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 speci
fied 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
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
deliberately excluded from the POSIX.1 standard (see para
graphs B.18.104.22.168 and B.8.3.3).
execve(2), getrlimit(2), malloc(3)