cal (command)

cal is a command-line utility on a number of computer operating systems including Unix, Plan 9, Inferno and Unix-like operating systems such as Linux that prints an ASCII calendar of the given month or year. If the user does not specify any command-line options, cal will print a calendar of the current month. The command is a standard program on Unix and specified in the Single UNIX Specification.

cal
Developer(s)Charles Dye
Initial releaseNovember 3, 1971 (1971-11-03)
Written inPlan 9: C
FreeDOS: x86 assembly language
Operating systemUnix, Unix-like, Plan 9, Inferno, MSX-DOS, FreeDOS
PlatformCross-platform
TypeCommand
Licenseutil-linux: BSD-4-Clause
FreeDOS: Freeware / Source-available software
Plan 9: MIT License

Implementations

The cal command was present in 1st Edition Unix. A cal command is also part of ASCII's MSX-DOS2 Tools for MSX-DOS version 2.[1] It is also available for FreeDOS. This implementation only supports the Gregorian calendar (New Style) and may be distributed freely, with or without source. The FreeDOS version was developed by Charles Dye.[2]

Examples

 
$ cal
      March 1984                    
 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 31

$ cal -3 (shows the previous, current and next month)
     June 2022             July 2022            August 2022       
Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  
          1  2  3  4                  1  2      1  2  3  4  5  6  
 5  6  7  8  9 10 11   3  4  5  6  7  8  9   7  8  9 10 11 12 13  
12 13 14 15 16 17 18  10 11 12 13 14 15 16  14 15 16 17 18 19 20  
19 20 21 22 23 24 25  17 18 19 20 21 22 23  21 22 23 24 25 26 27  
26 27 28 29 30        24 25 26 27 28 29 30  28 29 30 31

$ cal 2023
                            2023
      January               February               March          
Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  
 1  2  3  4  5  6  7            1  2  3  4            1  2  3  4  
 8  9 10 11 12 13 14   5  6  7  8  9 10 11   5  6  7  8  9 10 11  
15 16 17 18 19 20 21  12 13 14 15 16 17 18  12 13 14 15 16 17 18  
22 23 24 25 26 27 28  19 20 21 22 23 24 25  19 20 21 22 23 24 25  
29 30 31              26 27 28              26 27 28 29 30 31     
                                                                  
       April                  May                   June          
Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  
                   1      1  2  3  4  5  6               1  2  3  
 2  3  4  5  6  7  8   7  8  9 10 11 12 13   4  5  6  7  8  9 10  
 9 10 11 12 13 14 15  14 15 16 17 18 19 20  11 12 13 14 15 16 17  
16 17 18 19 20 21 22  21 22 23 24 25 26 27  18 19 20 21 22 23 24  
23 24 25 26 27 28 29  28 29 30 31           25 26 27 28 29 30     
30                                                                
        July                 August              September        
Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  
                   1         1  2  3  4  5                  1  2  
 2  3  4  5  6  7  8   6  7  8  9 10 11 12   3  4  5  6  7  8  9  
 9 10 11 12 13 14 15  13 14 15 16 17 18 19  10 11 12 13 14 15 16  
16 17 18 19 20 21 22  20 21 22 23 24 25 26  17 18 19 20 21 22 23  
23 24 25 26 27 28 29  27 28 29 30 31        24 25 26 27 28 29 30  
30 31                                                             
      October               November              December        
Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  
 1  2  3  4  5  6  7            1  2  3  4                  1  2  
 8  9 10 11 12 13 14   5  6  7  8  9 10 11   3  4  5  6  7  8  9  
15 16 17 18 19 20 21  12 13 14 15 16 17 18  10 11 12 13 14 15 16  
22 23 24 25 26 27 28  19 20 21 22 23 24 25  17 18 19 20 21 22 23  
29 30 31              26 27 28 29 30        24 25 26 27 28 29 30  
                                            31

$ cal 5 2014
      May 2014        
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 31

Quirks (1752)
Further information: Calendar (New Style) Act 1750
$ cal 9 1752
  September 1752
 S  M Tu  W Th  F  S
       1  2 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30

The Gregorian calendar reform was adopted by the Kingdom of Great Britain, including its possessions in North America (later to become eastern USA and Canada), in September 1752. As a result, the September 1752 cal shows the adjusted days missing. This month was the official (British) adoption of the Gregorian calendar from the previously used Julian calendar. This has been documented in the man pages for Sun Solaris as follows. "An unusual calendar is printed for September 1752. That is the month when 11 days were skipped to make up for lack of leap year adjustments."[3] The Plan 9 from Bell Labs manual states: "Try cal sep 1752." Date of adoption of the reform differs widely between countries so, for some users, this feature may be a bug. Special handling of 1752 is known to have appeared as early as the first edition of the Unix Programmer's Manual in 1971.[4]

See also

References
  1. "MSX-DOS2 Tools User's Manual - MSX-DOS2 TOOLS ユーザーズマニュアル". April 1, 1993 – via Internet Archive.
  2. "ibiblio.org FreeDOS Package -- cal (Unix-like)". www.ibiblio.org.
  3. "Synopsis - man pages section 1: User Commands". docs.oracle.com.
  4. Thompson, K.; Ritchie, D. M. (1971). Unix Programmer's Manual (First ed.). Bell Telephone Laboratories. pp. cal (VI).

Sources
  • Ray, Deborah S.; Ray, Eric J. (2010). "Calendaring with cal". In Gulick, Rebecca (ed.). Unix and Linux: Visual QuickStart Guide. Book Publishers. pp. 276–278. ISBN 9780132104470.
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