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System Calls getrlimit(2)
NAME
getrlimit, setrlimit - control maximum system resource con-
sumption
SYNOPSIS
#include <sys/resource.h>
int getrlimit(int resource, struct rlimit *rlp);
int setrlimit(int resource, const struct rlimit *rlp);
DESCRIPTION
Limits on the consumption of a variety of system resources
by a process and each process it creates may be obtained
with the getrlimit() and set with setrlimit() functions.
Each call to either getrlimit() or setrlimit() identifies a
specific resource to be operated upon as well as a resource
limit. A resource limit is a pair of values: one specifying
the current (soft) limit, the other a maximum (hard) limit.
Soft limits may be changed by a process to any value that is
less than or equal to the hard limit. A process may
(irreversibly) lower its hard limit to any value that is
greater than or equal to the soft limit. Only a process with
{PRIV_SYS_RESOURCE} asserted in the effective set can raise
a hard limit. Both hard and soft limits can be changed in a
single call to setrlimit() subject to the constraints
described above. Limits may have an "infinite" value of
RLIM_INFINITY. The rlp argument is a pointer to struct
rlimit that includes the following members:
rlim_t rlim_cur; /* current (soft) limit */
rlim_t rlim_max; /* hard limit */
The type rlim_t is an arithmetic data type to which objects
of type int, size_t, and off_t can be cast without loss of
information.
The possible resources, their descriptions, and the actions
taken when the current limit is exceeded are summarized as
follows:
RLIMIT_CORE The maximum size of a core file in bytes
that may be created by a process. A limit of
0 will prevent the creation of a core file.
The writing of a core file will terminate at
this size.
SunOS 5.10 Last change: 21 Aug 2006 1
System Calls getrlimit(2)
RLIMIT_CPU The maximum amount of CPU time in seconds
used by a process. This is a soft limit
only. The SIGXCPU signal is sent to the
process. If the process is holding or ignor-
ing SIGXCPU, the behavior is scheduling
class defined.
RLIMIT_DATA The maximum size of a process's heap in
bytes. The brk(2) function will fail with
errno set to ENOMEM.
RLIMIT_FSIZE The maximum size of a file in bytes that may
be created by a process. A limit of 0 will
prevent the creation of a file. The SIGXFSZ
signal is sent to the process. If the pro-
cess is holding or ignoring SIGXFSZ, con-
tinued attempts to increase the size of a
file beyond the limit will fail with errno
set to EFBIG.
RLIMIT_NOFILE One more than the maximum value that the
system may assign to a newly created
descriptor. This limit constrains the number
of file descriptors that a process may
create.
RLIMIT_STACK The maximum size of a process's stack in
bytes. The system will not automatically
grow the stack beyond this limit.
Within a process, setrlimit() will increase
the limit on the size of your stack, but
will not move current memory segments to
allow for that growth. To guarantee that the
process stack can grow to the limit, the
limit must be altered prior to the execution
of the process in which the new stack size
is to be used.
Within a multithreaded process, setrlimit()
has no impact on the stack size limit for
the calling thread if the calling thread is
not the main thread. A call to setrlimit()
for RLIMIT_STACK impacts only the main
SunOS 5.10 Last change: 21 Aug 2006 2
System Calls getrlimit(2)
thread's stack, and should be made only from
the main thread, if at all.
The SIGSEGV signal is sent to the process.
If the process is holding or ignoring SIG-
SEGV, or is catching SIGSEGV and has not
made arrangements to use an alternate stack
(see sigaltstack(2)), the disposition of
SIGSEGV will be set to SIG_DFL before it is
sent.
RLIMIT_VMEM The maximum size of a process's mapped
address space in bytes. If this limit is
exceeded, the brk(2) and mmap(2) functions
will fail with errno set to ENOMEM. In
addition, the automatic stack growth will
fail with the effects outlined above.
RLIMIT_AS This is the maximum size of a process's
total available memory, in bytes. If this
limit is exceeded, the brk(2), malloc(3C),
mmap(2) and sbrk(2) functions will fail with
errno set to ENOMEM. In addition, the
automatic stack growth will fail with the
effects outlined above.
Because limit information is stored in the per-process
information, the shell builtin ulimit command must directly
execute this system call if it is to affect all future
processes created by the shell.
The value of the current limit of the following resources
affect these implementation defined parameters:
Limit Implementation Defined Constant
RLIMIT_FSIZE FCHR_MAX
RLIMIT_NOFILE OPEN_MAX
When using the getrlimit() function, if a resource limit can
be represented correctly in an object of type rlim_t, then
its representation is returned; otherwise, if the value of
the resource limit is equal to that of the corresponding
saved hard limit, the value returned is RLIM_SAVED_MAX; oth-
erwise the value returned is RLIM_SAVED_CUR.
SunOS 5.10 Last change: 21 Aug 2006 3
System Calls getrlimit(2)
When using the setrlimit() function, if the requested new
limit is RLIM_INFINITY, the new limit will be "no limit";
otherwise if the requested new limit is RLIM_SAVED_MAX, the
new limit will be the corresponding saved hard limit; other-
wise, if the requested new limit is RLIM_SAVED_CUR, the new
limit will be the corresponding saved soft limit; otherwise,
the new limit will be the requested value. In addition, if
the corresponding saved limit can be represented correctly
in an object of type rlim_t, then it will be overwritten
with the new limit.
The result of setting a limit to RLIM_SAVED_MAX or
RLIM_SAVED_CUR is unspecified unless a previous call to
getrlimit() returned that value as the soft or hard limit
for the corresponding resource limit.
A limit whose value is greater than RLIM_INFINITY is permit-
ted.
The exec family of functions also cause resource limits to
be saved. See exec(2).
RETURN VALUES
Upon successful completion, getrlimit() and setrlimit()
return 0. Otherwise, these functions return -1 and set errno
to indicate the error.
ERRORS
The getrlimit() and setrlimit() functions will fail if:
EFAULT The rlp argument points to an illegal
address.
EINVAL An invalid resource was specified; or in a
setrlimit() call, the new rlim_cur exceeds
the new rlim_max.
EPERM The limit specified to setrlimit() would
have raised the maximum limit value and
{PRIV_SYS_RESOURCE} is not asserted in the
effective set of the current process.
The setrlimit() function may fail if:
EINVAL The limit specified cannot be lowered
because current usage is already higher than
SunOS 5.10 Last change: 21 Aug 2006 4
System Calls getrlimit(2)
the limit.
USAGE
The getrlimit() and setrlimit() functions have transitional
interfaces for 64-bit file offsets. See lf64(5).
The rlimit functionality is now provided by the more general
resource control facility described on the setrctl(2) manual
page. The actions associated with the resource limits
described above are true at system boot, but an administra-
tor can modify the local configuration to modify signal
delivery or type. Application authors that utilize rlimits
for the purposes of resource awareness should investigate
the resource controls facility.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Interface Stability | Standard |
|_____________________________|_____________________________|
SEE ALSO
rctladm(1M), brk(2), exec(2), fork(2), open(2), setrctl(2),
sigaltstack(2), ulimit(2), getdtablesize(3C), malloc(3C),
signal(3C), signal.h(3HEAD), sysconf(3C), attributes(5),
lf64(5), privileges(5), resource_controls(5), standards(5)
SunOS 5.10 Last change: 21 Aug 2006 5
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This page was generated on Wed Sep 12 11:27:00 GMT 2007
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