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Comment by foobeer | Hacker News Reader

Never knew about the "cal" command. I especially like that you can quickly look up a previous or future month/year. >> cal 3 1973 quickly shows a calendar of March 1973

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you can even look up `cal sept 1752`

Funny, 3-13 are missing here.

  > cal sep 1752
     September 1752     
  Su Mo Tu We Th Fr Sa  
         1  2 14 15 16  
  17 18 19 20 21 22 23  
  24 25 26 27 28 29 30

Edit: Oh, colour me surprised. https://en.wikipedia.org/wiki/September_14

This was the best thing I learned today

Right, you can use this to easily find the number of days in an arbitrary month in a script:

  % cal 2 1972 | tail +3 | wc -w
      29

tail: cannot open +3 for reading: No such file or directory

What am I doing wrong?

This worked like a charm though:

cal dec 2002 | tail -6 | wc -w

(since it always takes up 6 lines, even sep 1752)

It might be system-dependent. I'm on OSX and the command works properly.

The "+n" syntax is not standards compliant, from the tail info page (on fedora 19):

  On older systems, the leading '-' can be replaced by '+' in the obsolete option syntax with the same meaning as in counts, and obsolete usage overrides normal usage when the two conflict.  This obsolete behavior can be enabled or disabled with the '_POSIX2_VERSION' environment variable (*note Standards conformance::).

Aliasing to 'cal -3' can also be good if you want a little continuity.

The -3 arg is not available on OS X. Odd, since it's been in BSD Unix since forever. http://www.freebsd.org/cgi/man.cgi?query=cal

It's hardly ubiquitous.

NetBSD has had it for 11 years. FreeBSD has had it for three years and six months. DragonFly doesn't have it, OpenBSD doesn't have it...

http://cvsweb.netbsd.org/bsdweb.cgi/src/usr.bin/cal/cal.c?re... http://svnweb.freebsd.org/base?view=revision&revision=204697

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