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>

       ssize_t
       getdirentries(int fd, char *buf, size_t nbytes, off_t *basep);

       ssize_t
       getdents(int fd, char *buf, size_t 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:

             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_off field returns a cookie which can be
       used with lseek(2) to position the directory descriptor to the next entry.  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), a value returned in the
       d_off field, or zero.

IMPLEMENTATION NOTES

       The d_off field is being used as a cookie to readdir for nfs servers.  These cookies can  be  cached  and
       allow to read directory entries at a specific offset on demand.

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.

       [EINTEGRITY]       Corrupted data was detected while reading from 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.

Debian                                           March 30, 2020                                 GETDIRENTRIES(2)