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bread(3)

NAME

     bread, bwrite -- read and write blocks of a UFS file system

LIBRARY

     UFS File System Access Library (libufs, -lufs)

SYNOPSIS

     #include <sys/param.h>
     #include <sys/mount.h>
     #include <ufs/ufs/ufsmount.h>
     #include <ufs/ufs/dinode.h>
     #include <ufs/ffs/fs.h>
     #include <libufs.h>

     ssize_t
     bread(struct uufsd *disk, ufs2_daddr_t blockno, void *data, size_t size);

     ssize_t
     bwrite(struct uufsd *disk, ufs2_daddr_t blockno, const void *data,
	 size_t size);

DESCRIPTION

     The bread() and bwrite() functions provide a block read and write API for
     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 cur-
     rent d_bsize value of the structure.

RETURN VALUES

     The bread() and bwrite() functions return the amount read or written, or
     -1 in case of any error, including short read.

ERRORS

     The function bread() may fail and set errno for any of the errors speci-
     fied for the library functions ufs_disk_write(3) or pread(2).  Addition-
     ally, it may follow the 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.

     The function bwrite() may fail and set errno for any of the errors speci-
     fied for the library function pwrite(2).  Additionally, it may follow the
     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.

SEE ALSO

     libufs(3), ufs_disk_write(3)

HISTORY

     These functions first appeared as part of libufs(3) in FreeBSD 5.0.

AUTHORS

     Juli Mallett <jmallett@FreeBSD.org>

FreeBSD 5.4			 June 4, 2003			   FreeBSD 5.4

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