Shell Programming and Scripting

The following bash command line works for the last day of the month. Test by replacing the 1 with tomorrows day of month number

Code:

[ 1 == `date +%d -d '1 day'` ] && echo "Day before tomorrow"

Can it be used within crontab? As

Code:

*  * 28-31 *  *  [  '1' == `date +\%d -d '1 day'` ] && echo "Today ls last day of month" >>/tmp/crontabtest

I tried to test crontab with the above entry (forcing dates) and I was was not able to get results

What operating system are you using?

When the command works from the command line, what is the output from the command?:

Code:

type date

Do you really want to run this command every minute of every hour 1 to 4 days every month?

The correct syntax for a numeric comparison in [ expression ] is:

Code:

[ 1 -eq `date +%d -d '1 day'` ]

not:

Code:

[ 1 == `date +%d -d '1 day'` ]

assuming that the date utility found on the system's default $PATH setting accepts a -d option on your system.

date +%d prints 01 on the 1st; which is not the same as 1 when performing a string comparison. You could also try a string comparison (which should use =; not ==), if you use date +%e instead of %d:

Code:

[ 1 = `date +%e -d '1 day'` ]

and this is probably safer than a numeric comparison. (Note that:

Code:

[ 1 -eq `date +%d -d '1 day'` ]

will give you a syntax error in some shells on the 8th and 9th days of the month because 08 and 09 are not valid octal values.)