NAME
zero — /dev/zero special 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.
When
/dev/zero
is memory mapped by calling
mmap(),
the associated memory object behaves as a
MAP_ANONYMOUS
object.
It is initialized to all zeros.
Writes to the object
modify the contents of the object which are observed by
subsequent reads to this object.
Both
MAP_SHARED
and
MAP_PRIVATE
mmap()
are allowed.
When it is mapped shared, the memory object can be
shared only with the descendants of the current
process.
Modifications made to the
MAP_SHARED
object are visible only to the process and its
descendants.
When it is mapped private, any modifications done
after
fork()
are visible only to the process.
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)
Printable version
