Double root folder vs single root folder

From 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'.

"It's not a bug, it's a feature!"

You're still in the same root directory. I don't know the origins of this, but suspect it may have something to do with building strings for absolute paths. If anyone else knows for sure, pipe up.

Multiple slashes are just ignored by the tools you have used and you are always getting to the same root folder.

Multiple slashes are treated as a single slash for pathname-resolution purposes.

What you're seeing in the shell prompt is an artifact of bash PS1 handling (see section "PROMPTING" in the bash manpage).

[root@linux /]# cd /    ; echo $PWD
/
[root@linux /]# cd //   ; echo $PWD
//
[root@linux //]# cd /// ; echo $PWD
/
[root@linux /]# cd //// ; echo $PWD
/

The result is only a matter of presentation; you're always in the same root directory. You can check this by looking at /proc/$$/root.

[edit] Well I never knew this: http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap04.html#tag_04_11 The meaning of "//" is left undefined by the standards, but "///" and more slashes are equivalent to "/".