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23 <script language="JavaScript" src="../jscript/codes.js"></script><basefont size="3">
24 <center><font size="2">The Open Group Base Specifications Issue 8<br>
25 IEEE Std 1003.1-2024<br>
26 Copyright © 2001-2024 The IEEE and The Open Group</font></center>
27 <hr size="2" noshade>
28 <a name="top" id="top"></a> <a name="ulimit" id="ulimit"></a> <a name="tag_20_131" id="tag_20_131"></a><!-- ulimit -->
29 <h4 class="mansect"><a name="tag_20_131_01" id="tag_20_131_01"></a>NAME</h4>
30 <blockquote>ulimit — report or set resource limits</blockquote>
31 <h4 class="mansect"><a name="tag_20_131_02" id="tag_20_131_02"></a>SYNOPSIS</h4>
32 <blockquote class="synopsis">
33 <p><code><tt>ulimit</tt> <b>[</b><tt>-H|-S</tt><b>]</b> <tt>-a<br>
34 <br>
35 <sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> ulimit</tt> <b>[</b><tt>-H|-S</tt><b>] [</b><tt>-c|-d|-f|-n|-s|<img src=
36 "../images/opt-start.gif" border="0">-t<img src="../images/opt-end.gif" border="0">|-v</tt><b>] [</b><i>newlimit</i><b>]</b>
37 <tt><br></tt></code></p>
38 </blockquote>
39 <h4 class="mansect"><a name="tag_20_131_03" id="tag_20_131_03"></a>DESCRIPTION</h4>
40 <blockquote>
41 <p>The <i>ulimit</i> utility shall report or set the resource limits in effect in the process in which it is executed.</p>
42 <p>Soft limits can be changed by a process to any value that is less than or equal to the hard limit. A process can (irreversibly)
43 lower its hard limit to any value that is greater than or equal to the soft limit. Only a process with appropriate privileges can
44 raise a hard limit.</p>
45 <p>The value <b>unlimited</b> for a resource shall be considered to be larger than any other limit value. When a resource has this
46 limit value, the implementation shall not enforce limits on that resource. In locales other than the POSIX locale, <i>ulimit</i>
47 may support additional non-numeric values with the same meaning as <b>unlimited</b>.</p>
48 <p>The behavior when resource limits are exceeded shall be as described in the System Interfaces volume of POSIX.1-2024 for the
49 <a href="../functions/setrlimit.html"><i>setrlimit</i>()</a> function.</p>
50 </blockquote>
51 <h4 class="mansect"><a name="tag_20_131_04" id="tag_20_131_04"></a>OPTIONS</h4>
52 <blockquote>
53 <p>The <i>ulimit</i> utility shall conform to XBD <a href="../basedefs/V1_chap12.html#tag_12_02"><i>12.2 Utility Syntax
54 Guidelines</i></a> , except that:</p>
55 <ul>
56 <li>
57 <p>The order in which options other than <b>-H</b>, <b>-S</b>, and <b>-a</b> are specified may be significant.</p>
58 </li>
59 <li>
60 <p>Conforming applications shall specify each option separately; that is, grouping option letters (for example, <b>-fH</b>) need
61 not be recognized by all implementations.</p>
62 </li>
63 </ul>
64 <p>The following options shall be supported:</p>
65 <dl compact>
66 <dd></dd>
67 <dt><b>-H</b></dt>
68 <dd>Report hard limit(s) or set only a hard limit.</dd>
69 <dt><b>-S</b></dt>
70 <dd>Report soft limit(s) or set only a soft limit.</dd>
71 <dt><b>-a</b></dt>
72 <dd>Report the limit value for all of the resources named below and for any implementation-specific additional resources.</dd>
73 <dt><b>-c</b></dt>
74 <dd>Report, or set if the <i>newlimit</i> operand is present, the core image size limit(s) in units of 512 bytes.
75 [RLIMIT_CORE]</dd>
76 <dt><b>-d</b></dt>
77 <dd>Report, or set if the <i>newlimit</i> operand is present, the data segment size limit(s) in units of 1024 bytes.
78 [RLIMIT_DATA]</dd>
79 <dt><b>-f</b></dt>
80 <dd>Report, or set if the <i>newlimit</i> operand is present, the file size limit(s) in units of 512 bytes. [RLIMIT_FSIZE]</dd>
81 <dt><b>-n</b></dt>
82 <dd>Report, or set if the <i>newlimit</i> operand is present, the limit(s) on the number of open file descriptors, given as a
83 number one greater than the maximum value that the system assigns to a newly-created descriptor. [RLIMIT_NOFILE]</dd>
84 <dt><b>-s</b></dt>
85 <dd>Report, or set if the <i>newlimit</i> operand is present, the stack size limit(s) in units of 1024 bytes. [RLIMIT_STACK]</dd>
86 <dt><b>-t</b></dt>
87 <dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
88 Report, or set if the <i>newlimit</i> operand is present, the per-process CPU time limit(s) in units of seconds. [RLIMIT_CPU]
89 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
90 <dt><b>-v</b></dt>
91 <dd>Report, or set if the <i>newlimit</i> operand is present, the address space size limit(s) in units of 1024 bytes.
92 [RLIMIT_AS]</dd>
93 </dl>
94 <p>Where an option description is followed by [RLIMIT_<i>name</i>] it indicates which resource for the <a href=
95 "../functions/getrlimit.html"><i>getrlimit</i>()</a> and <a href="../functions/setrlimit.html"><i>setrlimit</i>()</a> functions,
96 defined in the System Interfaces volume of POSIX.1-2024, the option corresponds to.</p>
97 <p>If neither the <b>-H</b> nor <b>-S</b> option is specified:</p>
98 <ul>
99 <li>
100 <p>If the <i>newlimit</i> operand is present, it shall be used as the new value for both the hard and soft limits.</p>
101 </li>
102 <li>
103 <p>If the <i>newlimit</i> operand is not present, <b>-S</b> shall be the default.</p>
104 </li>
105 </ul>
106 <p>If no options other than <b>-H</b> or <b>-S</b> are specified, the behavior shall be as if the <b>-f</b> option was (also)
107 specified.</p>
108 <p>If any option other than <b>-H</b> or <b>-S</b> is repeated, the behavior is unspecified.</p>
109 </blockquote>
110 <h4 class="mansect"><a name="tag_20_131_05" id="tag_20_131_05"></a>OPERANDS</h4>
111 <blockquote>
112 <p>The following operand shall be supported:</p>
113 <dl compact>
114 <dd></dd>
115 <dt><i>newlimit</i></dt>
116 <dd>Either an integer value to use as the new limit(s) for the specified resource, in the units specified in OPTIONS, or a
117 non-numeric string indicating no limit, as described in the DESCRIPTION section. Numerals in the range 0 to the maximum limit value
118 supported by the implementation for any resource shall be syntactically recognized as numeric values.</dd>
119 </dl>
120 </blockquote>
121 <h4 class="mansect"><a name="tag_20_131_06" id="tag_20_131_06"></a>STDIN</h4>
122 <blockquote>
123 <p>Not used.</p>
124 </blockquote>
125 <h4 class="mansect"><a name="tag_20_131_07" id="tag_20_131_07"></a>INPUT FILES</h4>
126 <blockquote>
127 <p>None.</p>
128 </blockquote>
129 <h4 class="mansect"><a name="tag_20_131_08" id="tag_20_131_08"></a>ENVIRONMENT VARIABLES</h4>
130 <blockquote>
131 <p>The following environment variables shall affect the execution of <i>ulimit</i>:</p>
132 <dl compact>
133 <dd></dd>
134 <dt><i>LANG</i></dt>
135 <dd>Provide a default value for the internationalization variables that are unset or null. (See XBD <a href=
136 "../basedefs/V1_chap08.html#tag_08_02"><i>8.2 Internationalization Variables</i></a> for the precedence of internationalization
137 variables used to determine the values of locale categories.)</dd>
138 <dt><i>LC_ALL</i></dt>
139 <dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd>
140 <dt><i>LC_CTYPE</i></dt>
141 <dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as
142 opposed to multi-byte characters in arguments).</dd>
143 <dt><i>LC_MESSAGES</i></dt>
144 <dd><br>
145 Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.</dd>
146 <dt><i>NLSPATH</i></dt>
147 <dd>Determine the location of messages objects and message catalogs.</dd>
148 </dl>
149 </blockquote>
150 <h4 class="mansect"><a name="tag_20_131_09" id="tag_20_131_09"></a>ASYNCHRONOUS EVENTS</h4>
151 <blockquote>
152 <p>Default.</p>
153 </blockquote>
154 <h4 class="mansect"><a name="tag_20_131_10" id="tag_20_131_10"></a>STDOUT</h4>
155 <blockquote>
156 <p>The standard output shall be used when no <i>newlimit</i> operand is present.</p>
157 <p>If the <b>-a</b> option is specified, the output written for each resource shall consist of one line that includes:</p>
158 <ul>
159 <li>
160 <p>A short phrase identifying the resource (for example "file size").</p>
161 </li>
162 <li>
163 <p>An indication of the units used for the resource, if the corresponding option description in OPTIONS specifies the units to be
164 used.</p>
165 </li>
166 <li>
167 <p>The <i>ulimit</i> option used to specify the resource.</p>
168 </li>
169 <li>
170 <p>The limit value.</p>
171 </li>
172 </ul>
173 <p>The format used within each line is unspecified, except that the format used for the limit value shall be as described below for
174 the case where a single limit value is written.</p>
175 <p>If a single limit value is to be written; that is, the <b>-a</b> option is not specified and at most one option other than
176 <b>-H</b> or <b>-S</b> is specified:</p>
177 <ul>
178 <li>
179 <p>If the resource being reported has a numeric limit, the limit value shall be written in the following format:</p>
180 <pre>
181 <tt>"%1d\n", <</tt><i>limit value</i><tt>>
182 </tt></pre>
183 <p>where <<i>limit value</i>> is the value of the limit in the units specified in OPTIONS.</p>
184 </li>
185 <li>
186 <p>If the resource being reported does not have a numeric limit, in the POSIX locale the following format shall be used:</p>
187 <pre>
188 <tt>"unlimited\n"
189 </tt></pre></li>
190 </ul>
191 </blockquote>
192 <h4 class="mansect"><a name="tag_20_131_11" id="tag_20_131_11"></a>STDERR</h4>
193 <blockquote>
194 <p>The standard error shall be used only for diagnostic messages.</p>
195 </blockquote>
196 <h4 class="mansect"><a name="tag_20_131_12" id="tag_20_131_12"></a>OUTPUT FILES</h4>
197 <blockquote>
198 <p>None.</p>
199 </blockquote>
200 <h4 class="mansect"><a name="tag_20_131_13" id="tag_20_131_13"></a>EXTENDED DESCRIPTION</h4>
201 <blockquote>
202 <p>None.</p>
203 </blockquote>
204 <h4 class="mansect"><a name="tag_20_131_14" id="tag_20_131_14"></a>EXIT STATUS</h4>
205 <blockquote>
206 <p>The following exit values shall be returned:</p>
207 <dl compact>
208 <dd></dd>
209 <dt> 0</dt>
210 <dd>Successful completion.</dd>
211 <dt>>0</dt>
212 <dd>A request for a higher limit was rejected or an error occurred.</dd>
213 </dl>
214 </blockquote>
215 <h4 class="mansect"><a name="tag_20_131_15" id="tag_20_131_15"></a>CONSEQUENCES OF ERRORS</h4>
216 <blockquote>
217 <p>Default.</p>
218 </blockquote>
219 <hr>
220 <div class="box"><em>The following sections are informative.</em></div>
221 <h4 class="mansect"><a name="tag_20_131_16" id="tag_20_131_16"></a>APPLICATION USAGE</h4>
222 <blockquote>
223 <p>This utility is required to be intrinsic. See <a href="../utilities/V3_chap01.html#tag_18_07"><i>1.7 Intrinsic Utilities</i></a>
224 for details.</p>
225 <p>Since <i>ulimit</i> affects the current shell execution environment, it is always provided as a shell regular built-in. If it is
226 called with an operand in a separate utility execution environment, such as one of the following:</p>
227 <pre>
228 <tt>nohup ulimit -f 10000
229 env ulimit -S -c 10000
230 </tt></pre>
231 <p>it does not affect the limit(s) in the caller's environment.</p>
232 <p>See also the APPLICATION USAGE for <a href="../functions/getrlimit.html#"><i>getrlimit</i></a> .</p>
233 </blockquote>
234 <h4 class="mansect"><a name="tag_20_131_17" id="tag_20_131_17"></a>EXAMPLES</h4>
235 <blockquote>
236 <p>Set the hard and soft file size limits to 51200 bytes:</p>
237 <pre>
238 <tt>ulimit -f 100
239 </tt></pre>
240 <p>Save and restore a soft resource limit (where <i>X</i> is an option letter specifying a resource):</p>
241 <pre>
242 <tt>saved=$(ulimit -</tt><i>X</i><tt>)
243
244 ...
245
246 ulimit -</tt><i>X</i><tt> -S "$saved"
247 </tt></pre>
248 <p>Execute a utility with a CPU limit of 5 minutes (using an asynchronous subshell to ensure the limit is set in a child
249 process):</p>
250 <pre>
251 <tt>(ulimit -t 300; exec utility_name </dev/null) &
252 wait $!
253 </tt></pre></blockquote>
254 <h4 class="mansect"><a name="tag_20_131_18" id="tag_20_131_18"></a>RATIONALE</h4>
255 <blockquote>
256 <p>The <i>ulimit</i> utility has no equivalent of the special values RLIM_SAVED_MAX and RLIM_SAVED_CUR returned by <a href=
257 "../functions/getrlimit.html"><i>getrlimit</i>()</a>, as <i>ulimit</i> is required to be able to output, and accept as input, all
258 numeric limit values supported by the system.</p>
259 <p>Implementations differ in their behavior when the <b>-a</b> option is not specified and more than one option other than
260 <b>-H</b> or <b>-S</b> is specified. Some write output for all of the specified resources in the same format as for <b>-a</b>;
261 others write only the value for the last specified option. Both behaviors are allowed by the standard, since the SYNOPSIS lists the
262 options as mutually exclusive.</p>
263 </blockquote>
264 <h4 class="mansect"><a name="tag_20_131_19" id="tag_20_131_19"></a>FUTURE DIRECTIONS</h4>
265 <blockquote>
266 <p>None.</p>
267 </blockquote>
268 <h4 class="mansect"><a name="tag_20_131_20" id="tag_20_131_20"></a>SEE ALSO</h4>
269 <blockquote>
270 <p>XBD <a href="../basedefs/V1_chap08.html#tag_08"><i>8. Environment Variables</i></a> , <a href=
271 "../basedefs/V1_chap12.html#tag_12_02"><i>12.2 Utility Syntax Guidelines</i></a></p>
272 <p>XSH <a href="../functions/getrlimit.html#"><i>getrlimit</i></a></p>
273 </blockquote>
274 <h4 class="mansect"><a name="tag_20_131_21" id="tag_20_131_21"></a>CHANGE HISTORY</h4>
275 <blockquote>
276 <p>First released in Issue 2.</p>
277 </blockquote>
278 <h4 class="mansect"><a name="tag_20_131_22" id="tag_20_131_22"></a>Issue 7</h4>
279 <blockquote>
280 <p>SD5-XCU-ERN-97 is applied, updating the SYNOPSIS.</p>
281 </blockquote>
282 <h4 class="mansect"><a name="tag_20_131_23" id="tag_20_131_23"></a>Issue 8</h4>
283 <blockquote>
284 <p>Austin Group Defect 854 is applied, adding a note to the APPLICATION USAGE section that this utility is required to be
285 intrinsic.</p>
286 <p>Austin Group Defect 1122 is applied, changing the description of <i>NLSPATH .</i></p>
287 <p>Austin Group Defect 1418 is applied, adding the <b>-H</b>, <b>-S</b>, <b>-a</b>, <b>-c</b>, <b>-d</b>, <b>-n</b>, <b>-s</b>,
288 <b>-t</b>, and <b>-v</b> options, and relating the <b>-f</b> option to the RLIMIT_FSIZE resource for <a href=
289 "../functions/setrlimit.html"><i>setrlimit</i>()</a>.</p>
290 <p>Austin Group Defect 1669 is applied, moving the <i>ulimit</i> utility, excluding the <b>-t</b> option, from the XSI option to
291 the Base.</p>
292 </blockquote>
293 <div class="box"><em>End of informative text.</em></div>
294 <hr>
295 <p> </p>
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