whence

The whence command line tool is commonly used in Unix-based systems to locate executable files or commands in the shell's search path. It is similar to the which command but offers some additional functionality.

When you run whence followed by a command, it reports the location of the command. This is particularly useful when multiple versions of a command are installed and you want to know the exact path of the command you are using.

The output of whence also includes additional information such as the type of the command (built-in, function, alias, or executable file) and whether the command is hashed (previously looked up and stored for faster future reference).

Additionally, whence allows you to search for command names that match a given pattern or regular expression, making it helpful for finding commands based on partial names or specific patterns.

In some Unix shells, like zsh, whence is a built-in command, while in others, it may be an external command provided by the shell's corresponding package.

Overall, whence is a versatile command line tool that assists users in quickly identifying the location and details of commands within their shell environment.