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FreeBSD 11.0 - man page for bwrite (freebsd section 3)

BREAD(3)						   BSD Library Functions Manual 						  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); int berase(struct uufsd *disk, ufs2_daddr_t blockno, ufs2_daddr_t size);
DESCRIPTION
The bread(), bwrite() and berase() functions provide a block read, write and erase 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 current 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. The berase() function returns non-zero on error.
ERRORS
The function bread() may fail and set errno for any of the errors specified for the library functions ufs_disk_write(3) or pread(2). The function bwrite() may fail and set errno for any of the errors specified for the library function pwrite(2). The function berase() may fail and set errno for any of the errors specified for the library function ioctl(2). Additionally all three functions 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>
BSD
June 4, 2003 BSD