LIMITS(1) FreeBSD General Commands Manual LIMITS(1)
NAME
limits - set or display process resource limits
SYNOPSIS
limits [-C class | -P pid | -U user] [-SHB] [-ea]
[-bcdfklmnopstuvw [val]]
limits [-C class | -U user] [-SHB] [-bcdfklmnopstuvw [val]] [-E]
[[name=value ...] command]
DESCRIPTION
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. 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. 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.
-P pid Select or set limits for the process identified by the
pid.
-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 in 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.
-k [val] Select or set the kqueues 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.
-o [val] Select or set the umtxp resource limit. The limit
determines the maximal number of the process-shared locks
which may be simultaneously created by the processes
owned by the user, see pthread(3).
-p [val] Select or set the pseudoterminals resource limit.
-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.
-w [val] Select or set the swapuse resource limit.
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.
EXIT STATUS
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.
EXAMPLES
Show current stack size limit:
$ limits -s
Resource limits (current):
stacksize 524288 kB
Try to run ls(1) with 1 byte of datasize limit:
$ limits -d 1b ls
Data segment size exceeds process limit
Abort trap
Produce `eval mode' output to limit sbsize to 1 byte. Output obtained
when command is run from sh(1):
$ limits -e -b 1b
ulimit -b 512;
Same as above from csh(1)
% limits -e -b 1b
limit -h sbsize 512;
limit sbsize 512;
SEE ALSO
csh(1), env(1), limit(1), sh(1), getrlimit(2), setrlimit(2),
login_cap(3), login.conf(5), rctl(8), sysctl(8)
HISTORY
The limits utility first appeared in FreeBSD 2.1.7.
AUTHORS
The limits utility was written by David Nugent <davidn@FreeBSD.org>.
BUGS
The limits utility does not handle commands with equal (`=') signs in
their names, for obvious reasons.
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 13.1-RELEASE-p6 June 25, 2020 FreeBSD 13.1-RELEASE-p6
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