Originální popis anglicky:
getrlimit, setrlimit - control maximum resource consumption
Návod, kniha: POSIX Programmer's Manual
#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 process' data segment, 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 a process' 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 a process' total available
memory, 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.
None.
None.
exec() ,
fork() ,
malloc() ,
open() ,
sigaltstack() ,
sysconf() ,
ulimit() , the Base
Definitions volume of IEEE Std 1003.1-2001,
<stropts.h>,
<sys/resource.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html
.
