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1.\" $NetBSD: getdirentries.2,v 1.7 1995/10/12 15:40:50 jtc Exp $
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34.\" @(#)getdirentries.2 8.1 (Berkeley) 6/9/93
35.\"
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
48reads directory entries from the directory
49referenced by the file descriptor
50.Fa fd
51into the buffer pointed to by
52.Fa buf ,
53in a filesystem independent format.
54Up to
55.Fa nbytes
56of data will be transferred.
57.Fa Nbytes
58must be greater than or equal to the
59block size associated with the file,
60see
61.Xr stat 2 .
62Some filesystems may not support
63.Fn getdirentries
64with buffers smaller than this size.
65.Pp
66The data in the buffer is a series of
67.Em dirent
68structures each containing the following entries:
69.Bd -literal -offset indent
70unsigned long d_fileno;
71unsigned short d_reclen;
72unsigned short d_namlen;
73char d_name[MAXNAMELEN + 1]; /* see below */
74.Ed
75.Pp
76The
77.Fa d_fileno
78entry is a number which is unique for each
79distinct file in the filesystem.
80Files that are linked by hard links (see
81.Xr link 2 )
82have the same
83.Fa d_fileno .
84The
85.Fa d_reclen
86entry is the length, in bytes, of the directory record.
87The
88.Fa d_name
89entry contains a null terminated file name.
90The
91.Fa d_namlen
92entry specifies the length of the file name excluding the null byte.
93Thus the actual size of
94.Fa d_name
95may vary from 1 to
96.Dv MAXNAMELEN
97\&+ 1.
98.Pp
99Entries may be separated by extra space.
100The
101.Fa d_reclen
102entry may be used as an offset from the start of a
103.Fa dirent
104structure to the next structure, if any.
105.Pp
106The actual number of bytes transferred is returned.
107The current position pointer associated with
108.Fa fd
109is set to point to the next block of entries.
110The pointer may not advance by the number of bytes returned by
111.Fn getdirentries .
112A value of zero is returned when
113the end of the directory has been reached.
114.Pp
115.Fn Getdirentries
116writes the position of the block read into the location pointed to by
117.Fa basep .
118Alternatively, the current position pointer may be set and retrieved by
119.Xr lseek 2 .
120The current position pointer should only be set to a value returned by
121.Xr lseek 2 ,
122a value returned in the location pointed to by
123.Fa basep ,
124or zero.
125.Sh RETURN VALUES
126If successful, the number of bytes actually transferred is returned.
127Otherwise, -1 is returned and the global variable
128.Va errno
129is set to indicate the error.
130.Sh ERRORS
131.Fn Getdirentries
132will fail if:
133.Bl -tag -width Er
134.It Bq Er EBADF
135.Fa fd
136is not a valid file descriptor open for reading.
137.It Bq Er EFAULT
138Either
139.Fa buf
140or
141.Fa basep
142point outside the allocated address space.
143.It Bq Er EIO
144An
145.Tn I/O
146error 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
152The
153.Fn getdirentries
154function first appeared in 4.4BSD.