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  2009-10-02 "Linux" "Linux Programmer's Manual"
  28 .SH NAME
  29 getdents \- get directory entries
  30 .SH SYNOPSIS
  31 .nf
  32 .BI "int getdents(unsigned int " fd ", struct linux_dirent *" dirp ,
  33 .BI "             unsigned int " count );
  34 .fi
  35 .SH DESCRIPTION
  36 This is not the function you are interested in.
  37 Look at
  38 .BR readdir (3)
  39 for the POSIX conforming C library interface.
  40 This page documents the bare kernel system call interface.
  41 .PP
  42 The system call
  43 .BR getdents ()
  44 reads several
  45 .I linux_dirent
  46 structures from the directory
  47 referred to by the open file descriptor
  48 .I fd
  49 into the buffer pointed to by
  50 .IR dirp .
  51 The argument
  52 .I count
  53 is specifies the size of that buffer.
  54 .PP
  55 The
  56 .I linux_dirent
  57 structure is declared as follows:
  58 .PP
  59 .in +4n
  60 .nf
  61 struct linux_dirent {
  62     unsigned long  d_ino;     /* Inode number */
  63     unsigned long  d_off;     /* Offset to next \fIlinux_dirent\fP */
  64     unsigned short d_reclen;  /* Length of this \fIlinux_dirent\fP */
  65     char           d_name[];  /* Filename (null-terminated) */
  66                         /* length is actually (d_reclen \- 2 \-
  67                            offsetof(struct linux_dirent, d_name) */
  68     /*
  69     char           pad;       // Zero padding byte */
  70     char           d_type;    // File type (only since Linux 2.6.4;
  71                               // offset is (d_reclen \- 1))
  72     */
  73
  74 }
  75 .fi
  76 .in
  77 .PP
  78 .I d_ino
  79 is an inode number.
  80 .I d_off
  81 is the distance from the start of the directory to the start of the next
  82 .IR linux_dirent .
  83 .I d_reclen
  84 is the size of this entire
  85 .IR linux_dirent .
  86 .I d_name
  87 is a null-terminated filename.
  88
  89 .I d_type
  90 is a byte at the end of the structure that indicates the file type.
  91 It contains one of the following values (defined in
  92 .IR <dirent.h> ):
  93 .TP 12
  94 .B DT_BLK
  95 This is a block device.
  96 .TP
  97 .B DT_CHR
  98 This is a character device.
  99 .TP
 100 .B DT_DIR
 101 This is a directory.
 102 .TP
 103 .B DT_FIFO
 104 This is a named pipe (FIFO).
 105 .TP
 106 .B DT_LNK
 107 This is a symbolic link.
 108 .TP
 109 .B DT_REG
 110 This is a regular file.
 111 .TP
 112 .B DT_SOCK
 113 This is a Unix domain socket.
 114 .TP
 115 .B DT_UNKNOWN
 116 The file type is unknown.
 117 .PP
 118 Curently,
 119 .\" kernel 2.6.27
 120 only ext2, ext3, and ext4 support returning the file type in
 121 .IR d_type .
 122 On other file systems,
 123 this field is always set to
 124 .BR DT_UNKNOWN .
 125 .SH "RETURN VALUE"
 126 On success, the number of bytes read is returned.
 127 On end of directory, 0 is returned.
 128 On error, \-1 is returned, and
 129 .I errno
 130 is set appropriately.
 131 .SH ERRORS
 132 .TP
 133 .B EBADF
 134 Invalid file descriptor
 135 .IR fd .
 136 .TP
 137 .B EFAULT
 138 Argument points outside the calling process's address space.
 139 .TP
 140 .B EINVAL
 141 Result buffer is too small.
 142 .TP
 143 .B ENOENT
 144 No such directory.
 145 .TP
 146 .B ENOTDIR
 147 File descriptor does not refer to a directory.
 148 .SH "CONFORMING TO"
 149 SVr4.
 150 .\" SVr4 documents additional ENOLINK, EIO error conditions.
 151 .SH NOTES
 152 Glibc does not provide a wrapper for this system call; call it using
 153 .BR syscall (2).
 154 You will need to define the
 155 .I linux_dirent
 156 structure yourself.
 157
 158 This call supersedes
 159 .BR readdir (2).
 160 .SH "SEE ALSO"
 161 .BR readdir (2),
 162 .BR readdir (3)