What is path //, how is it different from /?

Question

We know the root directory is /, and according to POSIX, there is another directory // which differs from /.

When you ls / and ls //, the output is the same, so is stat, however if you cd / and cd //, they are different, though the directory content are the same.

That really confused me. Anyone got an answer?

Umlaut

Can you provide a reference which says they are different? Also, what do you mean if you "cd /" vs. "cd //" they are different -- how do you know? – Tonsillotomy

@MarkkuK. Sorry I didn't say it clear, it means pwd didn't change. So as devnull said. You can try it. – Umlaut

Additionally, if you type "cd //usr" (for example) instead of "cd /usr", you end up in "/usr", bash says you are un "//usr" and pwd is "//usr" too... – Sematic

How does Linux handle multiple consecutive path separators (/home////username///file)? – Aquarium

Answer 1

From Bash FAQ, with formatting applied:

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.

Herald

On my git bash emulation (technically a windows machine) an attempt to ls -l // results in the machine trying to read and list the entire available network... wow. – Hepler