Open System Services Programmer's Guide

All OSS regular (data) files are odd-unstructured files. OSS regular files can be accessed using
Guardian functions and procedures as well as OSS functions.
File Access
Access to an OSS file or directory is determined by a set of permission bits associated with it. The
file owner, groups the owner belongs to, and others each have read, write, or execute permission
for a file.
For filesets that support OSS ACLs, access to an OSS file or directory is determined by the ACL.
For more information about OSS ACLs, see “Using OSS Access Control Lists (ACLs)” (page 259).
Access to Files on Remote NonStop Nodes
Any file visible to the OSS filesystem on a different node in an Expand network can be accessed
by preceding the file name of the name of a special directory. This special directory, which exists
just under the root directory, is called /E. The OSS pathname begins with /E, followed by the
node name and the absolute pathname of the file on the remote node. The directory is treated as
any another directory, and it includes all other nodes in the Expand network that support Open
System Services. (Guardian files are also accessible on those other nodes). Here is an example,
of a pathname for an OSS file named thatfile on a remote node named \COMM:
/E/comm/thatdir/thatfile
The pathnames of files on the local node also exist in /E as a special case. The directory
/E/localnode/ is a symbolic link to the local root directory /.
The Guardian File System
The Guardian file system consists of a limited number of levels. A complete (fully qualified) Guardian
file name has four components: a node name, volume name, subvolume name, and file identifier.
A node name begins with a backslash (\), and a volume name begins with a dollar sign ($).
Components are separated by a period (.). Figure 3 shows the components of the fully qualified
file name \mynode.$myvol.Mysubvol.myfile.
Figure 3 Components of Guardian File Names
Guardian file names visible to an OSS program are physical names: they refer to physical objects.
A node name refers to a physical node, and a volume name refers to a physical disk volume. A
node cannot contain nodes, a volume cannot contain volumes, and a subvolume cannot contain
subvolumes. The relationship between Guardian file names and physical devices is shown in
Figure 4.
30 Overview of the OSS Programming Environment