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getrlimit(2)
NAME
getrlimit, setrlimit - Controls maximum system resource consumption
SYNOPSIS
#include <sys/resource.h>
int getrlimit(
int resource1,
struct rlimit *rlp);
int setrlimit(
int resource1,
const struct rlimit *rlp);
[Digital] The following declaration of the setrlimit() function does not
conform to current standards and is supported only for backward
compatibility:
int setrlimit(
int resource1,
struct rlimit *rlp);
[Digital] Application developers may want to specify an #include statement
for <sys/time.h> before the one for <sys/resource.h> if programs are being
developed for multiple platforms. The additional #include statement is not
required on DIGITAL UNIX systems or by ISO or X/Open standards, but may be
required on other vendors' systems that conform to these standards.
STANDARDS
Interfaces documented on this reference page conform to industry standards
as follows:
getrlimit(), setrlimit(): XPG4-UNIX
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
resource1
Specifies one of the following values:
RLIMIT_AS
The maximum size, in bytes, of the total memory available to a
process. Exceeding this limit causes the brk(), malloc(), mmap(),
and sbrk() functions to fail with errno set to [ENOMEM]. Also, the
automatic stack growth will fail with the effects described under
RLIMIT_STACK.
RLIMIT_CORE
The largest size, in bytes, of a core file that can be created. A
limit of 0 (zero) prevents the process from creating a core file.
If a process exceeds this limit, any remaining data to be written
to the core file is lost.
RLIMIT_CPU
The maximum amount of CPU time (in seconds) to be used by a
process. If the process exceeds this limit, the system sends the
SIGXCPU signal to the process.
RLIMIT_DATA
The maximum size, in bytes, of a process's data segment. Exceeding
this limit causes the brk(), malloc(), mmap(), and sbrk() functions
to fail with errno set to [ENOMEM].
RLIMIT_FSIZE
The maximum size, in bytes, of any single file that can be created.
A limit of 0 (zero) prevents the process from creating a file. If
a write or truncate operation would cause this limit to be
exceeded, the system generates the SIGXFSZ signal. If the process
is blocking, catching, or ignoring SIGXFSZ, continued attempts to
increase the size of a file from end-of-file to beyond the limit
will fail with errno set to [EFBIG].
RLIMIT_NOFILE
The maximum number of open file descriptors that the process can
have. Any functions that attempt to create new file descriptors
when the maximum hard limit has been reached will fail with errno
set to [EMFILE].
[Digital] The default maximum is 4096 file descriptors. The
maximum can be 64K file descriptors when a process has enabled
support for greater than 4096 open file descriptors.
RLIMIT_RSS
[Digital] The maximum size, in bytes, to which a process's
resident set size can grow. This value imposes a limit on the
amount of physical memory to be given to a process. If memory is
in short supply, the system prefers to take memory from processes
that are exceeding their declared resident set size.
RLIMIT_STACK
The maximum size, in bytes, of a process's stack. The system will
not automatically grow the stack beyond this limit. If this limit
is exceeded, SIGSEGV is generated for the process. If the process
is blocking or ignoring SIGSEGV, or is catching SIGSEGV and has not
made arrangements to use an alternate stack, the disposition of
SIGSEGV is set to SIG_DFL before it is generated.
rlp Points to the rlimit structure, which contains the current soft and
hard limits. For the getrlimit() function, the requested limits are
returned in this structure; for the setrlimit() function, the desired
new limits are specified here.
DESCRIPTION
The getrlimit() function obtains the limits on the consumption of system
resources by the current process and each process it creates. You use the
setrlimit() function to set these resources.
Each resource limit is specified as either a soft limit or a hard limit.
When a soft limit is exceeded (for example, if the CPU time is exceeded), a
process can receive a signal until it reaches the hard limit or until it
modifies its resource limit. The rlimit structure is used to specify the
hard and soft limits on a resource, as defined in the sys/resource.h header
file.
The calling process must have superuser privilege in order to raise the
maximum limits. An unprivileged process can alter the rlim_cur field of
the rlimit structure within the range from 0 (zero) to rlim_max or can
(irreversibly) lower rlim_max.
An infinite value for a limit is defined as RLIM_INFINITY.
Because this information is stored in the per-process information, and
inherited by fork(), the setrlimit() function should be executed directly
by the shell in order to affect all future processes created by the shell.
Thus, limit is a built-in command to the shells.
NOTES
The ulimit() function is implemented in terms of setrlimit(). Therefore,
the two interfaces should not be used in the same program. The result of
doing so is undefined.
[Digital] When compiled in the X/Open UNIX environment, calls to the
setrlimit() function are internally renamed by prepending _E to the
function name. When you are debugging a module that includes the
setrlimit() function and for which _XOPEN_SOURCE_EXTENDED has been defined,
use _Esetrlimit to refer to the setrlimit() call. See standards(5) for
further information.
RETURN VALUES
Upon successful completion, these functions return a value of 0 (zero).
Otherwise, the functions return a value of -1 and set errno to indicate the
error.
ERRORS
If the getrlimit() or setrlimit() function fails, errno might be set to one
of the following values:
[EFAULT]
[Digital] The address specified for the rlp parameter is invalid.
[EINVAL]
An invalid resource was specified, or the new rlim_cur specified in a
setrlimit() call exceeds the new rlim_max specified in that same call.
[EPERM]
The limit specified to the setrlimit() function would have raised the
maximum limit value, and the calling process does not have appropriate
privilege.
RELATED INFORMATION
Functions: quotactl(2), setsysinfo(2), sigaction(2), sigstack(2), sigvec(2)
Routines: ulimit(3)
Standards: standards(5)