GETRLIMIT(2) | System Calls Manual | GETRLIMIT(2) |
getrlimit
, setrlimit
—
#include <sys/resource.h>
int
getrlimit
(int
resource, struct rlimit
*rlp);
int
setrlimit
(int
resource, const struct
rlimit *rlp);
getrlimit
() call, and set with the
setrlimit
() call. Resources of an arbitrary process
can be obtained/changed using
sysctl(3).
The resource parameter is one of the following:
RLIMIT_AS
RLIMIT_CORE
RLIMIT_CPU
RLIMIT_DATA
RLIMIT_FSIZE
RLIMIT_MEMLOCK
RLIMIT_NOFILE
RLIMIT_NPROC
RLIMIT_NTHR
RLIMIT_RSS
RLIMIT_SBSIZE
SO_RCVBUF
and SO_SNDBUF
options.RLIMIT_STACK
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 or file size is exceeded), but it will be allowed to continue execution until it reaches the hard limit (or modifies its resource limit). The rlimit structure is used to specify the hard and soft limits on a resource,
struct rlimit { rlim_t rlim_cur; /* current (soft) limit */ rlim_t rlim_max; /* hard limit */ };
Only the super-user may raise the maximum limits. Other users may only 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
.
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. Thus, shells provide built-in
commands to change the limits (limit
for
csh(1), or
ulimit
for
sh(1)).
The system refuses to extend the data or stack space when the
limits would be exceeded in the normal way: a
brk(2) call fails if the data
space limit is reached. When the stack limit is reached, the process
receives a segmentation fault (SIGSEGV
); if this
signal is not caught by a handler using the signal stack, this signal will
kill the process.
A file I/O operation that would create a file larger that the
process' soft limit will cause the write to fail and a signal
SIGXFSZ
to be generated; this normally terminates
the process, but may be caught. When the soft CPU time limit is exceeded, a
signal SIGXCPU
is sent to the offending process.
getrlimit
() and setrlimit
()
will fail if:
EFAULT
]EINVAL
]setrlimit
() call, the specified
rlim_cur exceeds the specified
rlim_max.EPERM
]setrlimit
() would have
raised the maximum limit value, and the caller is not the super-user.The setrlimit
() function may fail if:
EINVAL
]setrlimit
() cannot be
lowered, because current usage is already higher than the limit.getrlimit
() function call appeared in
4.2BSD.
RLIMIT_RSS
is not implemented in
uvm(9) which means that process
memory size limits are not enforced.
June 8, 2012 | NetBSD 9.0 |