cd

cd stands for change directory and is a command used to switch the shell’s current working directory. In most Unix-like shells it is a builtin; it is not a separate program. Its primary purpose is to update the shell’s working directory for subsequent commands.

Its syntax is simple: cd [directory]. If directory is omitted, the command changes to the user’s home directory. If a dash is supplied (cd -), it returns to the previous directory in many Unix-like shells. Paths can be absolute or relative. Relative paths start from the current directory, while absolute paths begin at the filesystem root. Many shells support tilde expansion, so cd ~/projects goes to the projects folder in the home directory.

The command typically updates environment variables such as PWD to reflect the new working directory, and OLDPWD stores the previous one. The exact expansion rules and behavior can vary by shell, so users should consult their shell’s documentation for specifics.

Cross-platform notes: in Windows, the equivalent functionality is provided by the built-in cd command in Command Prompt and by Set-Location in PowerShell. Windows paths use backslashes and may require additional options to change drives (for example, /d in some contexts). In PowerShell, cd is an alias for Set-Location and generally supports similar navigation semantics.

Historically, cd has been a core feature of Unix shells since early implementations and remains a fundamental command for navigating the filesystem. It is commonly used together with commands such as pwd, pushd, and popd to manage directory context.