Provided by: manpages-dev_2.77-1_all
brk, sbrk - change data segment size
int brk(void *end_data_segment);
void *sbrk(intptr_t increment);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
brk(), sbrk(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500
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
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
On success, brk() returns zero. On error, -1 is returned, and errno is
set to ENOMEM. (But see Linux Notes below.)
On success, sbrk() returns a pointer to the start of the new area. On
error, -1 is returned, and errno is set to ENOMEM.
4.3BSD; SUSv1, marked LEGACY in SUSv2, removed in POSIX.1-2001.
brk() and sbrk() are not defined in the C Standard and are deliberately
excluded from the POSIX.1 standard (see paragraphs B.126.96.36.199 and
Various systems use various types for the parameter of sbrk(). Common
are int, ssize_t, ptrdiff_t, intptr_t.
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.)
However, the actual Linux system call returns the new program break on
success. On failure, the system call returns the current break (thus
for example, the call brk(0) can be used to obtain the current break).
The glibc wrapper function does some work to provide the 0 and -1
return values described above.
On Linux, sbrk() is implemented as a library function that uses the
brk() system call, and does some internal bookkeeping so that it can
return the old break value.
execve(2), getrlimit(2), malloc(3)
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