HP-UX Reference (11i v2 07/12) - 7 Device (Special) Files, 9 General Information, Index (vol 10)

zero(7) zero(7)

NAME

zero - zero ﬁle

DESCRIPTION

/dev/zero is a zero special ﬁle. Reads from a zero special ﬁle always return characters whose value is

"0" (\0 characters).

Data written on a zero special ﬁle is discarded or ignored.

Seeks on a zero special ﬁle always succeed.

Private mmap()

of a zero special ﬁle is allowed (see mmap(2)). Shared mmap() is allowed but the

memory region can be shared only with descendants of the current process.

The

mmap() of /dev/zero is special in that it behaves as a

MAP_ANONYMOUS

object. Mapping

/dev/zero gives the calling program a block of zero-ﬁlled virtual memory of the size speciﬁed in the call

to mmap().

EXAMPLES

In the following example, the buffer "buf" is ﬁlled with "len" \0 characters.

fildes = open("/dev/zero",...)

read(fildes, buf, len)

In the following example, the process now has a range of "len" \0 characters at memory location "address":

fildes = open("/dev/zero",...)

address = mmap(0, len, PROT_READ | PROT_WRITE, MAP_PRIVATE, fildes,

any_offset)

FILES

/dev/zero