brk(2) — sys5



BRK(2)          DOMAIN/IX Reference Manual (SYS5)          BRK(2)



NAME
     brk, sbrk - change amount of memory available

USAGE
     int brk (endds)
     char *endds;

     char *sbrk (incr)
     int incr;

DESCRIPTION
     These calls extend the amount of memory available to a pro-
     gram, beyond what was allocated when the program was com-
     piled.  The break value is the address of the first location
     beyond the end of available memory; the amount of allocated
     space increases as the break value increases.  Brk and sbrk
     are used to change the break value while the process is run-
     ning.  The address of the newly allocated space is set to
     zero.

     Brk sets the break value to endds.

     Sbrk adds incr bytes to the break value.  Incr can be nega-
     tive, in which case the amount of allocated space is
     decreased.

RETURN VALUE
     Brk returns zero if the break was set; sbrk returns the old
     break value, if the call was successful.  Otherwise, the
     calls return -1 and set errno to indicate the error.

ERRORS
     Brk and sbrk will fail without making any changes if one or
     more of the following is true:

     [ENOMEM]       The change would result in more space being
                    allocated than a system-imposed maximum
                    allows (see set_sbrk_size(2)).

                    The change would result in the break value
                    being greater than or equal to the start
                    address of any attached shared memory segment
                    (see shmop(2)).

RELATED INFORMATION
     exec(2), shmop(2), ulimit(2), set_sbrk_size(2)









Printed 5/10/85                                             BRK-1
Museum
