Editing Cd (command)

{{Short description|Command to change the working directory}}
{{lowercase}}
{{Infobox software
| name = cd / chdir
| logo = 
| screenshot = Cd command.png
| screenshot size = 
| caption = The {{code|cd}} command illustration (in a shell session in [[Debian GNU]]/[[Linux]])
| developer = [[AT&T Bell Laboratories]], [[MetaComCo]], [[Microsoft]], [[IBM]], [[Digital Research|DR]], [[Novell]], [[Hewlett-Packard|HP]], [[JP Software]], [[ReactOS]] Contributors
| released = 
| latest release version = 
| latest release date = 
| operating system = [[Unix]], [[Unix-like]], [[V (operating system)|V]], [[DOS]], [[MSX-DOS]], [[FlexOS]], [[OS/2]], [[TRIPOS]], [[Microsoft Windows|Windows]], [[HP Multi-Programming Executive|MPE/iX]], [[Plan 9 from Bell Labs|Plan 9]], [[Inferno (operating system)|Inferno]], [[ReactOS]], [[KolibriOS]], [[SymbOS]]
| platform = [[Cross-platform]]
| genre = [[Command (computing)|Command]]
| license = 
| website = 
}}
'''{{code|cd}}''' is a [[Shell (computing)|shell]] [[command (computing)|command]] that changes the [[working directory]]. It is available in many shells and other [[application software|applications]] that maintain a working directory. In some contexts, the command can perform actions other than change directory. Some environments provide the change directory feature via a different command name such as {{code|chdir}}.

== Implementations ==
Generally, a computer system that provides access to a [[hierarchical file system]], provides a change directory command to set the working directory. As this applies to most operating system shells, most support a change directory command, including [[Unix]] and [[Unix-like]] (i.e. [[Linux]]) [[Unix shell|shells]], and [[Microsoft]] shells including [[Command Prompt]] and [[PowerShell]].

Other operating systems with shells supporting the command include [[OS/2]],<ref>{{cite web|url=http://www.jatomes.com/Help/Os2Cmd.php#CD|title=JaTomes Help – OS/2 Commands|website=www.jatomes.com|access-date=2019-08-11|archive-date=2019-04-14|archive-url=https://web.archive.org/web/20190414130029/http://www.jatomes.com/Help/Os2Cmd.php#CD|url-status=dead}}</ref> [[TRIPOS]],<ref>{{cite web|url=https://www.pagetable.com/docs/amigados_tripos/tripos_manuals.pdf |title=Introduction to Tripos |access-date=2020-05-01}}</ref> [[AmigaOS]]<ref>{{cite book|url=http://archive.org/details/1988-rugheimer-spanik-amigados-quick-reference|title=AmigaDOS quick reference|first1=Hannes|last1=Rügheimer|first2=Christian|last2=Spanik|date=May 1, 1988|publisher=Grand Rapids, Mi : Abacus|isbn=9781557550491|via=Internet Archive}}</ref> (where the command is implied for an input [[Path (computing)|path]]), [[ReactOS]],<ref>{{cite web|url=https://github.com/reactos/reactos/blob/master/base/shell/cmd/internal.c|title=Reactos/reactos|website=GitHub|date=3 January 2022}}</ref> [[DOSBox]], and [[Unified Extensible Firmware Interface|UEFI]].<ref name="EFI-Shells-and-Scripting">{{cite web
 | url = http://software.intel.com/en-us/articles/efi-shells-and-scripting/
 | title = EFI Shells and Scripting
 | publisher = [[Intel]]
 | access-date = 2013-09-25
}}</ref> 

* On [[MS-DOS]], the command is available in version 2 and later<ref name="RUNNINGMSDOS">{{Cite book|author-last=Wolverton|author-first=Van|title=Running MS-DOS Version 6.22 (20th Anniversary Edition), 6th Revised edition|date=2003|publisher=[[Microsoft Press]]|isbn=0-7356-1812-7}}</ref> 
* [[DR DOS 6.0]] includes the command as both {{code|cd}} and {{code|chdir}}<ref name="drdos6userguide">{{Cite web |url=https://www.4corn.co.uk/archive/docs/DR%20DOS%206.0%20User%20Guide-opt.pdf |title=DR DOS 6.0 User Guide Optimisation and Configuration Tips |access-date=2019-08-13 |archive-url=https://web.archive.org/web/20190930135943/http://www.4corn.co.uk/archive/docs/DR%20DOS%206.0%20User%20Guide-opt.pdf |archive-date=2019-09-30 |url-status=dead }}</ref>
* On [[Hewlett-Packard|HP]] [[HP Multi-Programming Executive|MPE/iX]] the command is {{code|chdir}}<ref>{{Cite web|url=http://www.teamnaconsulting.com/compresources/pdfs/c01687363.pdf|title=MPE/iX Command Reference Manual|access-date=2018-10-21|archive-date=2018-10-21|archive-url=https://web.archive.org/web/20181021232213/http://www.teamnaconsulting.com/compresources/pdfs/c01687363.pdf|url-status=dead}}</ref> 
* On [[Stratus VOS|OpenVOS]], the command is {{code|change_current_dir}}<ref>{{cite web |url=http://stratadoc.stratus.com/vos/19.1.0/r098-19/wwhelp/wwhimpl/common/html/r098-19.pdf |title= OpenVOS Commands Reference Manual |website=stratadoc.stratus.com |access-date=2020-09-12}}</ref>

Unlike many shell commands that are implemented as separate [[application software|applications]], change directory is often built-in to the shell because it affects the [[State (computer science)|state]] of the shell whereas other commands modify system state outside the shell. If the command was implemented as a separate application, then the [[child process]] would need to modify state in the [[parent process]], but this is often prevented for safety. The command is built-in for most Unix shells ([[Bourne shell|Bourne]], [[tcsh]], [[Bash (Unix shell)|Bash]], etc.), Windows [[Command Prompt]] and [[PowerShell]], and MS-DOS [[COMMAND.COM]].

In a shell, the change directory command is typically implemented via a [[system call]] which on Unix and Unix-like systems is typically [[POSIX]] {{code|chdir()}} and on Windows is in the [[Windows API]]. 

The command is also provided in many programs other than shells. In the [[File Transfer Protocol]], the control stream command is {{code|CWD}}, but the functionality is available as {{code|cd}} in most command-line [[client (computing)|clients]] and some also provide {{code|lcd}} for changing the <u>l</u>ocal working directory vs. the remote setting. The [[numerical analysis|numerical computing]] environments [[MATLAB]] and [[GNU Octave]] include a
change directory command as <code>cd</code>.<ref>{{cite web|url=https://www.mathworks.com/help/matlab/ref/cd.html|title=Change current folder – MATLAB cd|website=www.mathworks.com}}</ref><ref>{{cite web|url=https://octave.sourceforge.io/octave/function/cd.html|title=Function Reference: cd|website=octave.sourceforge.io}}</ref>

== Use ==
Use of the command varies by context, but there are widespread similarities among variants. The examples below, mostly apply to Unix and Unix-like shells, PowerShell and Command Prompt.

To separate the directory names of a path, a program imposes command-line syntax such as a delimiting text between names {{endash}} which varies by program. In particular, Unix and Unix-like shells use a forward slash {{code|/}}, Command Prompt uses backslash {{code|\}} and PowerShell supports either. For simplicity, paths are shown with forward slashes here.

Commonly, a dot is short-hand notation for the working directory and two dots is short-hand for its parent. For example, given working directory {{code|/user/bin/tmp}}, {{code|.}} refers to it and {{code|..}} refers to {{code|/user/bin}}. The parent notation is often used to form a relative path that specifies a path that is both up and down the hierarchy. For example: starting with {{code|/usr/bin/tmp}}, {{code|cd ../../local}} specifies path {{code|/usr/local}}.

=== Common ===
Features that are commonly found for any change directory command:
* {{code|cd path/to/dir}} For a relative path (no leading slash), the path is appended to the working directory path; moving the context deeper into the directory tree hierarchy; for example, if the working directory is {{code|/usr}}, then {{code|cd bin}} changes the working directory to {{code|/usr/bin}}
* {{code|cd /path/to/dir}} For an absolute path (leading slash), the working directory is replaced with the specified path; for example, {{code|cd /bin}} sets the working directory to {{code|/bin}}
* {{code|cd ..}} Moves the directory tree context up one directory; for example, starting at {{code|/usr/bin/tmp}}, {{code|cd ..}} changes the working directory to {{code|/usr/bin}}
* {{code|cd .}} Does not change the working directory but is useful to recover after a directory is recreated by another process
* {{code|cd}} With no arguments, the command changes the working directory to the user's home directory; exception: Command Prompt reports the working directory path

=== Unix shells ===
Unix-based shells and PowerShell generally share these features:
* {{code|cd ~}} Changes the working directory to user's home directory
* <code>cd ~''username''</code> Changes the working directory to the specified user's home directory
* {{code|cd -}} Changes the working directory to the previous directory; for example, starting at {{code|/usr/bin/tmp}}, then {{code|cd /etc}}, and then {{code|cd -}} returns to {{code|/usr/bin/tmp}}; this supports toggling between two directories without [[pushd and popd]]

=== Legacy Microsoft shells ===
DOS maintains separate working directories for each [[Drive letter assignment|lettered drive]], and also has the concept of a current working drive. The {{code|cd}} command can be used to change the working directory of the working drive or another lettered drive. Typing the drive letter as a command on its own changes the working drive, e.g. {{code|C:}}; alternatively, {{code|cd}} with the {{code|/d}} switch may be used to change the working drive and that drive's working directory in one step.
Modern versions of Windows simulate this behaviour for backwards compatibility under [[CMD.EXE]].<ref>{{Cite web|url=https://devblogs.microsoft.com/oldnewthing/2010/10/11|title=October 11, 2010|website=The Old New Thing}}</ref>

== Example ==
[[File:chdir example.png|center|framed|Section of a Unix filesystem showing a user's [[home directory]] (represented as {{code|~}}) with a file and three subdirectories.]]

Starting with working directory set to the user's home ({{code|~}}), command <code>[[ls]]</code> followed by {{code|cd games}} might produce the following:

<syntaxhighlight lang="console">
user@wikipedia:~$ ls
workreports games encyclopedia text.txt
user@wikipedia:~$ cd games
user@wikipedia:~/games$
</syntaxhighlight>

A similar session in Command Prompt might look like:

 C:\> dir
 workreports        <DIR>       Wed Oct 9th   9:01
 games              <DIR>       Tue Oct 8th  14:32
 encyclopedia       <DIR>       Mon Oct 1st  10:05
 text        txt           1903 Thu Oct10th  12:43
 C:\> cd games
 C:\games>

== See also ==
* {{Annotated link|Directory structure}}
* {{Annotated link|chroot}}
* {{Annotated link|List of command-line interpreters}}
* {{Annotated link|pushd and popd}}
* {{Annotated link|pwd}}

== References ==
{{Reflist}}

== Further reading ==
*{{Cite book|author-last=Wolverton|author-first=Van|title=MS-DOS Commands: Microsoft Quick Reference, 4th Revised edition|date=1990|publisher=[[Microsoft Press]]|isbn=978-1-55615-289-4}}
*{{Cite book|author=John Paul Mueller|year=2007|title=Windows Administration at the Command Line for Windows Vista, Windows 2003, Windows XP, and Windows 2000|publisher=[[Wiley (publisher)|John Wiley & Sons]]|isbn=978-0-470-16579-9}}
*{{Cite book|first=Daniel J.|last=Barrett|year=2012|title=Macintosh Terminal Pocket Guide: Take Command of Your Mac|publisher=[[O'Reilly Media|O'Reilly]]|isbn=978-1-4493-2898-6}}

== External links ==
{{Wikibooks|Guide to Windows Commands}}
{{Wikibooks|Guide to Unix|Commands}}
* [https://technet.microsoft.com/en-us/library/bb490875.aspx Windows XP > Command-line reference A-Z > Chdir (Cd)] from [[Microsoft TechNet]]
* {{man|cu|cd|SUS|change the working directory}}

{{Unix commands}}
{{Windows commands}}
{{Portalbar|Free and open-source software}}

[[Category:Internal DOS commands]]
[[Category:File system directories]]
[[Category:Inferno (operating system) commands]]
[[Category:IBM i Qshell commands]]
[[Category:MSX-DOS commands]]
[[Category:OS/2 commands]]
[[Category:ReactOS commands]]
[[Category:Windows administration]]
[[Category:Standard Unix programs]]
[[Category:Unix SUS2008 utilities]]