getrlimit(2) SDK R4.11 getrlimit(2)
NAME
getrlimit, setrlimit - control maximum system resource consumption
SYNOPSIS
#include <sys/time.h>
#include <sys/resource.h>
int getrlimit(int resource, struct rlimit *rlp);
int setrlimit(int resource, const struct rlimit *rlp);
where:
resource The resource for which the limits are to be returned or
set.
rlp A pointer to a structure into which the limit values are to
be placed or read from
DESCRIPTION
Limits on the consumption of a variety of system resources by a
process and each process it creates may be obtained with getrlimit
and set with setrlimit.
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
appropriate privilege can raise a hard limit. For systems supporting
the DG/UX Capability Option, appropriate privilege is defined as
having one or more specific capabilities enabled in the effective
capability set of the calling process. See capdefaults(5) for the
default capability for this system call.
On systems without the DG/UX Capability Option, appropriate privilege
means that the process has an effective UID of root. See the
appropriateprivilege(5) man page for more information.
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 RLIMINFINITY. rlp is a pointer to
struct rlimit that includes the following members:
rlimt rlimcur; /* current (soft) limit */
rlimt rlimmax; /* hard limit */
rlimt is an arithmetic data type to which objects of type int,
sizet, and offt can be cast without loss of information.
The possible resources, their descriptions, and the actions taken
when current limit is exceeded, are summarized in the table below:
Resources Description Action
---------------------------------------------------------------
RLIMITCORE The maximum size of The writing of a core
a core file in bytes file will terminate at
that may be created this size.
by a process. A
limit of 0 will
prevent the creation
of a core file.
RLIMITCPU The maximum amount SIGXCPU is sent to the
of CPU time in process. If the process
seconds used by a is holding or ignoring
process. SIGXCPU, the behavior is
scheduling class defined.
RLIMITDATA The maximum size of brk(2) will fail with
a process's heap in errno set to ENOMEM.
bytes.
Resources Description Action
---------------------------------------------------------------
RLIMITFSIZE The maximum size of SIGXFSZ is sent to the
a file in bytes that process. If the process
may be created by a is holding or ignoring
process. A limit of SIGXFSZ, continued
0 will prevent the attempts to increase the
creation of a file. size of a file beyond the
limit will fail with
errno set to EFBIG.
RLIMITNOFILE The maximum number Functions that create new
of open file file descriptors will
descriptors that the fail with errno set to
process can have. EMFILE. Or, when
attempting an fcntl()
"FDUPFD", return EINVAL.
RLIMITSTACK The maximum size of SIGSEGV is sent to the
a process's stack in process. If the process
bytes. The system is holding or ignoring
will not SIGSEGV, or is catching
automatically grow SIGSEGV and has not made
the stack beyond arrangements to use an
this limit. alternate stack [see
sigaltstack(2)], the
disposition of SIGSEGV
will be set to SIGDFL
before it is sent.
RLIMITAS The maximum size of brk(2) and mmap(2)
a process's mapped functions will fail with
address space in errno set to ENOMEM.
bytes. This same Also, attempting an
resource may be exec(2) on an image
accessed by setting greater than this limit
resource to will fail, setting errno
RLIMITVMEM. to ENOMEM.
RLIMITRSS The maximum size in The kernel limits a
bytes to which a process' resident set
process' resident size to RLIMITRSS bytes.
set size can grow.
Because limit information is stored in the per-process information,
the shell builtin ulimit 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 constants:
Limit Implementation Defined Constant
------------------------------------------------
RLIMITFSIZE FCHRMAX
RLIMITNOFILE OPENMAX
RETURN VALUE
Upon successful completion, the function getrlimit returns a value of
0; otherwise, it returns a value of -1 and sets errno to indicate an
error.
DIAGNOSTICS
Under the following conditions, the functions getrlimit and setrlimit
fail and set errno to:
EINVAL if an invalid resource was specified; or in a setrlimit call,
the new rlimcur exceeds the new rlimmax.
EPERM if the limit specified to setrlimit would have raised the
maximum limit value, and the calling process does not have
appropriate privilege
SEE ALSO
open(2), sbrk(2), sigaltstack(2), ulimit(2), malloc(3C),
appropriateprivilege(5), signal(5).
capdefaults(5).
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