/dev/zero

From Wikipedia, the free encyclopedia

In Unix-like operating systems, /dev/zero is a special file that provides as many null characters (ASCII NUL, 0x00; not ASCII character "digit zero", "0", 0x30) as are read from it. One of the typical uses is to provide a character stream for overwriting information. Another might be to generate a clean file of a certain size. Using mmap to map /dev/zero to the virtual address space is the BSD way of implementing shared memory.

# Destroy data on a partition
dd if=/dev/zero of=/dev/hda8

# Create a (1MiB) file filled with zeroes called 'foobar'
dd if=/dev/zero of=foobar count=1024 bs=1024

Like /dev/null, /dev/zero acts as a source and sink for data. All writes to /dev/zero succeed with no other effects (the same as for /dev/null, although /dev/null is the more commonly used data sink); all reads on /dev/zero return as many NULs as characters requested.