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.\" Author: Juli Mallett <jmallett@FreeBSD.org>
.\" Date: June 04, 2003
.\" Description:
.\" Manual page for libufs functions:
.\" bread(3)
.\" bwrite(3)
.\"
.\" This file is in the public domain.
.\"
.\" $FreeBSD$
.\"
.Dd June 4, 2003
.Dt BREAD 3
.Os
.Sh NAME
.Nm bread , bwrite
.Nd read and write blocks of a UFS filesystem
.Sh LIBRARY
.Lb libufs
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.In ufs/ufs/ufsmount.h
.In ufs/ufs/dinode.h
.In ufs/ffs/fs.h
.In libufs.h
.Ft ssize_t
.Fn bread "struct uufsd *disk" "ufs2_daddr_t blockno" "void *data" "size_t size"
.Ft ssize_t
.Fn bwrite "struct uufsd *disk" "ufs2_daddr_t blockno" "const void *data" "size_t size"
.Sh DESCRIPTION
The
.Fn bread
and
.Fn bwrite
functions provide a block read and write API for
.Xr libufs 3
consumers.
They operate on a userland UFS disk structure, and perform the read
and write at a given block address, which uses the current
.Fa d_bsize
value of the structure.
.Pp
The
.Fn bread
and
.Fn bwrite
functions return the amount read or written, or -1 in case of any error,
including short read.
.Sh ERRORS
The function
.Fn bread
may fail and set
.Va errno
for any of the errors specified for the library functions
.Xr ufs_disk_write 3
or
.Xr pread 2 .
Additionally, it may follow the
.Xr libufs 3
error methodologies in situations where the amount of data read
is not equal to the amount requested, or in case of device error.
.Pp
The function
.Fn bwrite
may fail and set
.Va errno
for any of the errors specified for the library function
.Xr pwrite 2 .
Additionally, it may follow the
.Xr libufs 3
error methodologies in situations where the amount of data written
is not equal to the amount requested, or in case of a device error.
.Sh SEE ALSO
.Xr libufs 3 ,
.Xr ufs_disk_write 3
.Sh HISTORY
These functions first appeared as part of
.Xr libufs 3
in
.Fx 5.0 .
.Sh AUTHORS
.An Juli Mallett Aq jmallett@FreeBSD.org
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