Creating a RFC 1123 compliant date for HTTP header creation on the CLI

Question

I'm trying to create a HTTP 1/1 compliant date header using standard unix date(1) in order to post this to a RESTful server using curl or similar.

Any ideas what format to pass to date(1) to get this to be RFC 1123 compliant?

Many thanks

Answer 1

man date for whatever version of date your OS provides and use the correct switches to print (see man strftime), from from left to right, with a space between each, first the date:

Day (Three letter abbreviation Mon-Tue-Wed...) followed by a comma ,,
the month (Three letter abbreviation Jan Feb Mar ...)
the year (4 digit notation 1970, 1971 ...)
and then time HH:MM:SS.

And you might get something like Fri, 20 May 2016 20:22:33 GMT

Answer 2

env TZ=GMT; date '+%a, %d %b %Y %T %Z'

1. %T is equivalent to %H:%M:%S.
2. %Z is replaced by the time zone name.

The solution by @brad, DATE=$(date -u +%a,\ %d\ %b\ %Y\ %H:%M:%S\ GMT), would be incorrect if the time zone setting of your system is not GMT. For example:

env TZ=Asia/Taipei; date -u +%a,\ %d\ %b\ %Y\ %H:%M:%S\ GMT

%H:%M:%S would be GMT+8 while the output is GMT, but should be CST.