brk和sbrk之间的区别

int brk(void *addr);

brk() sets the end of the data segment to the value specified by
addr,when that value is reasonable,the system has enough memory,
and the process does not exceed its maximum data size.

On success,brk() returns zero. On error,-1 is returned,and errno
is set to ENOMEM.

void *sbrk(intptr_t increment);

sbrk() increments the program’s data space by increment bytes.
Calling sbrk() with an increment of 0 can be used to find the current
location of the program break.

On success,sbrk() returns the previous program break. (If the break
was increased,then this value is a pointer to the start of the newly
allocated memory). On error,(void *) -1 is returned,and errno is
set to ENOMEM.

From linux manual page