What does //1/ mean

Question

QNX4 operating system using Korn Shell. This is in a .profile file.

export VARDIR=//1/usr/pvcs

What does the //1/ represent?

Answer 1

For the most part, multiple slashes are equivalent to a single slash. There's one exception: paths beginning with exactly two slashes (//foo/…, as opposed to /foo/… or ///foo/…) have a different meaning on some Unix variants. The meaning is often to access a remote resource with a path like //hostname/dir1/dir2/dir3/file. (Windows does this too, with \\hostname\dir1\dir2\dir3\file.)

QNX is one of those variants. On QNX4 with the FLEET distributed processing protocol, // followed by a number refers to that node. So //1/usr/pvcs on any node refers to the file /usr/pvcs on node 1.

(Source: the QNX6 manual, I can't find official QNX4 documentation online.)

Answer 2

To all indications, the variable is receiving a web path as content.

//aaaa/bbbb/cccc/nnnn - 
at where: 
aaaa = server name or IP address; 
bbbb = folder from the logical root of the domain aaaa (web servers can handle this dynamically); 
cccc = bbbb subfolder; 
nnnn = nth subfolder.