getrlimit(2) SYSTEM CALLS getrlimit(2)
NAME
getrlimit, setrlimit - control maximum system resource con-
sumption
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 informa-
tion. 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) SYSTEM CALLS getrlimit(2)
RLIMIT_CPU The maximum SIGXCPU is sent
amount of CPU to the process.
time in seconds If the process
used by a pro- is holding or
cess. 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, con-
will prevent tinued attempts
the creation of to increase the
a file. 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 descrip- descriptors
tors that the will fail with
process can errno set to
have. EMFILE.
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getrlimit(2) SYSTEM CALLS 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 SIG-
automatically SEGV, or is
grow the stack catching SIG-
beyond this SEGV and has
limit. not made
arrangements to
use an alter-
nate 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) func-
process's tions will fail
mapped address with errno set
space in bytes. to ENOMEM. In
addition, the
automatic stack
growth will
fail with the
effects out-
lined 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 con-
stants:
Limit Implementation Defined Constant
_______________________________________________
RLIMIT_FSIZE FCHR_MAX
RLIMIT_NOFILE OPEN_MAX
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.
ERRORS
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.
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getrlimit(2) SYSTEM CALLS getrlimit(2)
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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