getdirentries(2) [freebsd man page]

GETDIRENTRIES(2)					      BSD System Calls Manual						  GETDIRENTRIES(2)

NAME

     getdirentries, getdents -- get directory entries in a file system independent format

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <sys/types.h>
     #include <dirent.h>

     int
     getdirentries(int fd, char *buf, int nbytes, long *basep);

     int
     getdents(int fd, char *buf, int nbytes);

DESCRIPTION

     The getdirentries() and getdents() system calls read directory entries from the directory referenced by the file descriptor fd into the buf-
     fer pointed to by buf, in a file system independent format.  Up to nbytes of data will be transferred.  The nbytes argument must be greater
     than or equal to the block size associated with the file, see stat(2).  Some file systems may not support these system calls with buffers
     smaller than this size.

     The data in the buffer is a series of dirent structures each containing the following entries:

	   uint32_t d_fileno;
	   uint16_t d_reclen;
	   uint8_t  d_type;
	   uint8_t  d_namlen;
	   char    d_name[MAXNAMELEN + 1]; /* see below */

     The d_fileno entry is a number which is unique for each distinct file in the file system.	Files that are linked by hard links (see link(2))
     have the same d_fileno.  The d_reclen entry is the length, in bytes, of the directory record.  The d_type entry is the type of the file
     pointed to by the directory record.  The file type values are defined in <sys/dirent.h>.  The d_name entry contains a null terminated file
     name.  The d_namlen entry specifies the length of the file name excluding the null byte.  Thus the actual size of d_name may vary from 1 to
     MAXNAMELEN + 1.

     Entries may be separated by extra space.  The d_reclen entry may be used as an offset from the start of a dirent structure to the next struc-
     ture, if any.

     The actual number of bytes transferred is returned.  The current position pointer associated with fd is set to point to the next block of
     entries.  The pointer may not advance by the number of bytes returned by getdirentries() or getdents().  A value of zero is returned when the
     end of the directory has been reached.

     The getdirentries() system call writes the position of the block read into the location pointed to by basep.  Alternatively, the current
     position pointer may be set and retrieved by lseek(2).  The current position pointer should only be set to a value returned by lseek(2), a
     value returned in the location pointed to by basep (getdirentries() only) or zero.

RETURN VALUES

     If successful, the number of bytes actually transferred is returned.  Otherwise, -1 is returned and the global variable errno is set to indi-
     cate the error.

ERRORS

     The getdirentries() system call will fail if:

     [EBADF]		The fd argument is not a valid file descriptor open for reading.

     [EFAULT]		Either buf or basep point outside the allocated address space.

     [EINVAL]		The file referenced by fd is not a directory, or nbytes is too small for returning a directory entry or block of entries,
			or the current position pointer is invalid.

     [EIO]		An I/O error occurred while reading from or writing to the file system.

SEE ALSO

     lseek(2), open(2)

HISTORY

     The getdirentries() system call first appeared in 4.4BSD.	The getdents() system call first appeared in FreeBSD 3.0.

BSD
								    May 3, 1995 							       BSD

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getdirentries(2) System Calls Manual getdirentries(2)

Name
getdirentries - gets directory entries in a generic directory format

Syntax
#include <sys/dir.h>

cc = getdirentries(fd, buf, nbytes, basep)
int cc, fd;
char *buf;
int nbytes;
long *basep;

Description
The system call puts directory entries from the directory referenced by the file descriptor fd into the buffer pointed to by buf, in a
generic directory format. Up to nbytes of data are transferred. The nbytes of data must be greater than or equal to the block size asso-
ciated with the file. For further information, see Sizes less than nbytes can cause errors on certain file systems.

The data returned in the buffer is a series of direct structures, each containing the following entries:
unsigned long d_ino;
unsigned short d_reclen;
unsigned short d_namlen;
char d_name[MAXNAMLEN + 1];

The d_ino entry is a number that is unique for each distinct file in the file system. Files that are linked by hard links have the same
d_ino . For further information, see The d_reclen entry is the length, in bytes, of the directory record. The d_namlen entry specifies
the length of the file name. The d_name entry contains a null-terminated file name. Thus, the actual size of d_name can vary from 2 to
MAXNAMLEN + 1.

The generic directory structures are not necessarily tightly packed. The d_reclen entry may be used as an offset from the beginning of a
direct structure to the next structure, if any.

Upon return, the actual number of bytes transferred is returned. The current position pointer associated with fd is set to point to the
next block of entries. The pointer is not necessarily incremented by the number of bytes returned by If the value returned is zero, the
end of the directory has been reached. The current position pointer may be set and retrieved by The system call writes the position of the
block read into the location pointed to by basep. It is not safe to set the current position pointer to any value other than a value pre-
viously returned by or a value previously returned in the location pointed to by basep or zero.

Return Values
If successful, the number of bytes actually transferred is returned. Otherwise, a -1 is returned and the global variable errno is set to
indicate the error.

Diagnostics
The system call fails under the following conditions:

EBADF The fd is not a valid file descriptor open for reading.

ENOTDIR The fd is not a directory.

EFAULT Either buf or basep points outside the allocated address space.

EIO While reading from or writing to the file system, an I/O error occurred.

EINTR A read from a slow device was interrupted by the delivery of a signal before any data arrived.

EPERM The user does not have read permission in the directory. The system call is not the suggested interface for reading direc-
tories. The and routines offer a standard interface. See the reference page for information on these routines.

See Also
close(2), link(2), lseek(2), open(2), stat(2), directory(3)

getdirentries(2)

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getdirentries(2) [freebsd man page]

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