How to clear shell command path cache?

All UNIX shells cache the command paths based on the contents of PATH enviromental variable. This can cause a problem if a cached path no longer exists.

For example, you have a command "foo" installed in /usr/bin and /usr/local/bin. Your PATH variable is set to "/usr/local/bin:/usr/bin".

When you run "foo", it is searched under each directory listed in PATH and the results are cached. In this case, the path "/usr/local/bin/foo" will be cached for "foo".

Now suppose you delete the command file "/usr/local/bin/foo". You still have another copy in "/usr/bin/foo". However, the next time you type "foo", the shell will return an error such as this:

 -bash: /usr/local/bin/foo: No such file or directory 

To clear the cached path of foo command, you can run

 $ PATH=$PATH 

This basically resets the PATH variable, thereby clearing the cache. * For bash shell, you might be able to do the same thing using

 $ hash -r 

Although, the previous method should also work for bash.

tags: command line  linux  

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