System Calls getrlimit(2)
NAME
getrlimit, setrlimit - control maximum system resource con-
sumptionSYNOPSIS
#include
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 obtainedwith 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 ofRLIM_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 willSunOS 5.11 Last change: 21 Aug 2006 1
System Calls getrlimit(2)
terminate at this size.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 orignoring SIGXCPU, the behavior is schedul-
ing 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 process is holding or ignoring SIGXFSZ, continued 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 exe-
cution 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
thread's stack, and should be made onlySunOS 5.11 Last change: 21 Aug 2006 2
System Calls getrlimit(2)
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 ofSIGSEGV 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 ConstantRLIMIT_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 correspondingsaved hard limit, the value returned is RLIM_SAVED_MAX; oth-
erwise the value returned is RLIM_SAVED_CUR.
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System Calls getrlimit(2)
When using the setrlimit() function, if the requested newlimit 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 correctlyin 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 asetrlimit() 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 effec-
tive 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 the limit.SunOS 5.11 Last change: 21 Aug 2006 4
System Calls getrlimit(2)
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 limitsdescribed 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 5.11 Last change: 21 Aug 2006 5