getrlimit(2) UNIX System V 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);
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 an effective user ID or
superuser 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 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
_______________________________________________
RLIMIT_CORE The maximum The writing of
size of a core a core file
file in bytes will terminate
that may be at this size.
created by a
process. A
limit of 0 will
prevent the
creation of a
core file.
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getrlimit(2) UNIX System V getrlimit(2)
RLIMIT_CPU The maximum SIGXCPU is sent
amount of CPU to the process.
time in seconds If the process
used by a is holding or
process. ignoring
SIGXCPU, the
behavior is
scheduling
class defined.
RLIMIT_DATA The maximum brk(2) will
size of a fail with errno
process's heap set to ENOMEM.
in bytes.
Resources Description Action
__________________________________________________
RLIMIT_FSIZE The maximum SIGXFSZ is sent
size of a file to the process.
in bytes that If the process
may be created is holding or
by a process. ignoring
A limit of 0 SIGXFSZ,
will prevent continued
the creation of attempts to
a file. increase the
size of a file
beyond the
limit will fail
with errno set
to EFBIG.
RLIMIT_NOFILE The maximum Functions that
number of open create new file
file descriptors
descriptors will fail with
that the errno set to
process can EMFILE.
have.
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getrlimit(2) UNIX System V getrlimit(2)
RLIMIT_STACK The maximum SIGSEGV is sent
size of a to the process.
process's stack If the process
in bytes. The is holding or
system will not ignoring
automatically SIGSEGV, or is
grow the stack catching
beyond this SIGSEGV and has
limit. not made
arrangements to
use an
alternate stack
[see
sigaltstack(2)],
the disposition
of SIGSEGV will
be set to
SIGDFL before
it is sent.
RLIMIT_VMEM The maximum brk(2) and
size of a mmap(2)
process's functions will
mapped address fail with errno
space in bytes. 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 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
_______________________________________________
RLIMIT_FSIZE FCHR_MAX
RLIMIT_NOFILE OPEN_MAX
RETURN VALUE
Upon successful completion, the functions getrlimit and setrlimit return
a value of 0; otherwise, they return a value of -1 and set errno to
indicate an error.
ERRORS
Under the following conditions, the functions getrlimit and setrlimit
fail and set errno to:
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getrlimit(2) UNIX System V getrlimit(2)
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 caller is the superuser
SEE ALSO
malloc(3C), open(2), sigaltstack(2), signal(5).
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