path: root/usr/src/man/man2/getrlimit.2

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.TH GETRLIMIT 2 "Aug 21, 2006"
.SH NAME
getrlimit, setrlimit \- control maximum system resource consumption
.SH SYNOPSIS
.LP
.nf
#include <sys/resource.h>

\fBint\fR \fBgetrlimit\fR(\fBint\fR \fIresource\fR, \fBstruct rlimit *\fR\fIrlp\fR);
.fi

.LP
.nf
\fBint\fR \fBsetrlimit\fR(\fBint\fR \fIresource\fR, \fBconst struct rlimit *\fR\fIrlp\fR);
.fi

.SH DESCRIPTION
.sp
.LP
Limits on the consumption of a variety of system resources by a process and
each process it creates may be obtained with the \fBgetrlimit()\fR and set with
\fBsetrlimit()\fR functions.
.sp
.LP
Each call to either \fBgetrlimit()\fR or \fBsetrlimit()\fR 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 {\fBPRIV_SYS_RESOURCE\fR} asserted in the effective
set can raise a hard limit. Both hard and soft limits can be changed in a
single call to \fBsetrlimit()\fR subject to the constraints described above.
Limits may have an "infinite" value of \fBRLIM_INFINITY\fR. The \fIrlp\fR
argument is a pointer to \fBstruct\fR \fBrlimit\fR that includes the following
members:
.sp
.in +2
.nf
rlim_t    rlim_cur;     /* current (soft) limit */
rlim_t    rlim_max;     /* hard limit */
.fi
.in -2

.sp
.LP
The type \fBrlim_t\fR is an arithmetic data type to which objects of type
\fBint\fR, \fBsize_t\fR, and  \fBoff_t\fR can be cast without loss of
information.
.sp
.LP
The possible resources, their descriptions, and the actions taken when the
current limit is exceeded are summarized as follows:
.sp
.ne 2
.na
\fB\fBRLIMIT_CORE\fR\fR
.ad
.RS 17n
The maximum size of a core file in bytes that may be created by a process. A
limit of  \fB0\fR will prevent the creation of a core file. The writing of a
core file will terminate at this size.
.RE

.sp
.ne 2
.na
\fB\fBRLIMIT_CPU\fR\fR
.ad
.RS 17n
The maximum amount of CPU time in seconds used by a process. This is a soft
limit only.  The \fBSIGXCPU\fR signal is sent to the process. If the process is
holding or ignoring \fBSIGXCPU\fR, the behavior is scheduling class defined.
.RE

.sp
.ne 2
.na
\fB\fBRLIMIT_DATA\fR\fR
.ad
.RS 17n
The maximum size of a process's heap in bytes.  The \fBbrk\fR(2) function will
fail with  \fBerrno\fR set to  \fBENOMEM\fR.
.RE

.sp
.ne 2
.na
\fB\fBRLIMIT_FSIZE\fR\fR
.ad
.RS 17n
The maximum size of a file in bytes that may be created by a process. A limit
of  \fB0\fR will prevent the creation of a file.  The \fBSIGXFSZ\fR signal is
sent to the process. If the process is holding or ignoring  \fBSIGXFSZ\fR,
continued attempts to increase the size of a file beyond the limit will fail
with  \fBerrno\fR set to  \fBEFBIG\fR.
.RE

.sp
.ne 2
.na
\fB\fBRLIMIT_NOFILE\fR\fR
.ad
.RS 17n
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.
.RE

.sp
.ne 2
.na
\fB\fBRLIMIT_STACK\fR\fR
.ad
.RS 17n
The maximum size of a process's stack in bytes. The system will not
automatically grow the stack beyond this limit.
.sp
Within a process, \fBsetrlimit()\fR 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.
.sp
Within a multithreaded process, \fBsetrlimit()\fR has no impact on the stack
size limit for the calling thread if the calling thread is not the main thread.
A call to \fBsetrlimit()\fR for \fBRLIMIT_STACK\fR impacts only the main
thread's stack, and should be made only from the main thread, if at all.
.sp
The \fBSIGSEGV\fR signal is sent to the process. If the process is holding or
ignoring  \fBSIGSEGV\fR, or is catching  \fBSIGSEGV\fR and has not made
arrangements to use an alternate stack (see \fBsigaltstack\fR(2)), the
disposition of  \fBSIGSEGV\fR will be set to  \fBSIG_DFL\fR before it is sent.
.RE

.sp
.ne 2
.na
\fB\fBRLIMIT_VMEM\fR\fR
.ad
.RS 17n
The maximum size of a process's mapped address space in bytes.  If this limit
is exceeded, the \fBbrk\fR(2) and  \fBmmap\fR(2) functions will fail with
\fBerrno\fR set to  \fBENOMEM\fR. In addition, the automatic stack growth will
fail with the effects outlined above.
.RE

.sp
.ne 2
.na
\fB\fBRLIMIT_AS\fR\fR
.ad
.RS 17n
This is the maximum size of a process's total available memory, in bytes.  If
this limit is exceeded, the \fBbrk\fR(2), \fBmalloc\fR(3C), \fBmmap\fR(2) and
\fBsbrk\fR(2) functions will fail with \fBerrno\fR set to \fBENOMEM\fR. In
addition, the automatic stack growth will fail with the effects outlined above.
.RE

.sp
.LP
Because limit information is stored in the per-process information, the shell
builtin \fBulimit\fR command must directly execute this system call if it is to
affect all future processes created by the shell.
.sp
.LP
The value of the current limit of the following resources affect these
implementation defined parameters:
.sp

.sp
.TS
c c
l l .
Limit	Implementation Defined Constant
\fBRLIMIT_FSIZE\fR	\fBFCHR_MAX\fR
\fBRLIMIT_NOFILE\fR	\fBOPEN_MAX\fR
.TE

.sp
.LP
When using the \fBgetrlimit()\fR function, if a resource limit can be
represented correctly in an object of type  \fBrlim_t\fR, 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
\fBRLIM_SAVED_MAX\fR; otherwise the value returned is \fBRLIM_SAVED_CUR\fR.
.sp
.LP
When using the \fBsetrlimit()\fR function, if the requested new limit is
\fBRLIM_INFINITY\fR, the new limit will be "no limit"; otherwise if the
requested new limit is \fBRLIM_SAVED_MAX\fR, the new limit will be the
corresponding saved hard limit; otherwise, if the requested new limit is
\fBRLIM_SAVED_CUR\fR, 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
\fBrlim_t\fR, then it will be overwritten with the new limit.
.sp
.LP
The result of setting a limit to \fBRLIM_SAVED_MAX\fR or \fBRLIM_SAVED_CUR\fR
is unspecified unless a previous call to  \fBgetrlimit()\fR returned that value
as the soft or hard limit for the corresponding resource limit.
.sp
.LP
A limit whose value is greater than \fBRLIM_INFINITY\fR is permitted.
.sp
.LP
The \fBexec\fR family of functions also cause resource limits to be saved.  See
\fBexec\fR(2).
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBgetrlimit()\fR and \fBsetrlimit()\fR return
\fB0\fR. Otherwise, these functions return \fB\(mi1\fR and set \fBerrno\fR to
indicate the error.
.SH ERRORS
.sp
.LP
The \fBgetrlimit()\fR and \fBsetrlimit()\fR functions will fail if:
.sp
.ne 2
.na
\fB\fBEFAULT\fR\fR
.ad
.RS 10n
The \fIrlp\fR argument points to an illegal address.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
An invalid \fIresource\fR was specified; or in a \fBsetrlimit()\fR call, the
new \fBrlim_cur\fR exceeds the new \fBrlim_max\fR.
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 10n
The limit specified to \fBsetrlimit()\fR would have raised the maximum limit
value and {\fBPRIV_SYS_RESOURCE\fR} is not asserted in the effective set of the
current process.
.RE

.sp
.LP
The \fBsetrlimit()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The limit specified cannot be lowered because current usage is already higher
than the limit.
.RE

.SH USAGE
.sp
.LP
The \fBgetrlimit()\fR and \fBsetrlimit()\fR functions have transitional
interfaces for 64-bit file offsets.  See \fBlf64\fR(7).
.sp
.LP
The rlimit functionality is now provided by the more general resource control
facility described on the \fBsetrctl\fR(2) manual page. The actions associated
with the resource limits described above are true at system boot, but an
administrator 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.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR brk (2),
.BR exec (2),
.BR fork (2),
.BR open (2),
.BR setrctl (2),
.BR sigaltstack (2),
.BR ulimit (2),
.BR getdtablesize (3C),
.BR malloc (3C),
.BR signal (3C),
.BR sysconf (3C),
.BR signal.h (3HEAD),
.BR attributes (7),
.BR lf64 (7),
.BR privileges (7),
.BR resource_controls (7),
.BR standards (7),
.BR rctladm (8)