Meaning of _PC_PATH_MAX

[Donn Terry]

From:  Donn Terry <donn at hpfcdc.uucp>

>IEEE Std 1003.1-1988 paragraph 5.7.1.2 note 5 describes the value 
>returned by pathconf() when _PC_PATH_MAX is used as an argument as, 
>"The maximum length of a relative pathname when the specified 
>directory is the working directory."

>I have tried this on several POSIX.1 systems.  None of them seem to 
>enforce the maximum.  In fact they all return a constant (say, 1024) 
>even if the path given to pathconf() is already longer than that.

>Is this conforming behavior?

>If it is conforming, how should a portable application determine the 
>longest pathname a user can specify?  

This is hard to get a clear reading on from what you have written.  It
could either be sloppy implementation or perfectly conformant.

POSIX specifically permits (in shell notation):
	cd /
	cd <1024 character pathname>
	cd <another such thing>
	...

There is no longest pathname a user can specify; there is a longest
one from / and from the current working directory.  Pathconf doesn't
worry about what the cwd is.

>What about _PC_NAME_MAX?  May readdir() return a longer name than the 
>value returned by pathconf() for that directory?

It shouldn't.  No location relative issues here.

Donn Terry
(As usual... speaking only for myself.)

Volume-Number: Volume 21, Number 79