Editing Cal (command)

{{lowercase title}}
{{Infobox software
| name                   = cal
| logo                   = 
| screenshot             = Cal screenshot.png
| screenshot size        = 
| caption                = The <code>cal</code> command as shown in a [[Linux]] [[Z shell|zsh]] session in [[Arch Linux]]
| developer              = Charles Dye
| released               = {{Start date and age|1971|11|3}}
| latest release version = 
| latest release date    = 
| programming language   = Plan 9: [[C (programming language)|C]]<br />FreeDOS: [[x86 assembly language]]
| operating system       = [[Unix]], [[Unix-like]], [[Plan 9 from Bell Labs|Plan 9]], [[Inferno (operating system)|Inferno]], [[MSX-DOS]], [[FreeDOS]]
| platform               = [[Cross-platform]]
| genre                  = [[Command (computing)|Command]]
| license                = [[util-linux]]: [[BSD-4-Clause]]<br />FreeDOS: [[Freeware]] / [[Source-available software]]<br />Plan 9: [[MIT License]]
| website                = 
}}
'''{{code|cal}}'''<!-- do not subst template: <code> tag breaks popups --> is a [[command-line interface|command-line]] utility on a number of computer [[operating system]]s including [[Unix]], [[Plan 9 from Bell Labs|Plan 9]], [[Inferno (operating system)|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 option]]s, <code>cal</code> 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 <code>cal</code> command was present in [[Research Unix|1st Edition Unix]]. A <code>cal</code> command is also part of [[ASCII Corporation|ASCII]]'s ''MSX-DOS2 Tools'' for [[MSX-DOS]] version 2.<ref>{{Cite web|url=https://archive.org/details/MSXDOS2TOOLS|title=MSX-DOS2 Tools User's Manual - MSX-DOS2 TOOLS ユーザーズマニュアル|date=April 1, 1993|via=Internet Archive}}</ref> 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.<ref>{{Cite web|url=https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/1.2/repos/pkg-html/cal.html|title=ibiblio.org FreeDOS Package -- cal (Unix-like)|website=www.ibiblio.org}}</ref>

==Examples==
<syntaxhighlight lang="console">
$ 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
</syntaxhighlight>

<syntaxhighlight lang="console">
$ 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
</syntaxhighlight>

<syntaxhighlight lang="console">
$ 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              
</syntaxhighlight>

<syntaxhighlight lang="console">
$ 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
</syntaxhighlight>

==Quirks (1752)==
{{more|Calendar (New Style) Act 1750}}
<syntaxhighlight lang="console">
$ 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
</syntaxhighlight>

The [[Gregorian calendar|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."<ref>{{Cite web|url=https://docs.oracle.com/cd/E26502_01/html/E29030/cal-1.html#scrolltoc|title=Synopsis - man pages section 1: User Commands|website=docs.oracle.com}}</ref> The [[Plan 9 from Bell Labs]] manual states: "Try {{mono|cal sep 1752}}." Date of adoption of the reform [[Adoption of the Gregorian calendar|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.<ref>{{Cite book |last=Thompson |first=K. |url=http://squoze.net/UNIX/v1man/man6/cal |title=Unix Programmer's Manual |last2=Ritchie |first2=D. M. |publisher=Bell Telephone Laboratories |year=1971 |edition=First |pages=cal (VI)}}</ref>

==See also==
* [[Cron]] – process for scheduling jobs to run on a particular date
* [[List of Unix commands]]

==References==
{{Reflist}}
{{Refbegin}}
* {{man|cu|cal|SUS|print a calendar}}
{{Refend}}
== Sources ==
* {{cite book |last1=Ray |first1=Deborah S. |last2=Ray |first2=Eric J. |date=2010 |editor-last=Gulick|editor-first=Rebecca |title=Unix and Linux: Visual QuickStart Guide |publisher=Book Publishers |pages=276–278 |chapter=Calendaring with cal|chapter-url=https://books.google.com/books?id=M-z1SWdCKkwC&dq=cal+linux&pg=PA276 |isbn= 9780132104470|name-list-style=}}

==External links==
{{Wikibooks|Guide to Unix|Commands}}
* {{man|1|cal|Plan 9}}
* {{man|1|cal|Inferno}}
* {{man|1|cal|die.net}}
* {{man|1|cal|FreeBSD}}
* {{man|1|cal|NetBSD}}
* {{man|1|cal|OpenBSD}}
* [https://web.archive.org/web/20160221144829/http://www.csd.uwo.ca/staff/magi/personal/humour/Computer_Audience/'cal%209%201752'%20explained.html Source of explanation of cal 9 1752 phenomena] (humor)

{{Unix commands}}
{{Plan 9 commands}}
{{Calendaring software}}

[[Category:Calendaring software]]
[[Category:Standard Unix programs|Cal]]
[[Category:Unix SUS2008 utilities]]
[[Category:Plan 9 commands]]
[[Category:Inferno (operating system) commands]]