How is the UNIX directory set up?

[Sean Eric Fagan]

In article <2265 at njitgw.njit.edu> gaines at mars.njit.edu (Starman) writes:
>Hi,
>	I'm working on reading in the directory from the . file. I've
>broken up the structire so far as follows:

Use opendir(), readdir() and closedir().  If they are not available on your
system, several pd or liberated versions exist in various places.

>Bytes 0-3 : file number
>Bytes 4-5 : File type
>Bytes 6-7 : filename length

Bzzt.

I know of three unix directory formats, two of which are:

Version 7:
	2 bytes	-- inode number
	14 bytes -- file name, padded out with nuls

BSD 4.2 and later:
	
	4 bytes -- inode number
	2 bytes -- directory entry length
	2 btyes -- name length
	<x> bytes -- name and possible 0 padding

Note that the byte counts are... well, they will probably be that size on
all machines.  The actual types for the BSD one are u_long, u_short,
u_short, and char.  BSD 4.3 and earlier do not allow filenames with 8-bit
characters (i.e., *real* ascii only), in addition to the other limits.

Whenever possible, try not to know the format of directories; it will only
cause problems.  In addition, if you have it, I also recommend the use of
pathconf() and fpathconf(); these can be used to, among other things, find
out the maximum filename length on the given (valid) path.  See POSIX
1003.1...

-- 
Sean Eric Fagan  | "I made the universe, but please don't blame me for it;
sef at kithrup.COM  |  I had a bellyache at the time."
-----------------+           -- The Turtle (Stephen King, _It_)
Any opinions expressed are my own, and generally unpopular with others.