brk, sbrk - change data segment size
int brk(void *end_data_segment));
void *sbrk(ptrdiff_t increment));
brk sets the end of the data segment to the value specified
by end_data_segment. end_datasegment must be greater than
end of the text segment and it must be 16kB before the end
of the stack.
sbrk increments the program's data space by increment bytes.
sbrk isn't a system call, it is just a C library wrapper.
On success, brk returns zero, and sbrk returns a pointer to
the start of the new area. On error, -1 is returned, and
errno is set to ENOMEM.
brk and sbrk are not defined in the C Standard and are deli-
berately excluded from the POSIX.1 standard (see paragraphs
B.22.214.171.124 and B.8.3.3).
execve(2), getrlimit(2), malloc(3)