1DU(P) POSIX Programmer's Manual DU(P)
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6 du - estimate file space usage
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9 du [-a | -s][-kx][-H | -L][file ...]
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12 By default, the du utility shall write to standard output the size of
13 the file space allocated to, and the size of the file space allocated
14 to each subdirectory of, the file hierarchy rooted in each of the spec‐
15 ified files. By default, when a symbolic link is encountered on the
16 command line or in the file hierarchy, du shall count the size of the
17 symbolic link (rather than the file referenced by the link), and shall
18 not follow the link to another portion of the file hierarchy. The size
19 of the file space allocated to a file of type directory shall be
20 defined as the sum total of space allocated to all files in the file
21 hierarchy rooted in the directory plus the space allocated to the
22 directory itself.
23 When du cannot stat() files or stat() or read directories, it shall
25 report an error condition and the final exit status is affected. Files
26 with multiple links shall be counted and written for only one entry.
27 The directory entry that is selected in the report is unspecified. By
28 default, file sizes shall be written in 512-byte units, rounded up to
29 the next 512-byte unit.
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32 The du utility shall conform to the Base Definitions volume of
33 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
34 The following options shall be supported:
36 -a In addition to the default output, report the size of each file
38 not of type directory in the file hierarchy rooted in the speci‐
39 fied file. Regardless of the presence of the -a option, non-
40 directories given as file operands shall always be listed.
41 -H If a symbolic link is specified on the command line, du shall
43 count the size of the file or file hierarchy referenced by the
44 link.
45 -k Write the files sizes in units of 1024 bytes, rather than the
47 default 512-byte units.
48 -L If a symbolic link is specified on the command line or encoun‐
50 tered during the traversal of a file hierarchy, du shall count
51 the size of the file or file hierarchy referenced by the link.
52 -s Instead of the default output, report only the total sum for
54 each of the specified files.
55 -x When evaluating file sizes, evaluate only those files that have
57 the same device as the file specified by the file operand.
58 Specifying more than one of the mutually-exclusive options -H and -L
61 shall not be considered an error. The last option specified shall
62 determine the behavior of the utility.
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65 The following operand shall be supported:
66 file The pathname of a file whose size is to be written. If no file
68 is specified, the current directory shall be used.
69
72 Not used.
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75 None.
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78 The following environment variables shall affect the execution of du:
79 LANG Provide a default value for the internationalization variables
81 that are unset or null. (See the Base Definitions volume of
82 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
83 ables for the precedence of internationalization variables used
84 to determine the values of locale categories.)
85 LC_ALL If set to a non-empty string value, override the values of all
87 the other internationalization variables.
88 LC_CTYPE
90 Determine the locale for the interpretation of sequences of
91 bytes of text data as characters (for example, single-byte as
92 opposed to multi-byte characters in arguments).
93 LC_MESSAGES
95 Determine the locale that should be used to affect the format
96 and contents of diagnostic messages written to standard error.
97 NLSPATH
99 Determine the location of message catalogs for the processing of
100 LC_MESSAGES .
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104 Default.
105
107 The output from du shall consist of the amount of space allocated to a
108 file and the name of the file, in the following format:
109 "%d %s\n", <size>, <pathname>
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114 The standard error shall be used only for diagnostic messages.
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117 None.
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120 None.
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123 The following exit values shall be returned:
124 0 Successful completion.
126 >0 An error occurred.
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131 Default.
132 The following sections are informative.
134
136 None.
137
139 None.
140
142 The use of 512-byte units is historical practice and maintains compati‐
143 bility with ls and other utilities in this volume of
144 IEEE Std 1003.1-2001. This does not mandate that the file system itself
145 be based on 512-byte blocks. The -k option was added as a compromise
146 measure. It was agreed by the standard developers that 512 bytes was
147 the best default unit because of its complete historical consistency on
148 System V (versus the mixed 512/1024-byte usage on BSD systems), and
149 that a -k option to switch to 1024-byte units was a good compromise.
150 Users who prefer the 1024-byte quantity can easily alias du to du -k
151 without breaking the many historical scripts relying on the 512-byte
152 units.
153 The -b option was added to an early proposal to provide a resolution to
155 the situation where System V and BSD systems give figures for file
156 sizes in blocks, which is an implementation-defined concept. (In common
157 usage, the block size is 512 bytes for System V and 1024 bytes for BSD
158 systems.) However, -b was later deleted, since the default was eventu‐
159 ally decided as 512-byte units.
160 Historical file systems provided no way to obtain exact figures for the
162 space allocation given to files. There are two known areas of inaccura‐
163 cies in historical file systems: cases of indirect blocks being used by
164 the file system or sparse files yielding incorrectly high values. An
165 indirect block is space used by the file system in the storage of the
166 file, but that need not be counted in the space allocated to the file.
167 A sparse file is one in which an lseek() call has been made to a posi‐
168 tion beyond the end of the file and data has subsequently been written
169 at that point. A file system need not allocate all the intervening
170 zero-filled blocks to such a file. It is up to the implementation to
171 define exactly how accurate its methods are.
172 The -a and -s options were mutually-exclusive in the original version
174 of du. The POSIX Shell and Utilities description is implied by the lan‐
175 guage in the SVID where -s is described as causing "only the grand
176 total" to be reported. Some systems may produce output for -sa, but a
177 Strictly Conforming POSIX Shell and Utilities Application cannot use
178 that combination.
179 The -a and -s options were adopted from the SVID except that the System
181 V behavior of not listing non-directories explicitly given as operands,
182 unless the -a option is specified, was considered a bug; the BSD-based
183 behavior (report for all operands) is mandated. The default behavior of
184 du in the SVID with regard to reporting the failure to read files (it
185 produces no messages) was considered counter-intuitive, and thus it was
186 specified that the POSIX Shell and Utilities default behavior shall be
187 to produce such messages. These messages can be turned off with shell
188 redirection to achieve the System V behavior.
189 The -x option is historical practice on recent BSD systems. It has
191 been adopted by this volume of IEEE Std 1003.1-2001 because there was
192 no other historical method of limiting the du search to a single file
193 hierarchy. This limitation of the search is necessary to make it possi‐
194 ble to obtain file space usage information about a file system on which
195 other file systems are mounted, without having to resort to a lengthy
196 find and awk script.
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199 None.
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202 ls , the System Interfaces volume of IEEE Std 1003.1-2001, stat()
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205 Portions of this text are reprinted and reproduced in electronic form
206 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
207 -- Portable Operating System Interface (POSIX), The Open Group Base
208 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
209 Electrical and Electronics Engineers, Inc and The Open Group. In the
210 event of any discrepancy between this version and the original IEEE and
211 The Open Group Standard, the original IEEE and The Open Group Standard
212 is the referee document. The original Standard can be obtained online
213 at http://www.opengroup.org/unix/online.html .
214IEEE/The Open Group 2003 DU(P)