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 <sys/types.h>
  44 .Fd #include <sys/dirent.h>
  45 .Ft int
  46 .Fn getdirentries "int fd" "char *buf" "int nbytes" "long *basep"
  47 .Sh DESCRIPTION
  48 .Fn Getdirentries
  49 reads directory entries from the directory
  50 referenced by the file descriptor
  51 .Fa fd
  52 into the buffer pointed to by
  53 .Fa buf ,
  54 in a filesystem independent format.
  55 Up to
  56 .Fa nbytes
  57 of data will be transferred.
  58 .Fa Nbytes
  59 must be greater than or equal to the
  60 block size associated with the file,
  61 see
  62 .Xr stat 2 .
  63 Some filesystems may not support
  64 .Fn getdirentries
  65 with buffers smaller than this size.
  66 .Pp
  67 The data in the buffer is a series of
  68 .Em dirent
  69 structures each containing the following entries:
  70 .Bd -literal -offset indent
  71 u_int32_t       d_fileno;             /* file number of entry */
  72 u_int16_t       d_reclen;             /* length of this record */
  73 u_int8_t        d_type;               /* file type, see below */
  74 u_int8_t        d_namlen;             /* length of string in d_name */
  75 char            d_name[MAXNAMELEN + 1]; /* see below */
  76 .Ed
  77 .Pp
  78 The
  79 .Fa d_fileno
  80 entry is a number which is unique for each
  81 distinct file in the filesystem.
  82 Files that are linked by hard links (see
  83 .Xr link 2 )
  84 have the same
  85 .Fa d_fileno .
  86 Users of
  87 .Fn getdirentries
  88 should skip
  89 entries with
  90 .Fa d_fileno
  91 = 0, as such entries represent files which have been deleted but not yet removed from the directory entry.
  92 The
  93 .Fa d_reclen
  94 entry is the length, in bytes, of the directory record.
  95 The
  96 .Fa d_name
  97 entry contains a null terminated file name.
  98 The
  99 .Fa d_namlen
 100 entry specifies the length of the file name excluding the null byte.
 101 Thus the actual size of
 102 .Fa d_name
 103 may vary from 1 to
 104 .Dv MAXNAMELEN
 105 \&+ 1.
 106 .Fa d_type
 107 is a integer representing the type of the directory entry.  The following types are defined in
 108 .Aq sys/dirent.h :
 109 .Bd -literal -offset indent
 110 #define DT_UNKNOWN       0
 111 #define DT_FIFO          1
 112 #define DT_CHR           2
 113 #define DT_DIR           4
 114 #define DT_BLK           6
 115 #define DT_REG           8
 116 #define DT_LNK          10
 117 #define DT_SOCK         12
 118 #define DT_WHT          14
 119 .Ed
 120 .Pp
 121 Entries may be separated by extra space.
 122 The
 123 .Fa d_reclen
 124 entry may be used as an offset from the start of a
 125 .Fa dirent
 126 structure to the next structure, if any.
 127 .Pp
 128 The actual number of bytes transferred is returned.
 129 The current position pointer associated with
 130 .Fa fd
 131 is set to point to the next block of entries.
 132 The pointer may not advance by the number of bytes returned by
 133 .Fn getdirentries .
 134 A value of zero is returned when
 135 the end of the directory has been reached.
 136 .Pp
 137 .Fn Getdirentries
 138 writes the position of the block read into the location pointed to by
 139 .Fa basep .
 140 Alternatively, the current position pointer may be set and retrieved by
 141 .Xr lseek 2 .
 142 The current position pointer should only be set to a value returned by
 143 .Xr lseek 2 ,
 144 a value returned in the location pointed to by
 145 .Fa basep ,
 146 or zero.
 147 .Sh RETURN VALUES
 148 If successful, the number of bytes actually transferred is returned.
 149 Otherwise, -1 is returned and the global variable
 150 .Va errno
 151 is set to indicate the error.
 152 .Sh ERRORS
 153 .Fn Getdirentries
 154 will fail if:
 155 .Bl -tag -width Er
 156 .It Bq Er EBADF
 157 .Fa fd
 158 is not a valid file descriptor open for reading.
 159 .It Bq Er EFAULT
 160 Either
 161 .Fa buf
 162 or
 163 .Fa basep
 164 point outside the allocated address space.
 165 .It Bq Er EIO
 166 An
 167 .Tn I/O
 168 error occurred while reading from or writing to the file system.
 169 .El
 170 .Sh SEE ALSO
 171 .Xr open 2 ,
 172 .Xr lseek 2
 173 .Sh HISTORY
 174 The
 175 .Fn getdirentries
 176 function first appeared in 4.4BSD.