🚀 go-pugleaf

Submitted-by: willcox@urbana.mcd.mot.com (David A Willcox)

>Would someone who knows please tell me the relationship between the
>Standard C macro FILENAME_MAX and the POSIX macro _POSIX_PATH_MAX.

Since FILENAME_MAX is the longest possible filename string that can be
passed to fopen() and the like, it should be a value no smaller than
the largest possible value for PATH_MAX on your system.  It mustn't
ever be smaller than _POSIX_PATH_MAX, and would only be that small on
an implementation that only supported the minimum value for PATH_MAX
required by POSIX.

To quote from the C standard, FILENAME_MAX:

    ... expands to an integral constant expression that is the size needed
    for an array of char large enough to hold the longest file name
    string that the implementation guarantees can be opened. [There's
    a footnote saying that this doesn't mean that just any string this
    long is a valid file name.]

Since the C standard does not have any concept of directories, "file
name" in this context clearly corresponds to a POSIX path, not an
individual file name.

(Standard disclaimer stuff.  Motorola and POSIX disavow all knowledge of
my actions.)

David A. Willcox		"Just say 'NO' to universal drug testing"
Motorola MCD - Urbana		UUCP: ...!uiucuxc!udc!willcox
1101 E. University Ave.		INET: willcox@urbana.mcd.mot.com
Urbana, IL 61801		FONE: 217-384-8534


Volume-Number: Volume 23, Number 25

Submitted-by: karish@mindcraft.com (Chuck Karish)

In article <127638@uunet.UU.NET> steve@unidata.ucar.edu (Steve Emmerson) writes:
>Would someone who knows please tell me the relationship between the
>Standard C macro FILENAME_MAX and the POSIX macro _POSIX_PATH_MAX.
>
>In particular, should they be the same, or should FILENAME_MAX
>correspond instead to _POSIX_NAME_MAX.

_POSIX_PATH_MAX is more appropriate.  Standard C has no notion of a
path prefix.  Clause 4.9.1 of both the Standard and its rationale
tells us that a buffer of FILENAME_MAX characters should hold
the entire file name (what POSIX.1 would term the 'path').

	Chuck Karish		karish@mindcraft.com
	Mindcraft, Inc.		(415) 323-9000


Volume-Number: Volume 23, Number 26

Submitted-by: willcox@urbana.mcd.mot.com (David A Willcox)

>>Would someone who knows please tell me the relationship between the
>>Standard C macro FILENAME_MAX and the POSIX macro _POSIX_PATH_MAX.

>_POSIX_PATH_MAX is more appropriate.  Standard C has no notion of a
>path prefix.  Clause 4.9.1 of both the Standard and its rationale
>tells us that a buffer of FILENAME_MAX characters should hold
>the entire file name (what POSIX.1 would term the 'path').

_POSIX_PATH_MAX is probably not the correct value, unless your
implementation never supports anything larger than the minimum
required by POSIX.  PATH_MAX would be better, if it's defined on your
implementation (implying that you don't need to call pathconf() to get
a path-specific value).  If PATH_MAX isn't defined, then FILENAME_MAX
must be no smaller than the largest value you can get from
pathconf(_PC_PATH_MAX,...).

David A. Willcox		"Just say 'NO' to universal drug testing"

[ Standards are such lovely things... -mod ]

Volume-Number: Volume 23, Number 28