Shell Programming and Scripting

Hi again,

I need to delete stats on every 2nd Sunday and I've try the following codes but unfortunately it didn't work. I'll really appreciate as always for your help. I'm on FreeBSD 8.2-STABLE.

altsun.sh script:

Code:

#!/bin/sh
day = $(`date '+%e'`)
if [ $day -ge 8 -a $day -le 14 ] then
   rm /home/user/tst/statsmod.dat
else
exit
fi

Code:

59 23 * * 0 /home/user/altsun.sh >/dev/null 2>&1

Sincerely Regards,
user

If your cut/paste is accurate, your problem is likely because you have spaces round the equal sign in the assignment of day:

Code:

day = $(`date '+%e'`)

However, I question your logic. Deleting your file only when the execution day is the 8th through the 14th only cleans up once per month. If you want to delete every other week, wouldn't it be better to delete when the week number is either odd or even?

Code:

if (( $(date +%U ) % 2 ))
then
    rm some-log-file
else
   exit 0
fi

The above should delete on odd weeks and should do the right thing when there are 5 Sundays in a month.

Thanks so much agama! I like your approach and will try it. Thanks again

Hello agama,

I have tried your codes past two sundays and I was expecting on 06/03/2012 (it was odd sunday) the script should have deleted the stats but it seems it didn't work. Am i missing something?

cron:

Code:

59 23 * * 0 /home/user/altsun.sh >/dev/null 2>&1

altsun.sh:

Code:

#!/bin/sh

if (( $(date +%U ) % 2 ))
then
   rm /home/user/tst/statsmod.dat
else
   exit 0
fi

Thanks again
best regards
user

I don't think so.

Given that it's an "odd week" all week, what happens if you run this script?

Code:

if (( $(date +%U ) % 2 ))
then
   echo "it is an odd week and things should be removed"
else
   echo "it is an even week and things would not be removed"
fi

You can run this manually to see what is happening.

You might also want to redirect your output and stderr from the script to a file rather than /dev/null. If there's an error in the script you'll be able to catch it. The way you have it coded you'll be scratching your head if there is a problem. I always like to have a log of what is kicked off by cron and usually put echo statements at key points (deleting files, skipping files in this case) so as to document that the script was run, and to know what it thought it did. Also to capture any error messages along the way.

---------- Post updated at 22:03 ---------- Previous update was at 22:00 ----------

I just noticed that you're running it with #!/bin/sh. If on your system that points to a "real" Borne shell (and not a more recent shell), then the syntax $(...) and ((..)) might not be valid.

Try replacing #!/bin/sh with the path for bash or kshell (in addition to adding some logging).

agama, thanks for the reply

well i think bash or kshell won't work because i'm using freebsd (/bin/tcsh).

I'll definitely add logging as you have suggested. So it will work on next sunday.


thanks
user

Yes, if you don't install bash/kshell it's probably not there by default.

Given that, the /bin/sh on FreeBSD (at least on the 8.2 system I tested on) is a more Borne like (probably POSIX) shell, and it's likely tripping over the if expression. When I tested your original code it evaluated the expression, but then tried to execute the result (1) rather than treating that as true. I just tried the code below and it seems to do just fine:

Code:

#!/bin/sh

w=$(( $(date "+%U") % 2 ))
if [ $w -ne 0 ]
then
        echo odd week
else
        echo even week
fi

You might want to try changing your script to something like this. You could always code a dummy script (with echo statements rather than the rm statement), and set it off from cron before next Sunday rather than waiting all week.