getrlimit(2)getrlimit(2)Name
getrlimit, setrlimit - control maximum system resource consumption
Syntax
#include <sys/time.h>
#include <sys/resource.h>
getrlimit(resource, rlp)
int resource;
struct rlimit *rlp;
setrlimit(resource, rlp)
int resource;
struct rlimit *rlp;
Description
Limits on the consumption of system resources by the current process
and each process it creates can be obtained with the call and set with
the call.
The resource parameter is one of the following:
RLIMIT_CPU the maximum amount of cpu time (in milliseconds) to be
used by each process.
RLIMIT_FSIZE the largest size, in bytes, of any single file that
may be created.
RLIMIT_DATA the maximum size, in bytes, of the data segment for a
process. This limit defines how far a program can
extend its break with the system call.
RLIMIT_STACK the maximum size, in bytes, of the stack segment for a
process. This limit defines how far a program's stack
segment can be extended, either automatically by the
system or explicitly by a user, with the system call.
RLIMIT_CORE the largest size, in bytes, of a core file that may be
created.
RLIMIT_RSS the maximum size, in bytes, to which a process's resi‐
dent set size may grow when there is a shortage of
free physical memory. Exceeding this limit when free
physical memory is in short supply results in an unfa‐
vorable scheduling priority being assigned to the
process.
A resource limit is specified as a soft limit and a hard limit. When a
soft limit is exceeded, a process may receive a signal (for example, if
the cpu time is exceeded), but it will be allowed to continue execution
until it reaches the hard limit (or modifies its resource limit). The
system uses just the soft limit field of the resources RLIMIT_CORE and
RLIMIT_RSS. The rlimit structure is used to specify the hard and soft
limits on a resource, as shown:
struct rlimit {
int rlim_cur; /* current (soft) limit */
int rlim_max; /* hard limit */
};
Only the superuser may raise the maximum limits. Other users may alter
rlim_cur within the range from 0 to rlim_max or (irreversibly) lower
rlim_max.
An “infinite” value for a limit is defined as RLIM_INFINITY
(0x7fffffff).
Because this information is stored in the per-process information, this
system call must be executed directly by the shell if it is to affect
all future processes created by the shell; limit is thus a built-in
command to
The system refuses to extend the data or stack space when the limits
would be exceeded in the normal way: a break call fails if the data
space limit is reached, or the process is killed when the stack limit
is reached. Because the stack cannot be extended, there is no way to
send a signal.
A file I/O operation that creates too large a file causes the SIGXFSZ
signal to be generated. This condition normally terminates the process,
but may be caught. When the soft cpu time limit is exceeded, a signal
SIGXCPU is sent to the process.
Return Values
A 0 return value indicates that the call succeeded, changing or return‐
ing the resource limit. A return value of -1 indicates that an error
occurred, and an error code is stored in the global location errno.
Environment
System Five
When your program is compiled in the System V environment, the SIGXFSZ
signal is not generated.
Diagnostics
The call fails under the following conditions:
[EFAULT] The address specified for rlp is invalid.
[EPERM] The limit specified to would have raised the maximum
limit value, and the caller is not the superuser.
[EINVAL] Resource is greater than or equal to RLIM_NLIMITS.
See Alsocsh(1), quota(2)getrlimit(2)