CGREAD(3) BSD Library Functions Manual CGREAD(3)NAME
cgread, cgread1, cgwrite1 — read/write cylinder groups of UFS disks
cgread(struct uufsd *disk);
cgread1(struct uufsd *disk, int c);
cgwrite1(struct uufsd *disk, int c);
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 struc‐
ture. 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 cylinder
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.
Both functions return 0 if there are no more cylinder groups to read, 1
if there are more cylinder groups, and -1 on error.
The function cgread() may fail and set errno for any of the errors speci‐
fied 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 ALSObread(3), bwrite(3), libufs(3)HISTORY
These functions first appeared as part of libufs(3) in FreeBSD 5.1.
Juli Mallett ⟨jmallett@FreeBSD.org⟩
BSD June 4, 2003 BSD