I recently discovered that a unix tool that I use on a daily basis is
practically unknown to most of the people I have asked about it. This
tool is cal(1):
$ cal
September 2020
Su Mo Tu We Th Fr Sa
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30
Yes, if run without any argument, cal(1) just prints the calendar of the
current month. But it can also print the calendar of any months in any
year:
$ cal 9 1972
September 1972
Su Mo Tu We Th Fr Sa
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
or the whole calendar of a year, if you see what I mean (i.e., if you
read the manpage). I think it is nowadays mainly forgotten because very
few people nowadays use a computer from the command line only (yes,
having a shiny calendar app is unfortunately the norm for many a "unix
enthusiast").
Just avoid to get confused with calendar(1), which will probably print
nothing at all in your system :P
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cal(1) appeared in UNIXv5 (1974)
calendar(1) appeared in UNIXv7 (1979)