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Run first Saturday of Month

This is not simple due to some wierd mechnices of day of week handling.

This works..

  0 0 1-7 * * [ `date +%u` -eq 6 ] && CMD

OR use

  0 0 * * 6 [ `date +%d` -le 7 ] && CMD


The day checks in the above is needed dur to a problem with crons

For example

  0 0 1-7  6  CMD

will acutally run the command on days 1 to 7 AND even saturday!!!
It is not just the first saturday of the month.

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Run on the LAST saturday of the month
A 'decent into madness'
  http://arstechnica.com/civis/viewtopic.php?f=16&t=34360

First attempts all fail...

 # july would run twice in 2010
 1 0 24-31 * 6 /some/script.sh

 # april would not run at all in 2010
 1 0 25-31 * 6 /some/script.sh

But this works..

 1 0 * * 6 [ `date +%d` -eq `echo \`cal | awk '{print $7}'\` | awk '{print $NF}'` ] && /some/script.sh

NOTE:
  echo `cal | awk '{print $7}'`
gets the day of saturdays for this month, all onto one line

Alternative for getting day of the last saturday
  cal | awk '{print $7}' | grep -E '[0-9]' | tail -n 1

Better recipe for last saturday...
  [ `date +%d` -eq `cal | awk '$7!=""{l=$7} END {print l}'` ] && CMD


Alternative using GNU date (depends on version)

to see if next saturday (in 7 days) is at start of mont
 0 0 * * 6 [ `date +%d -d '7 days'` -le '7' ] && CMD

or compare the month of next saturday...
 1 0 * * 6 [ `date +$m` -eq `date +%m -d "next Saturday"` ] && CMD


WARNING: some versions of "cal" starts on mondays, rather than sundays
use "cal -s" on those systems.

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