getrlimit.2

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 2 代码 · 共 147 行

.\" SCCSID: @(#)getrlimit.2	2.5	8/10/87
.TH getrlimit 2
.SH Name
getrlimit, setrlimit \- control maximum system resource consumption
.SH Syntax
.ft B
.nf
#include <sys/time.h>
#include <sys/resource.h>
.PP
.ft B
getrlimit(resource, rlp)
int resource;
struct rlimit *rlp;
.PP
.ft B
setrlimit(resource, rlp)
int resource;
struct rlimit *rlp;
.fi
.ft R
.SH Description
.NXR "getrlimit system call"
.NXR "setrlimit system call"
.NXR "process" "controlling resource consumption"
Limits on the consumption of system resources by the current process
and each process it creates can be obtained with the
.PN getrlimit
call and set with the
.PN setrlimit
call.  
.PP
The
.I resource
parameter is one of the following:
.NXR "getrlimit system call" "parameter list"
.TP 17
RLIMIT_CPU
the maximum amount of cpu time (in milliseconds) to be used by
each process.
.TP 17
RLIMIT_FSIZE
the largest size, in bytes, of any single file that may be created.
.TP 17
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
.PN sbrk 
system call.
.TP 17
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 
.PN sbrk 
system call.
.TP 17
RLIMIT_CORE
the largest size, in bytes, of a 
.I core
file that may be created.
.TP 17
RLIMIT_RSS
the maximum size, in bytes, to which a process's resident 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 unfavorable
scheduling priority being assigned to the process.
.PP
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 
.I rlimit
structure is used to specify the hard and soft limits on a resource, as
shown:
.NXR "soft limit" "specifying"
.NXR "hard limit" "specifying"
.EX
struct rlimit {
	int	rlim_cur;	/* current (soft) limit */
	int	rlim_max;	/* hard limit */
};
.EE
.PP
Only the superuser may raise the maximum limits.  Other users
may alter 
.I rlim_cur
within the range from 0 to 
.I rlim_max
or (irreversibly) lower
.IR rlim_max .
.PP
An \*(lqinfinite\*(rq value for a limit is defined as RLIM_INFINITY
(0x7\&f\&f\&f\&f\&f\&f\&f).
.PP
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;
.I limit
is thus a built-in command to 
.PN csh .
.PP
The system refuses to extend the data or stack space when the limits
would be exceeded in the normal way: a
.I 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.
.PP
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.
.SH Return Values
A 0 return value indicates that the call succeeded, changing
or returning the resource limit.   A return value of \-1 indicates
that an error occurred, and an error code is stored in the global
location \fIerrno\fP.
.SH Environment
.SS System Five
When your program is compiled in the System V environment, the SIGXFSZ signal is not
generated.
.SH Diagnostics
The 
.PN getrlimit
call fails under the following conditions:
.TP 15
[EFAULT]
The address specified for \fIrlp\fP is invalid.
.TP 15
[EPERM]
The limit specified to 
.PN setrlimit
would have raised the maximum limit value,
and the caller is not the superuser.
.TP 15
[EINVAL]
Resource is greater than or equal to RLIM_NLIMITS.
.SH See Also
csh(1), quota(2)