bsd/man/man2/getdirentries.2

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  34 .\"     @(#)getdirentries.2     8.1 (Berkeley) 6/9/93
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  36 .Dd June 9, 1993
  37 .Dt GETDIRENTRIES 2
  38 .Os
  39 .Sh NAME
  40 .Nm getdirentries
  41 .Nd "get directory entries in a filesystem independent format"
  42 .Sh SYNOPSIS
  43 .Fd #include <dirent.h>
  44 .Ft int
  45 .Fn getdirentries "int fd" "char *buf" "int nbytes" "long *basep"
  46 .Sh DESCRIPTION
  47 .Fn Getdirentries
  48 reads directory entries from the directory
  49 referenced by the file descriptor
  50 .Fa fd
  51 into the buffer pointed to by
  52 .Fa buf ,
  53 in a filesystem independent format.
  54 Up to
  55 .Fa nbytes
  56 of data will be transferred.
  57 .Fa Nbytes
  58 must be greater than or equal to the
  59 block size associated with the file,
  60 see
  61 .Xr stat 2 .
  62 Some filesystems may not support
  63 .Fn getdirentries
  64 with buffers smaller than this size.
  65 .Pp
  66 The data in the buffer is a series of
  67 .Em dirent
  68 structures each containing the following entries:
  69 .Bd -literal -offset indent
  70 unsigned long   d_fileno;
  71 unsigned short  d_reclen;
  72 unsigned short  d_namlen;
  73 char            d_name[MAXNAMELEN + 1]; /* see below */
  74 .Ed
  75 .Pp
  76 The
  77 .Fa d_fileno
  78 entry is a number which is unique for each
  79 distinct file in the filesystem.
  80 Files that are linked by hard links (see
  81 .Xr link 2 )
  82 have the same
  83 .Fa d_fileno .
  84 The
  85 .Fa d_reclen
  86 entry is the length, in bytes, of the directory record.
  87 The
  88 .Fa d_name
  89 entry contains a null terminated file name.
  90 The
  91 .Fa d_namlen
  92 entry specifies the length of the file name excluding the null byte.
  93 Thus the actual size of
  94 .Fa d_name
  95 may vary from 1 to
  96 .Dv MAXNAMELEN
  97 \&+ 1.
  98 .Pp
  99 Entries may be separated by extra space.
 100 The
 101 .Fa d_reclen
 102 entry may be used as an offset from the start of a
 103 .Fa dirent
 104 structure to the next structure, if any.
 105 .Pp
 106 The actual number of bytes transferred is returned.
 107 The current position pointer associated with
 108 .Fa fd
 109 is set to point to the next block of entries.
 110 The pointer may not advance by the number of bytes returned by
 111 .Fn getdirentries .
 112 A value of zero is returned when
 113 the end of the directory has been reached.
 114 .Pp
 115 .Fn Getdirentries
 116 writes the position of the block read into the location pointed to by
 117 .Fa basep .
 118 Alternatively, the current position pointer may be set and retrieved by
 119 .Xr lseek 2 .
 120 The current position pointer should only be set to a value returned by
 121 .Xr lseek 2 ,
 122 a value returned in the location pointed to by
 123 .Fa basep ,
 124 or zero.
 125 .Sh RETURN VALUES
 126 If successful, the number of bytes actually transferred is returned.
 127 Otherwise, -1 is returned and the global variable
 128 .Va errno
 129 is set to indicate the error.
 130 .Sh ERRORS
 131 .Fn Getdirentries
 132 will fail if:
 133 .Bl -tag -width Er
 134 .It Bq Er EBADF
 135 .Fa fd
 136 is not a valid file descriptor open for reading.
 137 .It Bq Er EFAULT
 138 Either
 139 .Fa buf
 140 or
 141 .Fa basep
 142 point outside the allocated address space.
 143 .It Bq Er EIO
 144 An
 145 .Tn I/O
 146 error occurred while reading from or writing to the file system.
 147 .El
 148 .Sh SEE ALSO
 149 .Xr open 2 ,
 150 .Xr lseek 2
 151 .Sh HISTORY
 152 The
 153 .Fn getdirentries
 154 function first appeared in 4.4BSD.