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From: Chris Ahlstrom <OFeem1987@teleworm.us>
Newsgroups: comp.os.linux.advocacy
Subject: Re: Then there's PATH_MAX
Date: Tue, 10 Dec 2024 08:46:30 -0500
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Farley Flud wrote this post while blinking in Morse code:

> On Mon, 09 Dec 2024 06:09:40 +0000, vallor wrote:
>
>> #include <stdio.h>
>> #include <limits.h>
>> 
>> #ifdef __linux__
>> #include <linux/limits.h>
>> #endif
>> 
>> int main (void)
>> {
>> printf("%d\n",PATH_MAX);
>> return 0;
>> }
>
> This is bullshit.
>
> PATH_MAX is filesystem dependent and since GNU/Linux, unlike that
> pile of garbage Microslop, supports many, many different filesystems
> the PATH_MAX macro is unreliable and may be undefined on some machines.

According to Kerrisk's Linux API book, PATH_MAX has a minimum value of
255, and is named _PC_PATH_MAX by pathconf()/sysconf(). NAME_MAX has a
minimum value of 14. These values are somewhat unrealistic.

You can check out all the values defined:

    $ getconf -a &> variables.text

Here are a few:

    NAME_MAX                           255
    _POSIX_NAME_MAX                    255
    PATH_MAX                           4096
    _POSIX_PATH_MAX                    4096
    ARG_MAX                            2097152
    PAGESIZE                           4096
    PAGE_SIZE                          4096

> The best and only way to determine file name/path parameters is to
> use "pathconf" of "fpathconf:"
                 ^^ or
>
> https://pubs.opengroup.org/onlinepubs/9799919799/
>
> From the link:
>
> "The pathconf() function was proposed immediately after the sysconf() 
> function when it was realized that some configurable values may differ 
> across file system, directory, or device boundaries."

Note that the values provided by pathconf() or fpathconf() can change
over the lifetime of a process (e.g. when a different filesystem is mounted).

Anyway, for my application(s), including those running on Windows, I treat
PATH_MAX as a defining limit. We don't need no funking long pathnames!

-- 
!netgod:*! time flies when youre using linux
!doogie:*! yeah, infinite loops in 5 seconds.
!Teknix:*! has anyone re-tested that with 2.2.x ?
!netgod:*! yeah, 4 seconds now