User Commands limit(1)
NAME
limit, ulimit, unlimit - set or get limitations on the sys-
tem resources available to the current shell and its descen-
dents
SYNOPSIS
/usr/bin/ulimit [-f] [blocks]
sh
ulimit [- [HS] [a cdfnstv]
ulimit [- [HS] [c d f n s t v] limit
csh
limit [-h] [resource [limit]
unlimit [-h] [resource]
ksh
ulimit [-HSacdfnstv] [limit]
ksh93
ulimit [-HSacdfmnpstv] [limit]
DESCRIPTION
/usr/bin/ulimit
The ulimit utility sets or reports the file-size writing
limit imposed on files written by the shell and its child
processes (files of any size can be read). Only a process
with appropriate privileges can increase the limit.
sh
The Bourne shell built-in function, ulimit, prints or sets
hard or soft resource limits. These limits are described in
getrlimit(2).
If limit is not present, ulimit prints the specified limits.
Any number of limits can be printed at one time. The -a
option prints all limits.
If limit is present, ulimit sets the specified limit
tolimit. The string unlimited requests that the current
limit, if any, be removed. Any user can set a soft limit to
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User Commands limit(1)
any value less than or equal to the hard limit. Any user can
lower a hard limit. Only a user with appropriate privileges
can raise or remove a hard limit. See getrlimit(2).
The -H option specifies a hard limit. The -S option speci-
fies a soft limit. If neither option is specified, ulimit
sets both limits and prints the soft limit.
The following options specify the resource whose limits are
to be printed or set. If no option is specified, the file
size limit is printed or set.
-c Maximum core file size (in 512-byte blocks)
-d Maximum size of data segment or heap (in Kbytes)
-f Maximum file size (in 512-byte blocks)
-n Maximum file descriptor plus 1
-s Maximum size of stack segment (in Kbytes)
-t Maximum CPU time (in seconds)
-v Maximum size of virtual memory (in Kbytes)
csh
The C-shell built-in function, limit, limits the consumption
by the current process or any process it spawns, each not to
exceed limit on the specified resource. The string unlimited
requests that the current limit, if any, be removed. If
limit is omitted, prints the current limit. If resource is
omitted, displays all limits.
-h Use hard limits instead of the current limits. Hard
limits impose a ceiling on the values of the current
limits. Only the privileged user can raise the hard
limits.
resource is one of:
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User Commands limit(1)
cputime Maximum CPU seconds per process.
filesize Largest single file allowed. Limited to the
size of the filesystem (see df(1M)).
datasize The maximum size of a process's heap in
kilobytes.
stacksize Maximum stack size for the process. The
default stack size is 2^64.
coredumpsize Maximum size of a core dump (file). This is
limited to the size of the filesystem.
descriptors Maximum number of file descriptors. Run the
sysdef(1M) command to obtain the maximum
possible limits for your system. The values
reported are in hexadecimal, but can be
translated into decimal numbers using the
bc(1) command.
memorysize Maximum size of virtual memory.
limit is a number, with an optional scaling factor, as fol-
lows:
nh Hours (for cputime).
nk n kilobytes. This is the default for all but cpu-
time.
nm n megabytes or minutes (for cputime).
mm:ss Minutes and seconds (for cputime).
unlimit removes a limitation on resource. If no resource is
specified, then all resource limitations are removed. See
the description of the limit command for the list of
resource names.
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User Commands limit(1)
-h Remove corresponding hard limits. Only the privileged
user can do this.
ksh
The Korn shell built-in function, ulimit, sets or displays a
resource limit. The available resources limits are listed
below. Many systems do not contain one or more of these lim-
its. The limit for a specified resource is set when limit is
specified. The value of limit can be a number in the unit
specified below with each resource, or the value unlimited.
The string unlimited requests that the current limit, if
any, be removed. The -H and -S flags specify whether the
hard limit or the soft limit for the specified resource is
set. A hard limit cannot be increased once it is set. A soft
limit can be increased up to the value of the hard limit. If
neither the -H or -S options is specified, the limit applies
to both. The current resource limit is printed when limit is
omitted. In this case, the soft limit is printed unless -H
is specified. When more than one resource is specified, then
the limit name and unit is printed before the value.
-a Lists all of the current resource limits.
-c The number of 512-byte blocks on the size of core
dumps.
-d The number of K-bytes on the size of the data area.
-f The number of 512-byte blocks on files written by
child processes (files of any size can be read).
-n The number of file descriptors plus 1.
-s The number of K-bytes on the size of the stack area.
-t The number of seconds (CPU time) to be used by each
process.
-v The number of K-bytes for virtual memory.
If no option is specified, -f is assumed.
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User Commands limit(1)
Per-Shell Memory Parameters
The heapsize, datasize, and stacksize parameters are not
system tunables. The only controls for these are hard lim-
its, set in a shell startup file, or system-wide soft lim-
its, which, for the current version of the Solaris OS, is
2^64bytes.
ksh93
ulimit sets or displays resource limits. These limits apply
to the current process and to each child process created
after the resource limit has been set. If limit is speci-
fied, the resource limit is set, otherwise, its current
value is displayed on standard output.
Increasing the limit for a resource usually requires special
privileges. Some systems allow you to lower resource limits
and later increase them. These are called soft limits. Once
a hard limit is set the resource cannot be increased.
Different systems allow you to specify different resources
and some restrict how much you can raise the limit of the
resource.
The value of limit depends on the unit of the resource
listed for each resource. In addition, limit can be "unlim-
ited" to indicate no limit for that resource.
If you do not specify -H or -S, -S is used for listing and
both -S and -H are used for setting resources.
If you do not specify any resource, the default is -f.
The following options are available for ulimit in ksh93:
-a Displays all current resource limits.
-b Specifies the socket buffer size in bytes.
--sbsize
-c Specifies the core file size in blocks.
--core
-d Specifies the data size in kbytes.
--data
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User Commands limit(1)
-f Specifies the file size in blocks.
--fsize
-H Displays or sets a hard limit.
-L Specifies the number of file locks.
--locks
-l Specifies the locked address space in Kbytes.
--memlock
-M Specifies the address space limit in Kbytes.
--as
-n Specifies the number of open files.
--nofile
-p Specifies the pipe buffer size in bytes.
--pipe
-m Specifies the resident set size in Kbytes
--rss
-S Displays or sets a soft limit.
-s Specifies the stack size in Kbytes.
--stack
-T Specifies the number of threads.
--threads
-t Specifies the CPU time in seconds.
--cpu
-u Specifies the number of processes.
--nproc
-v Specifies the process size in Kbytes.
--vmem
OPTIONS
The following option is supported by /usr/bin/ulimit:
-f Sets (or reports, if no blocks operand is present),
the file size limit in blocks. The -f option is also
the default case.
OPERANDS
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User Commands limit(1)
The following operand is supported by /usr/bin/ulimit:
blocks The number of 512-byte blocks to use as the new
file size limit.
EXAMPLES
/usr/bin/ulimit
Example 1 Limiting the Stack Size
The following example limits the stack size to 512 kilo-
bytes:
example% ulimit -s 512
example% ulimit -a
time(seconds) unlimited
file(blocks) 100
data(kbytes) 523256
stack(kbytes) 512
coredump(blocks) 200
nofiles(descriptors) 64
memory(kbytes) unlimited
sh/ksh
Example 2 Limiting the Number of File Descriptors
The following command limits the number of file descriptors
to 12:
example$ ulimit -n 12
example$ ulimit -a
time(seconds) unlimited
file(blocks) 41943
data(kbytes) 523256
stack(kbytes) 8192
coredump(blocks) 200
nofiles(descriptors) 12
vmemory(kbytes) unlimited
csh
Example 3 Limiting the Core Dump File Size
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User Commands limit(1)
The following command limits the size of a core dump file
size to 0 kilobytes:
example% limit coredumpsize 0
example% limit
cputime unlimited
filesize unlimited
datasize 523256 kbytes
stacksize 8192 kbytes
coredumpsize 0 kbytes
descriptors 64
memorysize unlimited
Example 4 Removing the limitation for core file size
The following command removes the above limitation for the
core file size:
example% unlimit coredumpsize
example% limit
cputime unlimited
filesize unlimited
datasize 523256 kbytes
stacksize 8192 kbytes
coredumpsize unlimited
descriptors 64
memorysize unlimited
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment
variables that affect the execution of ulimit: LANG, LCAL,
LCTYPE, LCMESAGES, and NLSPATH.
EXIT STATUS
The following exit values are returned by ulimit:
0 Successful completion.
>0 A request for a higher limit was rejected or an error
occurred.
ATRIBUTES
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User Commands limit(1)
See attributes(5) for descriptions of the following attri-
butes:
/usr/bin/ulimit, csh, ksh, sh
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWcsu
Interface Stability Committed
Standard See standards(5).
ksh93
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWcsu
Interface Stability Uncommitted
SEE ALSO
bc(1), csh(1), ksh(1), ksh93(1), sh(1), df(1M), su(1M),
swap(1M), sysdef(1M), getrlimit(2), attributes(5),
environ(5), standards(5)
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