What does double slash // in `cd //` mean in Linux?

linux bash shell directory-structure cd
vitaut picture vitaut · Dec 19, 2013 · Viewed 20.8k times · Source

I've entered a command cd // instead of cd / by mistake and instead of getting an error as I'd expect the shell (Bash) showed a prompt as if I'm in the // directory:-

<username>@<hostname>://$
<username>@<hostname>://$ pwd
//

Listing the content of the directory shows that it is the same as /.

So what exactly cd // do and what's the difference from cd /?

Answer

Rahul Tripathi picture Rahul Tripathi · Dec 19, 2013

Actually it means nothing and is ignored.

From the Bash FAQ E10::

E10) Why does 'cd //' leave $PWD as '//'?

POSIX.2, in its description of 'cd', says that three or more leading slashes may be replaced with a single slash when canonicalizing the current working directory.

This is, I presume, for historical compatibility. Certain versions of Unix, and early network file systems, used paths of the form //hostname/path to access 'path' on server 'hostname'.

Also the Unix standards states:

A pathname that begins with two successive slashes may be interpreted in an implementation-defined manner, although more than two leading slashes shall be treated as a single slash.

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