[apple/xnu.git] / bsd / man / man2 / getrlimit.2

.\"	$NetBSD: getrlimit.2,v 1.8 1995/10/12 15:40:58 jtc Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)getrlimit.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt GETRLIMIT 2
.Os BSD 4
.Sh NAME
.Nm getrlimit ,
.Nm setrlimit
.Nd control maximum system resource consumption
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/time.h>
.Fd #include <sys/resource.h>
.Ft int
.Fn getrlimit "int resource" "struct rlimit *rlp"
.Ft int
.Fn setrlimit "int resource" "const struct rlimit *rlp"
.Sh DESCRIPTION
Limits on the consumption of system resources by the current process
and each process it creates may be obtained with the
.Fn getrlimit
call, and set with the
.Fn setrlimit
call.  
.Pp
The
.Fa resource
parameter is one of the following:
.Bl -tag -width RLIMIT_FSIZEAA
.It Li RLIMIT_CORE
The largest size (in bytes)
.Xr core
file that may be created.
.It Li RLIMIT_CPU
The maximum amount of cpu time (in seconds) to be used by
each process.
.It Li RLIMIT_DATA
The maximum size (in bytes) of the data segment for a process;
this defines how far a program may extend its break with the
.Xr sbrk 2
system call.
.It Li RLIMIT_FSIZE
The largest size (in bytes) file that may be created.
.It Li RLIMIT_MEMLOCK
The maximum size (in bytes) which a process may lock into memory
using the
.Xr mlock 2
function.
.It Li RLIMIT_NOFILE
The maximum number of open files for this process.
.It Li RLIMIT_NPROC
The maximum number of simultaneous processes for this user id.
.It Li RLIMIT_RSS
The maximum size (in bytes) to which a process's resident set size may
grow.
This imposes a limit on the amount of physical memory to be given to
a process; if memory is tight, the system will prefer to take memory
from processes that are exceeding their declared resident set size.
.It Li RLIMIT_STACK
The maximum size (in bytes) of the stack segment for a process;
this defines how far a program's stack segment may be extended.
Stack extension is performed automatically by the system.
.El
.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 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 
.Em rlimit
structure is used to specify the hard and soft limits on a resource,
.Bd -literal -offset indent
struct rlimit {
	rlim_t	rlim_cur;	/* current (soft) limit */
	rlim_t	rlim_max;	/* hard limit */
};
.Ed
.Pp
Only the super-user may raise the maximum limits.  Other users
may only alter 
.Fa rlim_cur
within the range from 0 to 
.Fa rlim_max
or (irreversibly) lower
.Fa rlim_max .
.Pp
An
.Dq infinite
value for a limit is defined as
.Dv RLIM_INFINITY .
.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;
.Ic limit
is thus a built-in command to
.Xr csh 1
and
.Ic ulimit
is the
.Xr sh 1
equivalent.
.Pp
The system refuses to extend the data or stack space when the limits
would be exceeded in the normal way: a
.Xr break
call fails if the data space limit is reached.
When the stack limit is reached, the process receives
a segmentation fault
.Pq Dv SIGSEGV ;
if this signal is not
caught by a handler using the signal stack, this signal
will kill the process.
.Pp
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
.Dv SIGXFSZ
to be
generated; this normally terminates the process, but may be caught.  When
the soft cpu time limit is exceeded, a signal
.Dv SIGXCPU
is sent to the
offending 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
.Va errno .
.Sh ERRORS
.Fn Getrlimit
and
.Fn setrlimit
will fail if:
.Bl -tag -width Er
.It Bq Er EFAULT
The address specified for
.Fa rlp
is invalid.
.It Bq Er EPERM
The limit specified to
.Fn setrlimit
would have
raised the maximum limit value, and the caller is not the super-user.
.El
.Sh SEE ALSO
.Xr csh 1 ,
.Xr sh 1 ,
.Xr quota 2 ,
.Xr sigaction 2 ,
.Xr sigaltstack 2 ,
.Xr sysctl 3
.Sh HISTORY
The
.Fn getrlimit
function call appeared in
.Bx 4.2 .
Commit	Line	Data
9bccf70c A	1	.\" $NetBSD: getrlimit.2,v 1.8 1995/10/12 15:40:58 jtc Exp $
	2	.\"
	3	.\" Copyright (c) 1980, 1991, 1993
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)getrlimit.2 8.1 (Berkeley) 6/4/93
	35	.\"
	36	.Dd June 4, 1993
	37	.Dt GETRLIMIT 2
	38	.Os BSD 4
	39	.Sh NAME
	40	.Nm getrlimit ,
	41	.Nm setrlimit
	42	.Nd control maximum system resource consumption
	43	.Sh SYNOPSIS
	44	.Fd #include <sys/types.h>
	45	.Fd #include <sys/time.h>
	46	.Fd #include <sys/resource.h>
	47	.Ft int
	48	.Fn getrlimit "int resource" "struct rlimit *rlp"
	49	.Ft int
	50	.Fn setrlimit "int resource" "const struct rlimit *rlp"
	51	.Sh DESCRIPTION
	52	Limits on the consumption of system resources by the current process
	53	and each process it creates may be obtained with the
	54	.Fn getrlimit
	55	call, and set with the
	56	.Fn setrlimit
	57	call.
	58	.Pp
	59	The
	60	.Fa resource
	61	parameter is one of the following:
	62	.Bl -tag -width RLIMIT_FSIZEAA
	63	.It Li RLIMIT_CORE
	64	The largest size (in bytes)
65	.Xr core
66	file that may be created.
67	.It Li RLIMIT_CPU
68	The maximum amount of cpu time (in seconds) to be used by
69	each process.
70	.It Li RLIMIT_DATA
71	The maximum size (in bytes) of the data segment for a process;
72	this defines how far a program may extend its break with the
73	.Xr sbrk 2
74	system call.
75	.It Li RLIMIT_FSIZE
76	The largest size (in bytes) file that may be created.
77	.It Li RLIMIT_MEMLOCK
78	The maximum size (in bytes) which a process may lock into memory
79	using the
80	.Xr mlock 2
81	function.
82	.It Li RLIMIT_NOFILE
83	The maximum number of open files for this process.
84	.It Li RLIMIT_NPROC
85	The maximum number of simultaneous processes for this user id.
86	.It Li RLIMIT_RSS
87	The maximum size (in bytes) to which a process's resident set size may
88	grow.
89	This imposes a limit on the amount of physical memory to be given to
90	a process; if memory is tight, the system will prefer to take memory
91	from processes that are exceeding their declared resident set size.
92	.It Li RLIMIT_STACK
93	The maximum size (in bytes) of the stack segment for a process;
94	this defines how far a program's stack segment may be extended.
95	Stack extension is performed automatically by the system.
96	.El
97	.Pp
98	A resource limit is specified as a soft limit and a hard limit. When a
99	soft limit is exceeded a process may receive a signal (for example, if
100	the cpu time or file size is exceeded), but it will be allowed to
101	continue execution until it reaches the hard limit (or modifies
102	its resource limit). The
103	.Em rlimit
104	structure is used to specify the hard and soft limits on a resource,
105	.Bd -literal -offset indent
106	struct rlimit {
107	rlim_t rlim_cur; /* current (soft) limit */
108	rlim_t rlim_max; /* hard limit */
109	};
110	.Ed
111	.Pp
112	Only the super-user may raise the maximum limits. Other users
113	may only alter
114	.Fa rlim_cur
115	within the range from 0 to
116	.Fa rlim_max
117	or (irreversibly) lower
118	.Fa rlim_max .
119	.Pp
120	An
121	.Dq infinite
122	value for a limit is defined as
123	.Dv RLIM_INFINITY .
124	.Pp
125	Because this information is stored in the per-process information,
126	this system call must be executed directly by the shell if it
127	is to affect all future processes created by the shell;
128	.Ic limit
129	is thus a built-in command to
130	.Xr csh 1
131	and
132	.Ic ulimit
133	is the
134	.Xr sh 1
135	equivalent.
136	.Pp
137	The system refuses to extend the data or stack space when the limits
138	would be exceeded in the normal way: a
139	.Xr break
140	call fails if the data space limit is reached.
141	When the stack limit is reached, the process receives
142	a segmentation fault
143	.Pq Dv SIGSEGV ;
144	if this signal is not
145	caught by a handler using the signal stack, this signal
146	will kill the process.
147	.Pp
148	A file I/O operation that would create a file larger that the process'
149	soft limit will cause the write to fail and a signal
150	.Dv SIGXFSZ
151	to be
152	generated; this normally terminates the process, but may be caught. When
153	the soft cpu time limit is exceeded, a signal
154	.Dv SIGXCPU
155	is sent to the
156	offending process.
157	.Sh RETURN VALUES
158	A 0 return value indicates that the call succeeded, changing
159	or returning the resource limit. A return value of -1 indicates
160	that an error occurred, and an error code is stored in the global
161	location
162	.Va errno .
163	.Sh ERRORS
164	.Fn Getrlimit
165	and
166	.Fn setrlimit
167	will fail if:
168	.Bl -tag -width Er
169	.It Bq Er EFAULT
170	The address specified for
171	.Fa rlp
172	is invalid.
173	.It Bq Er EPERM
174	The limit specified to
175	.Fn setrlimit
176	would have
177	raised the maximum limit value, and the caller is not the super-user.
178	.El
179	.Sh SEE ALSO
180	.Xr csh 1 ,
181	.Xr sh 1 ,
182	.Xr quota 2 ,
183	.Xr sigaction 2 ,
184	.Xr sigaltstack 2 ,
185	.Xr sysctl 3
186	.Sh HISTORY
187	The
188	.Fn getrlimit
189	function call appeared in
190	.Bx 4.2 .