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Can cron do this?


 
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# 1  
Question Can cron do this?

Can cron run a script on the 4th Saturday of the month, every month? I don't believe it can.

Here's what I have so far:

30 5 24-31 * 6 <command>
# 2  
The syntax you show really should work, but it doesn't. It will run your script on each day of 24 through 31 and on each Saturday. This interpretation of the cron fields arose in System V and everyone who had right conformed.

Your math is off though. The 4th Saturday must occur on the 22 through the 28.

Try this:
30 5 * * 6 [ `date +%e` -gt 21 -a `date +%e` -lt 29 ] && <command>
# 3  
I did as you suggested but get this error:

sh: test: 0403-021 A ] character is missing.

Here is my syntax (modified for testing today):

57 13 * * 4 [ `date +%e` -gt 8 -a `date +%e` -lt 11 ] && mail -s "cron test" me@homer.com < /users/me/test.txt

Any ideas?
# 4  
I have actually put code in a crontab and I too am getting the same error. That is odd since we have some very similiar tests in working crontabs. I don't have time to dig into now, but I will soon. In the meantime you could write a script called week4 that returns 0 or 1 depend on the week. And then use
week4 && command

This has actually exposed a very interesting problem. Right now I'm thinking that cron jobs are pumped through a proto file just like at jobs.
# 5  
There seem to be two issues: first everything after a per cent sign is getting truncated. You would think that I would have encountered a cron command before that used a %, but I guess that this must be my first. Also the backtick expressions are not being evaluated.

The syntax that works for me is:
* * * * * eval [ `date +\%e` -gt 8 -a `date +\%` -lt 11] && <command>

This is ugly enough that some cool script is needed. I'll write one this weekend.
# 6  
Excuse my continuing monologue Smilie

Anything after a % is stripped off a cron command and is feed as standard input into the command. This is mentioned on crontab(1) manpage. SunOS even has an example on their manpage.
# 7  
Bug

Thanks. I will test and advise.

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