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]
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 may 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 may be printed at one time. The -a
option prints all limits.
If limit is present, ulimit sets the specified limit to
limit. The string unlimited requests the largest valid
limit. Limits may be set for only one resource at a time.
Any user may set a soft limit to any value below the hard
limit. Any user may lower a hard limit. Only a super-user
may raise a hard limit; see su(1M).
The -H option specifies a hard limit. The -S option speci-
fies a soft limit. If neither option is specified, ulimit
will set both limits and print 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. If limit is omitted,
print the current limit; if resource is omitted, display all
limits. (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).
-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 may 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 (see swap(1M)).
coredumpsize
Maximum size of a core dump (file). This is limited to
the size of the filesystem.
descriptors
Maximum number of file descriptors (run sysdef()).
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 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 may 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 -H and -S flags specify whether the hard limit or the
soft limit for the given resource is set. A hard limit can-
not 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 speci-
fied. 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 may 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 given, -f is assumed.
OPTIONS
The following option is supported by ulimit:
-f Set (or report, 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 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
To limit 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
To limit 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
To limit 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
To remove 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 attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
| Interface Stability | Standard |
|_____________________________|_____________________________|
SEE ALSO
bc(1), csh(1), ksh(1), sh(1), df(1M), su(1M), swap(1M),
sysdef(1M), getrlimit(2), attributes(5), environ(5), stan-
dards(5)
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