limits -- set or display process resource limits
limits [-C class | -U user] [-SHB] [-ea] [-bcdflmnstuv [val]]
limits [-C class | -U user] [-SHB] [-bcdflmnstuv [val]] [-E]
[[name=value ...] command]
The limits utility either prints or sets kernel resource limits, and may
optionally set environment variables like env(1) and run a program with
the selected resources. Three uses of the limits utility are possible:
limits [limitflags] [name=value ...] command
This usage sets limits according to limitflags, optionally sets
environment variables given as name=value pairs, and then runs
the specified command.
limits [limitflags]
This usage determines values of resource settings according to
limitflags, does not attempt to set them and outputs these values
to standard output. By default, this will output the current
kernel resource settings active for the calling process. Using
the -C class or -U user options, you may also display the current
resource settings modified by the appropriate login class
resource limit entries from the login.conf(5) login capabilities
database.
limits -e [limitflags]
This usage determines values of resource settings according to
limitflags, but does not set them itself. Like the previous
usage, it outputs these values to standard output, except that it
will emit them in eval format, suitable for the calling shell.
The calling shell is determined by examining the entries in the
/proc file system for the parent process. If the shell is known
(i.e. it is one of sh, csh, bash, tcsh, ksh, pdksh or rc), limits
emits limit or ulimit commands in the format understood by that
shell. If the name of the shell cannot be determined, then the
ulimit format used by sh(1) is used.
This is very useful for setting limits used by scripts, or prior
launching of daemons and other background tasks with specific
resource limit settings, and provides the benefit of allowing
global configuration of maximum resource usage by maintaining a
central database of settings in the login class database.
Within a shell script, limits will normally be used with eval
within backticks as follows:
eval `limits -e -C daemon`
which causes the output of limits to be evaluated and set by the
current shell.
The value of limitflags specified in the above contains one or more of
the following options:
-C class Use current resource values, modified by the resource entries
applicable for the login class class.
-U user Use current resource values, modified by the resource entries
applicable to the login class the user belongs to. If user
does not belong to any class, then the resource capabilities
for the ``default'' class are used, if it exists, or the
``root'' class if the user is a superuser account.
-S Select display or setting of ``soft'' (or current) resource
limits. If specific limits settings follow this switch, only
soft limits are affected unless overridden later with either
the -H or -B options.
-H Select display or setting of ``hard'' (or maximum) resource
limits. If specific limits settings follow this switch, only
hard limits are affected until overridden later with either the
-S or -B options.
-B Select display or setting of both ``soft'' (current) or
``hard'' (maximum) resource limits. If specific limits settings
follow this switch, both soft and hard limits are
affected until overridden later with either the -S or -H
options. -e Select ``eval mode'' formatting for output. This
is valid only on display mode and cannot be used when running a
command. The exact syntax used for output depends upon the
type of shell from which limits is invoked.
-b [val] Select or set the sbsize resource limit.
-c [val] Select or set (if val is specified) the coredumpsize resource
limit. A value of 0 disables core dumps.
-d [val] Select or set (if val is specified) the datasize resource
limit.
-f [val] Select or set the filesize resource limit.
-l [val] Select or set the memorylocked resource limit.
-m [val] Select or set the memoryuse size limit.
-n [val] Select or set the openfiles resource limit. The system-wide
limit on the maximum number of open files per process can be
viewed by examining the kern.maxfilesperproc sysctl(8) variable.
The total number of simultaneously open files in the
entire system is limited to the value displayed by the
kern.maxfiles sysctl(8) variable.
-s [val] Select or set the stacksize resource limit.
-t [val] Select or set the cputime resource limit.
-u [val] Select or set the maxproc resource limit. The system-wide
limit on the maximum number of processes allowed per UID can be
viewed by examining the kern.maxprocperuid sysctl(8) variable.
The maximum number of processes that can be running simultaneously
in the entire system is limited to the value of the
kern.maxproc sysctl(8) variable.
-v [val] Select or set the virtualmem resource limit. This limit encompasses
the entire VM space for the user process and is inclusive
of text, data, bss, stack, brk(2), sbrk(2) and mmap(2)'d
space.
Valid values for val in the above set of options consist of either the
string ``infinity'', ``inf'', ``unlimited'' or ``unlimit'' for an infinite
(or kernel-defined maximum) limit, or a numeric value optionally
followed by a suffix. Values which relate to size default to a value in
bytes, or one of the following suffixes may be used as a multiplier:
b 512 byte blocks.
k kilobytes (1024 bytes).
m megabytes (1024*1024 bytes).
g gigabytes.
t terabytes.
The cputime resource defaults to a number of seconds, but a multiplier
may be used, and as with size values, multiple values separated by a
valid suffix are added together:
s seconds.
m minutes.
h hours.
d days.
w weeks.
y 365 day years.
-E Cause limits to completely ignore the environment it inherits.
-a Force all resource settings to be displayed even if other specific
resource settings have been specified. For example, if
you wish to disable core dumps when starting up the Usenet News
system, but wish to set all other resource settings as well
that apply to the ``news'' account, you might use:
eval `limits -U news -aBec 0`
As with the setrlimit(2) call, only the superuser may raise
process ``hard'' resource limits. Non-root users may, however,
lower them or change ``soft'' resource limits within to any
value below the hard limit. When invoked to execute a program,
the failure of limits to raise a hard limit is considered a
fatal error.
The limits utility exits with EXIT_FAILURE if usage is incorrect in any
way; i.e. an invalid option, or set/display options are selected in the
same invocation, -e is used when running a program, etc. When run in
display or eval mode, limits exits with a status of EXIT_SUCCESS. When
run in command mode and execution of the command succeeds, the exit status
will be whatever the executed program returns.
csh(1), env(1), limit(1), sh(1), getrlimit(2), setrlimit(2),
login_cap(3), login.conf(5), sysctl(8)
The limits utility does not handle commands with equal (`=') signs in
their names, for obvious reasons.
When eval output is selected, the /proc file system must be installed and
mounted for the shell to be correctly determined, and therefore output
syntax correct for the running shell. The default output is valid for
sh(1), so this means that any usage of limits in eval mode prior mounting
/proc may only occur in standard bourne shell scripts.
The limits utility makes no effort to ensure that resource settings emitted
or displayed are valid and settable by the current user. Only a
superuser account may raise hard limits, and when doing so the FreeBSD
kernel will silently lower limits to values less than specified if the
values given are too high.
FreeBSD 5.2.1 September 18, 2002 FreeBSD 5.2.1 [ Back ] |
