NAME
getdirentries,
getdents —
get directory entries in a file system
independent format
LIBRARY
library “libc”
SYNOPSIS
#include
<sys/types.h>
#include <dirent.h>
ssize_t
getdirentries(int
fd, char *buf,
size_t nbytes,
off_t *basep);
ssize_t
getdents(int
fd, char *buf,
size_t nbytes);
DESCRIPTION
Thegetdirentries()
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:
ino_t d_fileno; off_t d_off; uint16_t d_reclen; uint8_t d_type; uint16_t d_namlen; char d_name[MAXNAMLEN + 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
MAXNAMLEN + 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.
If the basep pointer
value is non-NULL , 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 non-NULL 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
HISTORY
The getdirentries() system call first
appeared in 4.4BSD. The
getdents() system call first appeared in
FreeBSD 3.0.