GeezerVison

cd / chdir
The cd command illustration (in a shell session in Debian GNU/Linux)
Developers	AT&T Bell Laboratories, MetaComCo, Microsoft, IBM, DR, Novell, HP, JP Software, ReactOS Contributors
Operating system	Unix, Unix-like, V, DOS, MSX-DOS, FlexOS, OS/2, TRIPOS, Windows, MPE/iX, Plan 9, Inferno, ReactOS, KolibriOS, SymbOS
Platform	Cross-platform
Type	Command

cd is a shell command that changes the working directory. It is available in many shells and other 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 chdir.

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) shells, and Microsoft shells including Command Prompt and PowerShell.

Other operating systems with shells supporting the command include OS/2,^[1] TRIPOS,^[2] AmigaOS^[3] (where the command is implied for an input path), ReactOS,^[4] DOSBox, and UEFI.^[5]

• On MS-DOS, the command is available in version 2 and later^[6]
• DR DOS 6.0 includes the command as both cd and chdir^[7]
• On HP MPE/iX the command is chdir^[8]
• On OpenVOS, the command is change_current_dir^[9]

Unlike many shell commands that are implemented as separate applications, change directory is often built-in to the shell because it affects the 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, tcsh, 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 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 CWD, but the functionality is available as cd in most command-line clients and some also provide lcd for changing the local working directory vs. the remote setting. The numerical computing environments MATLAB and GNU Octave include a change directory command as cd.^[10][11]

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 – which varies by program. In particular, Unix and Unix-like shells use a forward slash /, Command Prompt uses backslash \ 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 /user/bin/tmp, . refers to it and .. refers to /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 /usr/bin/tmp, cd ../../local specifies path /usr/local.

Starting with working directory set to the user's home (~), command ls followed by cd games might produce the following:

user@wikipedia:~$ ls
workreports games encyclopedia text.txt
user@wikipedia:~$ cd games
user@wikipedia:~/games$

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>

• Directory structure – Hierarchical structure of a computer's file system
• chroot – Shell command and system call that changes the apparent root directory
• List of command-line interpreters
• pushd and popd – Shell commands to save and restore the working directory
• pwd – Shell command that reports the working directory

• Wolverton, Van (1990). MS-DOS Commands: Microsoft Quick Reference, 4th Revised edition. Microsoft Press. ISBN 978-1-55615-289-4.
• John Paul Mueller (2007). Windows Administration at the Command Line for Windows Vista, Windows 2003, Windows XP, and Windows 2000. John Wiley & Sons. ISBN 978-0-470-16579-9.
• Barrett, Daniel J. (2012). Macintosh Terminal Pocket Guide: Take Command of Your Mac. O'Reilly. ISBN 978-1-4493-2898-6.

Wikibooks has a book on the topic of: Guide to Windows Commands

The Wikibook Guide to Unix has a page on the topic of: Commands

• Windows XP > Command-line reference A-Z > Chdir (Cd) from Microsoft TechNet
• cd: change the working directory – Shell and Utilities Reference, The Single UNIX Specification, Version 5 from The Open Group