In a POSIX directory a filename may
be as long as 255 characters selected from A-Z, a-z,
0-9, and dot ".", hyphen "-" or underscore "_". The
name may not start with a hyphen, but may start with any
other character. For example,
_txt_12a. are all valid names.
A POSIX name is case sensitive, so
not the same file as
with a hierarchy of directory names to produce the
absolute path of the file, a string of much greater
length may be created, up to 1023 characters in fact. Directories
are separated by a slash "/" character, for example,
The start of the POSIX directory is called the root directory and is represented by a slash "/". The root directory may contain files and directories under it. Any directory may contain other directories under it -- this is what makes it hierarchical. For example,
The special character "." by itself refers to the directory itself,
while ".." refers to the parent directory. For example,
./qedit-4.3.23 (look for the file in
the current directory) or
../src/list.c (go up
one level to the parent, then down to the
directory, then look for the file).
On MPE, some of these directories are the accounts of the old directory structure. An account directory may contain subdirectories which represent the groups of the old structure, but the accounts may also now contain POSIX subdirectories and files, and the groups may contain subdirectories as well. Only the directories which are accounts and groups need have valid MPE names. In order to merge the HFS into MPE's existing directory, there is one restriction: names directly below roots, accounts, or groups, are limited to 16 characters in length.