Linux Script- Date Manipulations

Question

I will set one date variable(Say \'08-JUN-2011\') and I want to do some calculations based on that date namely,
1. Have to get the first day of the given day\'s month.

Answer 1

Using dateutils' dround tool:

Current month:

$ dround today -1
2014-02-01

Previous month

$ dround today -31
2014-01-31

Last day of current month:

$ dround today +31
2014-02-28

Of course you can use a custom date instead of today, the idea is to round down or up to the desired day-of-the month, e.g. the next first-of-the-month given 2010-10-04:

$ dround 2010-10-04 +1d
2010-11-01