man2/getdents.2

   1 .\" Copyright (C) 1995 Andries Brouwer (aeb@cwi.nl)
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  22 .\"
  23 .\" Written 11 June 1995 by Andries Brouwer <aeb@cwi.nl>
  24 .\" Modified 22 July 1995 by Michael Chastain <mec@duracef.shout.net>:
  25 .\"   Derived from 'readdir.2'.
  26 .\" Modified Tue Oct 22 08:11:14 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
  27 .TH GETDENTS 2  2009-09-29 "Linux" "Linux Programmer's Manual"
  28 .SH NAME
  29 getdents \- get directory entries
  30 .SH SYNOPSIS
  31 .nf
  32 .B #include <unistd.h>
  33 .B #include <linux/types.h>
  34 .B #include <linux/dirent.h>
  35 .B #include <linux/unistd.h>
  36 .B #include <errno.h>
  37
  38 .BI "int getdents(unsigned int " fd ", struct dirent *" dirp ,
  39 .BI "             unsigned int " count );
  40 .fi
  41 .SH DESCRIPTION
  42 This is not the function you are interested in.
  43 Look at
  44 .BR readdir (3)
  45 for the POSIX conforming C library interface.
  46 This page documents the bare kernel system call interface.
  47 .PP
  48 The system call
  49 .BR getdents ()
  50 reads several
  51 .I dirent
  52 structures from the directory
  53 referred to by the open file descriptor
  54 .I fd
  55 into the buffer pointed to by
  56 .IR dirp .
  57 The argument
  58 .I count
  59 is the size of the memory area.
  60 .PP
  61 The
  62 .I dirent
  63 structure is declared as follows:
  64 .PP
  65 .in +4n
  66 .nf
  67 struct linux_dirent {
  68     unsigned long  d_ino;     /* Inode number */
  69     unsigned long  d_off;     /* Offset to next \fIdirent\fP */
  70     unsigned short d_reclen;  /* Length of this \fIdirent\fP */
  71     char           d_name []; /* Filename (null-terminated) */
  72                         /* length is actually (d_reclen \- 2 \-
  73                            offsetof(struct linux_dirent, d_name) */
  74     char           pad;       /* Zero padding byte */
  75     char           d_type;    /* File type (only since Linux 2.6.4;
  76                                  offset is (d_reclen \- 1)) */
  77
  78 }
  79 .fi
  80 .in
  81 .PP
  82 .I d_ino
  83 is an inode number.
  84 .I d_off
  85 is the distance from the start of the directory to the start of the next
  86 .IR dirent .
  87 .I d_reclen
  88 is the size of this entire
  89 .IR dirent .
  90 .I d_name
  91 is a null-terminated filename.
  92
  93 .I d_type
  94 is a byte at the end of the structure that indicates the file type.
  95 It contains one of the following values:
  96 .TP 12
  97 .B DT_BLK
  98 This is a block device.
  99 .TP
 100 .B DT_CHR
 101 This is a character device.
 102 .TP
 103 .B DT_DIR
 104 This is a directory.
 105 .TP
 106 .B DT_FIFO
 107 This is a named pipe (FIFO).
 108 .TP
 109 .B DT_LNK
 110 This is a symbolic link.
 111 .TP
 112 .B DT_REG
 113 This is a regular file.
 114 .TP
 115 .B DT_SOCK
 116 This is a Unix domain socket.
 117 .TP
 118 .B DT_UNKNOWN
 119 The file type is unknown.
 120 .PP
 121 Curently,
 122 .\" kernel 2.6.27
 123 only ext2, ext3, and ext4 support returning the file type in
 124 .IR d_type .
 125 On other file systems,
 126 this field is always set to
 127 .BR DT_UNKNOWN .
 128 .SH "RETURN VALUE"
 129 On success, the number of bytes read is returned.
 130 On end of directory, 0 is returned.
 131 On error, \-1 is returned, and
 132 .I errno
 133 is set appropriately.
 134 .SH ERRORS
 135 .TP
 136 .B EBADF
 137 Invalid file descriptor
 138 .IR fd .
 139 .TP
 140 .B EFAULT
 141 Argument points outside the calling process's address space.
 142 .TP
 143 .B EINVAL
 144 Result buffer is too small.
 145 .TP
 146 .B ENOENT
 147 No such directory.
 148 .TP
 149 .B ENOTDIR
 150 File descriptor does not refer to a directory.
 151 .SH "CONFORMING TO"
 152 SVr4.
 153 .\" SVr4 documents additional ENOLINK, EIO error conditions.
 154 .SH NOTES
 155 Glibc does not provide a wrapper for this system call; call it using
 156 .BR syscall (2).
 157
 158 This call supersedes
 159 .BR readdir (2).
 160 .SH "SEE ALSO"
 161 .BR readdir (2),
 162 .BR readdir (3)