cal (command)

cal
	The cal command as shown in a Linux zsh session in Arch Linux
Developer(s)	Charles Dye
Initial release	November 3, 1971; 52 years ago
Written in	Plan 9: C; FreeDOS: x86 assembly language
Operating system	Unix, Unix-like, Plan 9, Inferno, MSX-DOS, FreeDOS
Platform	Cross-platform
Type	Command
License	util-linux: BSD-4-Clause; FreeDOS: Freeware / Source-available software; Plan 9: MIT License

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.

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
    February 2024                   
 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

$ 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 6 2023
      June 2023        
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

Quirks (1752)

$ 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]

References

^ "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.
^ "ibiblio.org FreeDOS Package -- cal (Unix-like)". www.ibiblio.org.
^ "Synopsis - man pages section 1: User Commands". docs.oracle.com.
^ Thompson, K.; Ritchie, D. M. (1971). Unix Programmer's Manual (First ed.). Bell Telephone Laboratories. pp. cal (VI).

cal: print a calendar – Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group

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.

External links

cal(1) – Plan 9 Programmer's Manual, Volume 1
cal(1) – Inferno General commands Manual
cal(1) – Linux User Commands Manual
cal(1) – FreeBSD General Commands Manual
cal(1) – NetBSD General Commands Manual
cal(1) – OpenBSD General Commands Manual
Source of explanation of cal 9 1752 phenomena (humor)

[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).

[1]

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v t e Unix command-line interface programs and shell builtins
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Shell builtins	alias cd echo test unset wait
Searching	find grep
Documentation	man
Software development	ar ctags lex make nm strip yacc
Miscellaneous	bc cal expr lp od sleep true and false
Categories Standard Unix programs Unix SUS2008 utilities List

v t e Plan 9 command-line interface programs and shell builtins
File system	chmod chgrp cmp cp dd du file gzip ls mkdir pwd rm split tee touch
Processes	kill ps
User environment	passwd who
Text processing	awk basename comm diff ed eqn join sed sort spell strings tail tr troff uniq wc
Shell builtins	echo test
Networking	ip/ipconfig ip/ping netstat
Searching	grep
Software development	ar hoc lex nm strip yacc
Miscellaneous	bc cal fortune sleep
Category

v t e Digital calendars
Standards	iCalendar CalDAV DAViCal Web Calendar Access Protocol Webcal Related standards: SyncML vCard WebDav
Current implementations	30 Boxes Any.do Artist Growth Cal (command) Calendar (Apple) Calendar (Windows) Cozi Central DAViCal Hiri EM Client EProductivity Evolution Google Calendar Holiline Reminder Ical (Unix) Kontact Lanyrd Mail (Windows) Meeting Maker Microsoft Outlook Web Outlook.com Lightning Sunbird Rainlendar Remember the Milk SabreDAV Sun Java System Calendar Server Oracle Communications Unified Communications Suite Upcoming Yahoo! Calendar Windows Live Mail wmCalClock
Discontinued	Chandler Ecco Pro HotJava Views Microsoft Entourage MobileMe Mozilla Calendar Project Now Up-to-Date Plan Sunrise Calendar Tempo Windows Mobile Device Center