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 .
