getrlimit(2) System Calls Manual 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);
[Tru64 UNIX] The following declaration of the setrlimit() function does not conform to current standards and is supported only for back-
ward compatibility:
int setrlimit(
int resource1,
struct rlimit *rlp);
[Tru64 UNIX] Application developers may want to specify an #include statement for <sys/time.h> before the one for <sys/resource.h> if pro-
grams are being developed for multiple platforms. The additional #include statement is not required on Tru64 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(): XSH4.2
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
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 maxi-
mum 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 sup-
port for more than 4096 open file descriptors. See the discussion of the open_max_hard and open_max_soft 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 getr-
limit() 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.
[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.
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: [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.
RELATED INFORMATION
Functions: quotactl(2), setsysinfo(2), sigaction(2), sigstack(2), sigvec(2), ulimit(3)
Standards: standards(5) delim off
getrlimit(2)