Unix convert Month name to number

Question

In BASH shell scripting or using gdate, given a date like "Oct 2011" how do I convert to a year-month number format? Output should be "2011-10", for example.

Answer 1

mydate="Oct 2011"
date --date="$(printf "01 %s" $mydate)" +"%Y-%m"

The parse_datetime interface for GNU date (which is what the example uses) has lots of rules. the Oct 2011 form of the date isn't one of them, so you prepend a "01 " to the front of it and date likes it.

Answer 2

read mon year <<< "Oct 2012"
date -d "$mon 1 $year" "+%Y-%m"

Result:

2012-10