4.3BSD-UWisc/man/cat2/getrlimit.2
GETRLIMIT(2) UNIX Programmer's Manual GETRLIMIT(2)
NAME
getrlimit, setrlimit - control maximum system resource con-
sumption
SYNOPSIS
#include <sys/time.h>
#include <sys/resource.h>
getrlimit(resource, rlp)
int resource;
struct rlimit *rlp;
setrlimit(resource, rlp)
int resource;
struct rlimit *rlp;
DESCRIPTION
Limits on the consumption of system resources by the current
process and each process it creates may be obtained with the
_g_e_t_r_l_i_m_i_t call, and set with the _s_e_t_r_l_i_m_i_t call.
The _r_e_s_o_u_r_c_e parameter is one of the following:
RLIMIT_CPU the maximum amount of cpu time (in seconds)
to be used by each process.
RLIMIT_FSIZE the largest size, in bytes, of any single
file that may be created.
RLIMIT_DATA the maximum size, in bytes, of the data
segment for a process; this defines how far
a program may extend its break with the
_s_b_r_k(2) system call.
RLIMIT_STACK the maximum size, in bytes, of the stack
segment for a process; this defines how far
a program's stack segment may be extended.
Stack extension is performed automatically
by the system.
RLIMIT_CORE the largest size, in bytes, of a _c_o_r_e file
that may be created.
RLIMIT_RSS the maximum size, in bytes, to which a
process's resident set size may grow. This
imposes a limit on the amount of physical
memory to be given to a process; if memory
is tight, the system will prefer to take
memory from processes that are exceeding
their declared resident set size.
Printed 12/27/86 May 13, 1986 1
GETRLIMIT(2) UNIX Programmer's Manual GETRLIMIT(2)
A resource limit is specified as a soft limit and a hard
limit. When a soft limit is exceeded a process may receive
a signal (for example, if the cpu time is exceeded), but it
will be allowed to continue execution until it reaches the
hard limit (or modifies its resource limit). The _r_l_i_m_i_t
structure is used to specify the hard and soft limits on a
resource,
struct rlimit {
int rlim_cur; /* current (soft) limit */
int rlim_max; /* hard limit */
};
Only the super-user may raise the maximum limits. Other
users may only alter _r_l_i_m__c_u_r within the range from 0 to
_r_l_i_m__m_a_x or (irreversibly) lower _r_l_i_m__m_a_x.
An "infinite" value for a limit is defined as RLIM_INFINITY
(0x7fffffff).
Because this information is stored in the per-process infor-
mation, this system call must be executed directly by the
shell if it is to affect all future processes created by the
shell; _l_i_m_i_t is thus a built-in command to _c_s_h(1).
The system refuses to extend the data or stack space when
the limits would be exceeded in the normal way: a _b_r_e_a_k call
fails if the data space limit is reached. When the stack
limit is reached, the process receives a segmentation fault
(SIGSEGV); if this signal is not caught by a handler using
the signal stack, this signal will kill the process.
A file I/O operation that would create a file that is too
large will cause a signal SIGXFSZ to be generated; this nor-
mally terminates the process, but may be caught. When the
soft cpu time limit is exceeded, a signal SIGXCPU is sent to
the offending process.
RETURN VALUE
A 0 return value indicates that the call succeeded, changing
or returning the resource limit. A return value of -1
indicates that an error occurred, and an error code is
stored in the global location _e_r_r_n_o.
ERRORS
The possible errors are:
[EFAULT] The address specified for _r_l_p is invalid.
[EPERM] The limit specified to _s_e_t_r_l_i_m_i_t would have
raised the maximum limit value, and the
caller is not the super-user.
Printed 12/27/86 May 13, 1986 2
GETRLIMIT(2) UNIX Programmer's Manual GETRLIMIT(2)
SEE ALSO
csh(1), quota(2), sigvec(2), sigstack(2)
BUGS
There should be _l_i_m_i_t and _u_n_l_i_m_i_t commands in _s_h(1) as well
as in _c_s_h.
Printed 12/27/86 May 13, 1986 3