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ulimit(1)

Name | Synopsis | Description | Options | Operands | Examples | Environment Variables | Exit Status | Attributes | See Also

Name

limit, ulimit, unlimit– set or get limitations on the system resources available to the current shell and its descendents

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 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 specifies 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:

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 2⁶⁴.

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 follows:

nh

Hours (for cputime).

nk

n kilobytes. This is the default for all but cputime.

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.

-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 limits. 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.

Per-Shell Memory Parameters

The heapsize, datasize, and stacksize parameters are not system tunables. The only controls for these are hard limits, set in a shell startup file, or system-wide soft limits, which, for the current version of the Solaris OS, is 2⁶⁴bytes.

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 specified, 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 “unlimited” 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
--sbsize

Specifies the socket buffer size in bytes.

-c
--core

Specifies the core file size in blocks.

-d
--data

Specifies the data size in kbytes.

-f
--fsize

Specifies the file size in blocks.

-H

Displays or sets a hard limit.

-L
--locks

Specifies the number of file locks.

-l
--memlock

Specifies the locked address space in Kbytes.

-M
--as

Specifies the address space limit in Kbytes.

-n
--nofile

Specifies the number of open files.

-p
--pipe

Specifies the pipe buffer size in bytes.

-m
--rss

Specifies the resident set size in Kbytes

-S

Displays or sets a soft limit.

-s
--stack

Specifies the stack size in Kbytes.

-T
--threads

Specifies the number of threads.

-t
--cpu

Specifies the CPU time in seconds.

-u
--nproc

Specifies the number of processes.

-v
--vmem

Specifies the process size in Kbytes.

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

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 kilobytes:

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




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, LC_ALL, LC_CTYPE, LC_MESSAGES, 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.

Attributes

See attributes(5) for descriptions of the following attributes:

/usr/bin/ulimit, csh, ksh, sh

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Availability	SUNWcsu
Interface Stability	Committed
Standard	See standards(5).

ksh93

ATTRIBUTE TYPE	ATTRIBUTE 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)

Name | Synopsis | Description | Options | Operands | Examples | Environment Variables | Exit Status | Attributes | See Also