which cron daemon is in use.

Debian/Ubuntu ship with Vixie cron by default. The manual page for it (man 5 crontab) has this to say:

Ranges of numbers are allowed.  Ranges are two numbers separated
with a hyphen.  The specified range is inclusive.  For example,
8-11 for an ``hours'' entry specifies execution at hours 8, 9, 10
and 11.

And further...

Lists are allowed.  A list is a set of numbers (or ranges)
separated by commas.

So for this particular implementation, "6,10-12" would be valid as it is a list containing a number and a range, and a range can include lists.

If you are unsure, man 5 crontab should provide clarity.