struct dirent variances Post: 302176181

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Top Forums Programming struct dirent variances Post 302176181 by odys on Monday 17th of March 2008 04:48:55 PM

03-17-2008

Registered User

struct dirent variances

Hello,

Recently I need to create a filesystem related code.
I noticed lot of inconsistent documentation regarding
struct dirent:

1. 'd_namlen' field
info libc in chapter ''File System Interface"
specifies 'd_namlen' field as length of 'd_name' string.
When compiling under Linux (and GNU libc obviously)
'd_namlen' is missing.

2. 'd_reclen'
this field is documented as "length of d_name" in readdir(2) whereas in '/usr/include/dirent.h' it is described as 'size of entire directory entry'. In 'info libc' 'd_reclen' is mentioned but not really described at all.

3. 'd_off' field
in readdir(2) this is offset to current dirent [from start of the directory], but again in '/usr/include/dirent.h' this is "offset of next directory entry".

I understand that only 'd_name' is really portable and it is enough for my purposes.
But could anybody explain above? In my opinion some of inconsistencies from 2. and 3. are due to readir(2)
possibly deals with kernel 'struct dirent' which can be independent of libc one.

Regards,
Miroslaw

Regards.

odys

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LEARN ABOUT SUNOS

dirent.h

dirent.h(3HEAD) 						      Headers							   dirent.h(3HEAD)

NAME

       dirent.h, dirent - format of directory entries

SYNOPSIS

       #include <dirent.h>

DESCRIPTION

       The internal format of directories is unspecified. The <dirent.h> header defines the following type:

       DIR	       A type representing a directory stream.

       The header also defines the structure dirent, which includes the following members:

       ino_t d_ino	  /* file serial number */
       char  d_name[]	  /* name of entry */

       The type ino_t is defined as described in <sys/types.h>. See types(3HEAD).

       The character array d_name is of unspecified size, but the number of bytes preceding the terminating null byte must not exceed {NAME_MAX}.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       closedir(3C), opendir(3C), readdir(3C), rewinddir(3C), seekdir(3C), telldir(3C), types.h(3HEAD), attributes(5), standards(5)

SunOS 5.10							    10 Sep 2004 						   dirent.h(3HEAD)

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