OLDPWD

OLDPWD is an environment variable used by Unix shells to store the previous working directory during a shell session. It typically holds the value of the previous PWD before the most recent directory change.

Whenever a change directory command (cd) is executed, the shell updates OLDPWD to the old PWD and sets PWD to the new current directory. If the shell is started in a directory, OLDPWD is the directory you were in before your last cd command. The exact behavior can vary by shell, but this is the common pattern.

One of the primary uses of OLDPWD is with the shorthand command cd -, which switches to OLDPWD and prints the new current directory. Scripts may read OLDPWD to recover the previous location after performing operations in another directory.

In terms of scope, OLDPWD is typically an environment or shell variable. Some shells export OLDPWD to child processes, but not all. If OLDPWD is unset, cd - may fail or not work as intended, depending on the shell.

POSIX shells generally provide PWD and may provide OLDPWD; its presence is not guaranteed across all environments. Users should not rely on OLDPWD existing unless documented for their shell.