|BRK(2)||Linux Programmer's Manual||BRK(2)|
NAME¶brk, sbrk - change data segment size
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
- Since glibc 2.12:
_BSD_SOURCE || _SVID_SOURCE || (_XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) && !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
Before glibc 2.12:
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
DESCRIPTION¶brk() and sbrk() change the location of the program break, which defines the end of the process's data segment (i.e., the program break is the first location after the end of the uninitialized data segment). Increasing the program break has the effect of allocating memory to the process; decreasing the break deallocates memory.
RETURN VALUE¶On success, brk() returns zero. On error, -1 is returned, and errno is set to ENOMEM. (But see Linux Notes below.)
CONFORMING TO¶4.3BSD; SUSv1, marked LEGACY in SUSv2, removed in POSIX.1-2001.
NOTES¶Avoid using brk() and sbrk(): the malloc(3) memory allocation package is the portable and comfortable way of allocating memory.
Linux Notes¶The return value described above for brk() is the behavior provided by the glibc wrapper function for the Linux brk() system call. (On most other implementations, the return value from brk() is the same; this return value was also specified in SUSv2.) However, the actual Linux system call returns the new program break on success. On failure, the system call returns the current break. The glibc wrapper function does some work (i.e., checks whether the new break is less than addr) to provide the 0 and -1 return values described above.
SEE ALSO¶execve(2), getrlimit(2), end(3), malloc(3)
COLOPHON¶This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.