bwrite(3) [freebsd man page]

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

CGREAD(3)						   BSD Library Functions Manual 						 CGREAD(3)

NAME

     cgread, cgread1, cgwrite1 -- read/write cylinder groups of UFS disks

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>

     int
     cgread(struct uufsd *disk);

     int
     cgread1(struct uufsd *disk, int c);

     int
     cgwrite1(struct uufsd *disk, int c);

DESCRIPTION

     The cgread() and cgread1() functions provide cylinder group reads for libufs(3) consumers.  The cgread1() function reads from one cylinder
     group, specified by c into the d_cg field of a userland UFS disk structure.  It sets the d_lcg field to the cylinder group number c.

     The cgread() function operates on sequential cylinder groups.  Calling the cgread() function is equivalent to calling cgread1() with a cylin-
     der group specifier equivalent to the value of the current d_ccg field, and then incrementing the d_ccg field.

     The cgwrite1() function stores cylinder group specified by c from d_cg field of a userland UFS disk structure on disk.

RETURN VALUES

     Both functions return 0 if there are no more cylinder groups to read, 1 if there are more cylinder groups, and -1 on error.

ERRORS

     The function cgread() may fail and set errno for any of the errors specified for the library function bread(3).

     The function cgread1() has semantically identical failure conditions to those of cgread().

     The function cgwrite1() may fail and set errno for any of the errors specified for the library function bwrite(3).

SEE ALSO

     bread(3), bwrite(3), libufs(3)

HISTORY

     These functions first appeared as part of libufs(3) in FreeBSD 5.1.

AUTHORS

     Juli Mallett <jmallett@FreeBSD.org>

BSD
								   June 4, 2003 							       BSD