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RedHat 9 (Linux i386) - man page for sbrk (redhat section 2)

BRK(2)							     Linux Programmer's Manual							    BRK(2)

NAME
brk, sbrk - change data segment size
SYNOPSIS
#include <unistd.h> int brk(void *end_data_segment); void *sbrk(ptrdiff_t increment);
DESCRIPTION
brk 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 VALUE
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.
CONFORMING TO
BSD 4.3 brk and sbrk are not defined in the C Standard and are deliberately excluded from the POSIX.1 standard (see paragraphs B.1.1.1.3 and B.8.3.3).
SEE ALSO
execve(2), getrlimit(2), malloc(3) Linux 0.99.11 1993-07-21 BRK(2)