getrlimit, setrlimit - Control maximum system resource
struct rlimit *rlp ); int setrlimit(
const struct rlimit *rlp );
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 Tru64 UNIX systems or by ISO or XSH standards,
but may be required on other vendors' systems that conform
to these standards.
[Tru64 UNIX] The following declaration of the setrlimit()
function does not conform to current standards and is supported
only for backward compatibility: int setrlimit
struct rlimit *rlp );
Interfaces documented on this reference page conform to
industry standards as follows:
getrlimit(), setrlimit(): XSH4.2, XSH5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Specifies one of the following values: 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. 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. 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. 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]. 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 write attempts
to extend a file already at its limit or a 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]. 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].
[Tru64 UNIX] The default maximum is 4096 file
descriptors. The maximum can be 64K file descriptors
when a process has enabled support for more
than 4096 open file descriptors. See the discussion
of the open_max_hard and open_max_soft system
attributes in sys_attrs_proc(5) for information
about increasing the soft and hard limits for open
file descriptors. [Tru64 UNIX] 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 that can 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. 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. 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
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)
An infinite value for a limit is defined as RLIM_INFINITY,
which means that no limit is enforced for the specified
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,
rlimit is a built-in command to the shells.
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.
[Tru64 UNIX] 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 additional information.
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.
If the getrlimit() or setrlimit() function fails, errno is
set to one of the following values for the specified conditions:
[Tru64 UNIX] The address specified for the rlp
parameter is invalid. 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. The
limit specified to the setrlimit() function would have
raised the maximum limit value, and the calling process
does not have appropriate privilege.
Functions: quotactl(2), setsysinfo(2), sigaction(2),
sigstack(2), sigvec(2), ulimit(3)
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