[PATCH] man/man3/opendir.3: document that long file names result in ENAMETOOLONG

[PATCH] man/man3/opendir.3: document that long file names result in ENAMETOOLONG

[Collin Funk]

This behavior can be see with the following example program:

    $ cat main.c
    #include <string.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include <dirent.h>
    #include <errno.h>
    int
    main (int argc, char **argv)
    {
      if (argc < 2)
        return EXIT_FAILURE;
      DIR *dir = opendir (argv[1]);
      if (dir == NULL)
        {
          fprintf (stderr, "%s\n", strerror (errno));
          return EXIT_FAILURE;
        }
      closedir (dir);
      return EXIT_SUCCESS;
    }
    $ gcc main.c
    $ mkdir -p `python3 -c 'print("./" + "a/" * 32768)'`
    $ ./a.out `python3 -c 'print("./" + "a/" * 32768)'`
    File name too long

Signed-off-by: Collin Funk <collin.funk1@gmail.com>
---
 man/man3/opendir.3 | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/man/man3/opendir.3 b/man/man3/opendir.3
index a9af16269..6a5c7880f 100644
--- a/man/man3/opendir.3
+++ b/man/man3/opendir.3
@@ -73,6 +73,10 @@ .SH ERRORS
 .B EMFILE
 The per-process limit on the number of open file descriptors has been reached.
 .TP
+.B ENAMETOOLONG
+.I name
+was too long.
+.TP
 .B ENFILE
 The system-wide limit on the total number of open files has been reached.
 .TP
-- 
2.51.0

Re: [PATCH] man/man3/opendir.3: document that long file names result in ENAMETOOLONG

[Jakub Wilk]

* Collin Funk <collin.funk1@gmail.com>, 2025-10-17 01:18:
>    $ mkdir -p `python3 -c 'print("./" + "a/" * 32768)'`
>    $ ./a.out `python3 -c 'print("./" + "a/" * 32768)'`
>    File name too long

Simpler reproducer:

$ ./a.out $(printf '%0999d')
File name too long

-- 
Jakub Wilk

Re: [PATCH] man/man3/opendir.3: document that long file names result in ENAMETOOLONG

[Alejandro Colomar]

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Hi Collin, Jakub,

On Fri, Oct 17, 2025 at 10:45:53AM +0200, Jakub Wilk wrote:
> * Collin Funk <collin.funk1@gmail.com>, 2025-10-17 01:18:
> >    $ mkdir -p `python3 -c 'print("./" + "a/" * 32768)'`
> >    $ ./a.out `python3 -c 'print("./" + "a/" * 32768)'`
> >    File name too long

Thanks!  I've applied the patch.

> 
> Simpler reproducer:
> 
> $ ./a.out $(printf '%0999d')
> File name too long

And also thanks!  I've amended the commit message to use the simpler
reproducer.

I've also tweaked the source code for style.  I'll push to master
tomorrow.  (And probably, issue a new release too.)


Have a lovely night!
Alex

-- 
<https://www.alejandro-colomar.es>
Use port 80 (that is, <...:80/>).

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Re: [PATCH] man/man3/opendir.3: document that long file names result in ENAMETOOLONG

[Collin Funk]

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Alejandro Colomar <alx@kernel.org> writes:

> Hi Collin, Jakub,
>
> On Fri, Oct 17, 2025 at 10:45:53AM +0200, Jakub Wilk wrote:
>> * Collin Funk <collin.funk1@gmail.com>, 2025-10-17 01:18:
>> >    $ mkdir -p `python3 -c 'print("./" + "a/" * 32768)'`
>> >    $ ./a.out `python3 -c 'print("./" + "a/" * 32768)'`
>> >    File name too long
>
> Thanks!  I've applied the patch.
>
>> 
>> Simpler reproducer:
>> 
>> $ ./a.out $(printf '%0999d')
>> File name too long
>
> And also thanks!  I've amended the commit message to use the simpler
> reproducer.

Thanks! That is fine. My example was a longer than needed since I was
testing long path handling in Coreutils and wanted deep directory
entries.

Collin


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