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GETRLIMIT(3P) POSIX Programmer's Manual GETRLIMIT(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
getrlimit, setrlimit — control maximum resource consumption
#include <sys/resource.h>
int getrlimit(int resource, struct rlimit *rlp);
int setrlimit(int resource, const struct rlimit *rlp);
The getrlimit() function shall get, and the setrlimit() function
shall set, limits on the consumption of a variety of resources.
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 represented by an rlimit structure. The rlim_cur member
specifies the current or soft limit and the rlim_max member specifies
the maximum or 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 appropriate
privileges 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.
The value RLIM_INFINITY, defined in <sys/resource.h>, shall be
considered to be larger than any other limit value. If a call to
getrlimit() returns RLIM_INFINITY for a resource, it means the
implementation shall not enforce limits on that resource. Specifying
RLIM_INFINITY as any resource limit value on a successful call to
setrlimit() shall inhibit enforcement of that resource limit.
The following resources are defined:
RLIMIT_CORE This is the maximum size of a core file, in bytes, that
may be created by a process. A limit of 0 shall prevent
the creation of a core file. If this limit is exceeded,
the writing of a core file shall terminate at this
size.
RLIMIT_CPU This is the maximum amount of CPU time, in seconds,
used by a process. If this limit is exceeded, SIGXCPU
shall be generated for the process. If the process is
catching or ignoring SIGXCPU, or all threads belonging
to that process are blocking SIGXCPU, the behavior is
unspecified.
RLIMIT_DATA This is the maximum size of a data segment of the
process, in bytes. If this limit is exceeded, the
malloc() function shall fail with errno set to
[ENOMEM].
RLIMIT_FSIZE This is the maximum size of a file, in bytes, that may
be created by a process. If a write or truncate
operation would cause this limit to be exceeded,
SIGXFSZ shall be generated for the thread. If the
thread is blocking, or the process is catching or
ignoring SIGXFSZ, continued attempts to increase the
size of a file from end-of-file to beyond the limit
shall fail with errno set to [EFBIG].
RLIMIT_NOFILE This is a number one greater than the maximum value
that the system may assign to a newly-created
descriptor. If this limit is exceeded, functions that
allocate a file descriptor shall fail with errno set to
[EMFILE]. This limit constrains the number of file
descriptors that a process may allocate.
RLIMIT_STACK This is the maximum size of the initial thread's stack,
in bytes. The implementation does not automatically
grow the stack beyond this limit. If this limit is
exceeded, SIGSEGV shall be generated for the thread. If
the thread is blocking SIGSEGV, or the process is
ignoring or catching SIGSEGV and has not made
arrangements to use an alternate stack, the disposition
of SIGSEGV shall be set to SIG_DFL before it is
generated.
RLIMIT_AS This is the maximum size of total available memory of
the process, in bytes. If this limit is exceeded, the
malloc() and mmap() functions shall fail with errno set
to [ENOMEM]. In addition, the automatic stack growth
fails with the effects outlined above.
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 shall be RLIM_SAVED_MAX; otherwise, the value returned
shall be RLIM_SAVED_CUR.
When using the setrlimit() function, if the requested new limit is
RLIM_INFINITY, the new limit shall be ``no limit''; otherwise, if the
requested new limit is RLIM_SAVED_MAX, the new limit shall be the
corresponding saved hard limit; otherwise, if the requested new limit
is RLIM_SAVED_CUR, the new limit shall be the corresponding saved
soft limit; otherwise, the new limit shall be the requested value. In
addition, if the corresponding saved limit can be represented
correctly in an object of type rlim_t then it shall 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.
The determination of whether a limit can be correctly represented in
an object of type rlim_t is implementation-defined. For example, some
implementations permit a limit whose value is greater than
RLIM_INFINITY and others do not.
The exec family of functions shall cause resource limits to be saved.
Upon successful completion, getrlimit() and setrlimit() shall return
0. Otherwise, these functions shall return −1 and set errno to
indicate the error.
The getrlimit() and setrlimit() functions shall fail if:
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 the calling process does not have
appropriate privileges.
The setrlimit() function may fail if:
EINVAL The limit specified cannot be lowered because current usage is
already higher than the limit.
The following sections are informative.
None.
If a process attempts to set the hard limit or soft limit for
RLIMIT_NOFILE to less than the value of {_POSIX_OPEN_MAX} from
<limits.h>, unexpected behavior may occur.
If a process attempts to set the hard limit or soft limit for
RLIMIT_NOFILE to less than the highest currently open file descriptor
+1, unexpected behavior may occur.
It should be noted that RLIMIT_STACK applies ``at least'' to the
stack of the initial thread in the process, and not to the sum of all
the stacks in the process, as that would be very limiting unless the
value is so big as to provide no value at all with a single thread.
None.
exec(1p), fork(3p), malloc(3p), open(3p), sigaltstack(3p),
sysconf(3p), ulimit(3p)
The Base Definitions volume of POSIX.1‐2008, stropts.h(0p),
sys_resource.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 GETRLIMIT(3P)
Pages that refer to this page: sys_resource.h(0p), exec(3p), fclose(3p), fflush(3p), fputc(3p), fseek(3p), malloc(3p), setrlimit(3p), ulimit(3p), write(3p), limits.conf(5)
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