363 lines
13 KiB
HTML
363 lines
13 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>df</title>
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<basefont size="3"> <a name="df"></a> <a name="tag_04_36"></a><!-- df -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_04_36_01"></a>NAME</h4>
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<blockquote>df - report free disk space</blockquote>
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<h4><a name="tag_04_36_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('UP XSI')">UP XSI</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> df</tt> <b>[</b><tt>-k</tt><b>][</b><tt>-P|-t</tt><b>][</b><i>file</i><tt>...</tt><b>]</b><tt><img
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src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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</blockquote>
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<h4><a name="tag_04_36_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>df</i> utility shall write the amount of available space <sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img
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src="../images/opt-start.gif" alt="[Option Start]" border="0"> and file slots <img src="../images/opt-end.gif" alt=
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"[Option End]" border="0"> for file systems on which the invoking user has appropriate read access. File systems shall be specified
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by the <i>file</i> operands; when none are specified, information shall be written for all file systems. The format of the default
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output from <i>df</i> is unspecified, but all space figures are reported in 512-byte units, unless the <b>-k</b> option is
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specified. This output shall contain at least the file system names, amount of available space on each of these file systems,
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<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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and the number of free file slots, or <i>inodes</i>, available; when <b>-t</b> is specified, the output shall contain the
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total allocated space as well. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_04_36_04"></a>OPTIONS</h4>
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<blockquote>
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<p>The <i>df</i> utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/xbd_chap12.html#tag_12_02">Section 12.2, Utility Syntax Guidelines</a>.</p>
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<p>The following options shall be supported:</p>
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<dl compact>
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<dt><b>-k</b></dt>
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<dd>Use 1024-byte units, instead of the default 512-byte units, when writing space figures.</dd>
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<dt><b>-P</b></dt>
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<dd>Produce output in the format described in the STDOUT section.</dd>
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<dt><b>-t</b></dt>
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<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Include total allocated-space figures in the output. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_36_05"></a>OPERANDS</h4>
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<blockquote>
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<p>The following operand shall be supported:</p>
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<dl compact>
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<dt><i>file</i></dt>
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<dd>A pathname of a file within the hierarchy of the desired file system. If a file other than a FIFO, a regular file, a directory,
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<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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or a special file representing the device containing the file system (for example, <b>/dev/dsk/0s1</b>) <img src=
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"../images/opt-end.gif" alt="[Option End]" border="0"> is specified, the results are unspecified. Otherwise, <i>df</i> shall write
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the amount of free space in the file system containing the specified <i>file</i> operand.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_36_06"></a>STDIN</h4>
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<blockquote>
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<p>Not used.</p>
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</blockquote>
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<h4><a name="tag_04_36_07"></a>INPUT FILES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_36_08"></a>ENVIRONMENT VARIABLES</h4>
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<blockquote>
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<p>The following environment variables shall affect the execution of <i>df</i>:</p>
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<dl compact>
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<dt><i>LANG</i></dt>
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<dd>Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html#tag_08_02">Section 8.2, Internationalization Variables</a> for
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the precedence of internationalization variables used to determine the values of locale categories.)</dd>
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<dt><i>LC_ALL</i></dt>
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<dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd>
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<dt><i>LC_CTYPE</i></dt>
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<dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as
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opposed to multi-byte characters in arguments).</dd>
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<dt><i>LC_MESSAGES</i></dt>
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<dd>Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error and
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informative messages written to standard output.</dd>
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<dt><i>NLSPATH</i></dt>
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<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Determine the location of message catalogs for the processing of <i>LC_MESSAGES .</i> <img src="../images/opt-end.gif" alt=
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"[Option End]" border="0"></dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_36_09"></a>ASYNCHRONOUS EVENTS</h4>
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<blockquote>
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<p>Default.</p>
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</blockquote>
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<h4><a name="tag_04_36_10"></a>STDOUT</h4>
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<blockquote>
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<p>When both the <b>-k</b> and <b>-P</b> options are specified, the following header line shall be written (in the POSIX
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locale):</p>
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<pre>
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<tt>"Filesystem 1024-blocks Used Available Capacity Mounted on\n"
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</tt>
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</pre>
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<p>When the <b>-P</b> option is specified without the <b>-k</b> option, the following header line shall be written (in the POSIX
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locale):</p>
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<pre>
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<tt>"Filesystem 512-blocks Used Available Capacity Mounted on\n"
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</tt>
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</pre>
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<p>The implementation may adjust the spacing of the header line and the individual data lines so that the information is presented
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in orderly columns.</p>
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<p>The remaining output with <b>-P</b> shall consist of one line of information for each specified file system. These lines shall
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be formatted as follows:</p>
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<pre>
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<tt>"%s %d %d %d %d%% %s\n", <</tt><i>file system name</i><tt>>, <</tt><i>total space</i><tt>>,
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<</tt><i>space used</i><tt>>, <</tt><i>space free</i><tt>>, <</tt><i>percentage used</i><tt>>,
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<</tt><i>file system root</i><tt>>
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</tt>
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</pre>
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<p>In the following list, all quantities expressed in 512-byte units (1024-byte when <b>-k</b> is specified) shall be rounded up to
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the next higher unit. The fields are:</p>
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<dl compact>
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<dt><<i>file system name</i>></dt>
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<dd><br>
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The name of the file system, in an implementation-defined format.</dd>
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<dt><<i>total space</i>></dt>
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<dd>The total size of the file system in 512-byte units. The exact meaning of this figure is implementation-defined, but should
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include <<i>space used</i>>, <<i>space free</i>>, plus any space reserved by the system not normally
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available to a user.</dd>
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<dt><<i>space used</i>></dt>
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<dd>The total amount of space allocated to existing files in the file system, in 512-byte units.</dd>
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<dt><<i>space free</i>></dt>
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<dd>The total amount of space available within the file system for the creation of new files by unprivileged users, in 512-byte
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units. When this figure is less than or equal to zero, it shall not be possible to create any new files on the file system without
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first deleting others, unless the process has appropriate privileges. The figure written may be less than zero.</dd>
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<dt><<i>percentage used</i>></dt>
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<dd><br>
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The percentage of the normally available space that is currently allocated to all files on the file system. This shall be
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calculated using the fraction:
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<pre>
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<tt><</tt><i>space used</i><tt>>/( <</tt><i>space used</i><tt>>+ <</tt><i>space free</i><tt>>)
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</tt>
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</pre>
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<p>expressed as a percentage. This percentage may be greater than 100 if <<i>space free</i>> is less than zero. The
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percentage value shall be expressed as a positive integer, with any fractional result causing it to be rounded to the next highest
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integer.</p>
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</dd>
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<dt><<i>file system root</i>></dt>
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<dd><br>
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The directory below which the file system hierarchy appears.</dd>
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</dl>
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<p><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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The output format is unspecified when <b>-t</b> is used. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_04_36_11"></a>STDERR</h4>
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<blockquote>
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<p>The standard error shall be used only for diagnostic messages.</p>
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</blockquote>
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<h4><a name="tag_04_36_12"></a>OUTPUT FILES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_36_13"></a>EXTENDED DESCRIPTION</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_36_14"></a>EXIT STATUS</h4>
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<blockquote>
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<p>The following exit values shall be returned:</p>
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<dl compact>
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<dt> 0</dt>
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<dd>Successful completion.</dd>
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<dt>>0</dt>
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<dd>An error occurred.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_36_15"></a>CONSEQUENCES OF ERRORS</h4>
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<blockquote>
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<p>Default.</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_04_36_16"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>On most systems, the "name of the file system, in an implementation-defined format" is the special file on which the file
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system is mounted.</p>
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<p>On large file systems, the calculation specified for percentage used can create huge rounding errors.</p>
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</blockquote>
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<h4><a name="tag_04_36_17"></a>EXAMPLES</h4>
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<blockquote>
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<ol>
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<li>
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<p>The following example writes portable information about the <b>/usr</b> file system:</p>
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<pre>
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<tt>df -P /usr
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</tt>
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</pre>
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</li>
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<li>
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<p>Assuming that <b>/usr/src</b> is part of the <b>/usr</b> file system, the following produces the same output as the previous
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example:</p>
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<pre>
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<tt>df -P /usr/src
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</tt>
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</pre>
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</li>
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</ol>
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</blockquote>
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<h4><a name="tag_04_36_18"></a>RATIONALE</h4>
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<blockquote>
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<p>The behavior of <i>df</i> with the <b>-P</b> option is the default action of the 4.2 BSD <i>df</i> utility. The uppercase
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<b>-P</b> was selected to avoid collision with a known industry extension using <b>-p</b>.</p>
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<p>Historical <i>df</i> implementations vary considerably in their default output. It was therefore necessary to describe the
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default output in a loose manner to accommodate all known historical implementations and to add a portable option ( <b>-P</b>) to
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provide information in a portable format.</p>
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<p>The use of 512-byte units is historical practice and maintains compatibility with <a href="../utilities/ls.html"><i>ls</i></a>
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and other utilities in this volume of IEEE Std 1003.1-2001. This does not mandate that the file system itself be based on
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512-byte blocks. The <b>-k</b> option was added as a compromise measure. It was agreed by the standard developers that 512 bytes
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was the best default unit because of its complete historical consistency on System V (<i>versus</i> the mixed 512/1024-byte usage
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on BSD systems), and that a <b>-k</b> option to switch to 1024-byte units was a good compromise. Users who prefer the more logical
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1024-byte quantity can easily alias <i>df</i> to <i>df</i> <b>-k</b> without breaking many historical scripts relying on the
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512-byte units.</p>
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<p>It was suggested that <i>df</i> and the various related utilities be modified to access a <i>BLOCKSIZE</i> environment variable
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to achieve consistency and user acceptance. Since this is not historical practice on any system, it is left as a possible area for
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system extensions and will be re-evaluated in a future version if it is widely implemented.</p>
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</blockquote>
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<h4><a name="tag_04_36_19"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_36_20"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="find.html"><i>find</i></a></p>
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</blockquote>
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<h4><a name="tag_04_36_21"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 2.</p>
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</blockquote>
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<h4><a name="tag_04_36_22"></a>Issue 6</h4>
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<blockquote>
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<p>This utility is marked as part of the User Portability Utilities option.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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