sbrk(2) -- Linux man page
NAMEbrk, sbrk - change data segment size
int brk(void *end_data_segment);
DESCRIPTIONbrk sets the end of the data segment to the value specified by end_data_segment, when that value is reasonable, the system does have enough memory and the process does not exceed its max data size (see setrlimit(2)).
sbrk increments the program's data space by increment bytes. sbrk isn't a system call, it is just a C library wrapper. Calling sbrk with an increment of 0 can be used to find the current location of the program break.
RETURN VALUEOn 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.
CONFORMING TOBSD 4.3
NOTESVarious systems use various types for the parameter of sbrk(). Common are int, ssize_t, ptrdiff_t, intptr_t. XPGv6 obsoletes this function.
SEE ALSOexecve(2), getrlimit(2), malloc(3)