harvey/sys/man/2/dirread

.TH DIRREAD 2
.SH NAME
dirread, dirreadall \- read directory
.SH SYNOPSIS
.B #include <u.h>
.br
.B #include <libc.h>
.PP
.B
long dirread(int fd, Dir **buf)
.PP
.B
long dirreadall(int fd, Dir **buf)
.PP
.B
#define	STATMAX	65535U
.PP
.B
#define	DIRMAX	(sizeof(Dir)+STATMAX)
.SH DESCRIPTION
The data returned by a
.IR read (2)
on a directory is a set of complete directory entries
in a machine-independent format, exactly equivalent to
the result of a
.IR stat (2)
on each file or subdirectory in the directory.
.I Dirread
decodes the directory entries into a machine-dependent form.
It reads from
.IR fd
and unpacks the data into an array of
.B Dir
structures
whose address is returned in
.B *buf
(see
.IR stat (2)
for the layout of a
.BR Dir ).
The array is allocated with
.IR malloc (2)
each time
.I dirread
is called.
.PP
.I Dirreadall
is like
.IR dirread ,
but reads in the entire directory; by contrast,
.I dirread
steps through a directory one
.IR read (2)
at a time.
.PP
Directory entries have variable length.
A successful
.I read
of a directory always returns an integral number of complete directory entries;
.I dirread
always returns complete
.B Dir
structures.
See
.IR read (5)
for more information.
.PP
The constant
.B STATMAX
is the maximum size that a directory entry can occupy.
The constant
.B DIRMAX
is an upper limit on the size necessary to hold a
.B Dir
structure and all the associated data.
.PP
.I Dirread
and
.I dirreadall
return the number of
.B Dir
structures filled in
.BR buf .
The file offset is advanced by the number of bytes actually read.
.SH SOURCE
.B /sys/src/libc/9sys/dirread.c
.SH SEE ALSO
.IR intro (2),
.IR open (2),
.IR read (2)
.SH DIAGNOSTICS
.I Dirread
and
.I Dirreadall
return zero for end of file and a negative value for error.
In either case,
.B *buf
is set to
.B nil
so the pointer can always be freed with impunity.
.PP
These functions set
.IR errstr .