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 buffer
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:
u_int32_t d_fileno;
u_int16_t d_reclen;
u_int8_t d_type;
u_int8_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 structure,
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
indicate 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.