GETRLIMIT(2) | System Calls Manual | GETRLIMIT(2) |
getrlimit
,
setrlimit
— control maximum
system resource consumption
#include
<sys/resource.h>
int
getrlimit
(int
resource, struct rlimit
*rlp);
int
setrlimit
(int
resource, const struct
rlimit *rlp);
Limits on the consumption of system resources by the current
process and each process it creates may be obtained with the
getrlimit
()
call, and set with the
setrlimit
()
call.
The resource parameter is one of the following:
RLIMIT_CORE
RLIMIT_CPU
RLIMIT_DATA
RLIMIT_FSIZE
RLIMIT_MEMLOCK
RLIMIT_NOFILE
RLIMIT_NPROC
RLIMIT_RSS
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 superuser 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
.
A value of RLIM_SAVED_CUR
or RLIM_SAVED_MAX
will be stored in
rlim_cur or rlim_max
respectively by
getrlimit
()
if the value for the current or maximum resource limit cannot be stored in
an rlim_t
. The values
RLIM_SAVED_CUR
and
RLIM_SAVED_MAX
should not be used in a call to
setrlimit
()
unless they were returned by a previous call to
getrlimit
().
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
csh(1) and
ulimit
is the
sh(1) equivalent.
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 than 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.
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
getrlimit
() and
setrlimit
() will fail if:
EFAULT
]EINVAL
]In addition, setrlimit
() may return the
following errors:
csh(1), sh(1), quotactl(2), sigaction(2), sigaltstack(2), sysctl(2)
The getrlimit
() and
setrlimit
() functions conform to
IEEE Std 1003.1-2008 (“POSIX.1”).
The RLIMIT_MEMLOCK
,
RLIMIT_NPROC
, and RLIMIT_RSS
resources are non-standard extensions.
The getrlimit
() and
setrlimit
() system calls first appeared in
4.1cBSD.
The RLIMIT_AS
resource is missing.
January 12, 2018 | OpenBSD-7.0 |