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brk(2)			      System Calls Manual			brk(2)

NAME
       brk, sbrk - change data segment space allocation

SYNOPSIS
DESCRIPTION
       and  are	 used  to change dynamically the amount	of space allocated for
       the calling process's data segment; see exec(2).	 The change is made by
       resetting  the  process's  break	 value	and allocating the appropriate
       amount of space.	 The break value is the	address	of the first  location
       beyond  the end of the data segment.  The amount	of allocated space in-
       creases as the break value increases.  The newly	allocated space	is set
       to zero.

       sets  the  break	value to endds and changes the allocated space accord-
       ingly.

       adds incr bytes to the break value and changes the allocated space  ac-
       cordingly.  incr	can be negative, in which case the amount of allocated
       space is	decreased.

ERRORS
       and fail	without	making any change in the allocated  space  if  one  or
       more of the following are true:

       [ENOMEM]	      Such a change would result in more space being allocated
		      than  is	allowed	 by  a	system-imposed	maximum	  (see
		      ulimit(2)).

       [ENOMEM]	      Such  a  change would cause a conflict between addresses
		      in the data segment and any attached shared memory  seg-
		      ment (see	shmop(2)).

       [ENOMEM]	      Such  a  change would be impossible as there is insuffi-
		      cient swap space available.

       [EINVAL]	      Such a change will result	in crossing  the  boundary  to
		      uninitialized  data  in  the calling process's data seg-
		      ment.

WARNINGS
       The pointer returned by is not necessarily  word-aligned.   Loading  or
       storing words through this pointer could	cause word alignment problems.

       Be  very	 careful when using either or in conjunction with calls	to the
       malloc(3C) library routines.  There is only one	program	 data  segment
       from  which all three of	these routines allocate	and deallocate program
       data memory.

RETURN VALUE
       Upon successful completion, returns a value of 0. Otherwise, a value of
       -1 is returned and is set to indicate the error.

       Upon  successful	completion, returns the	old break value. Otherwise, is
       returned	and is set to indicate the error. The symbol is	defined	in the
       header No successful return from	will return the	value

AUTHOR
       and were	developed by AT&T and HP.

SEE ALSO
       exec(2),	shmop(2), ulimit(2), end(3C), malloc(3C).

STANDARDS CONFORMANCE
									brk(2)

NAME | SYNOPSIS | DESCRIPTION | ERRORS | WARNINGS | RETURN VALUE | AUTHOR | SEE ALSO | STANDARDS CONFORMANCE

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