1DU(1P) POSIX Programmer's Manual DU(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 du - estimate file space usage
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15 du [-a | -s][-kx][-H | -L][file ...]
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18 By default, the du utility shall write to standard output the size of
19 the file space allocated to, and the size of the file space allocated
20 to each subdirectory of, the file hierarchy rooted in each of the spec‐
21 ified files. By default, when a symbolic link is encountered on the
22 command line or in the file hierarchy, du shall count the size of the
23 symbolic link (rather than the file referenced by the link), and shall
24 not follow the link to another portion of the file hierarchy. The size
25 of the file space allocated to a file of type directory shall be
26 defined as the sum total of space allocated to all files in the file
27 hierarchy rooted in the directory plus the space allocated to the
28 directory itself.
29 When du cannot stat() files or stat() or read directories, it shall
31 report an error condition and the final exit status is affected. Files
32 with multiple links shall be counted and written for only one entry.
33 The directory entry that is selected in the report is unspecified. By
34 default, file sizes shall be written in 512-byte units, rounded up to
35 the next 512-byte unit.
36
38 The du utility shall conform to the Base Definitions volume of
39 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
40 The following options shall be supported:
42 -a In addition to the default output, report the size of each file
44 not of type directory in the file hierarchy rooted in the speci‐
45 fied file. Regardless of the presence of the -a option, non-
46 directories given as file operands shall always be listed.
47 -H If a symbolic link is specified on the command line, du shall
49 count the size of the file or file hierarchy referenced by the
50 link.
51 -k Write the files sizes in units of 1024 bytes, rather than the
53 default 512-byte units.
54 -L If a symbolic link is specified on the command line or encoun‐
56 tered during the traversal of a file hierarchy, du shall count
57 the size of the file or file hierarchy referenced by the link.
58 -s Instead of the default output, report only the total sum for
60 each of the specified files.
61 -x When evaluating file sizes, evaluate only those files that have
63 the same device as the file specified by the file operand.
64 Specifying more than one of the mutually-exclusive options -H and -L
67 shall not be considered an error. The last option specified shall
68 determine the behavior of the utility.
69
71 The following operand shall be supported:
72 file The pathname of a file whose size is to be written. If no file
74 is specified, the current directory shall be used.
75
78 Not used.
79
81 None.
82
84 The following environment variables shall affect the execution of du:
85 LANG Provide a default value for the internationalization variables
87 that are unset or null. (See the Base Definitions volume of
88 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
89 ables for the precedence of internationalization variables used
90 to determine the values of locale categories.)
91 LC_ALL If set to a non-empty string value, override the values of all
93 the other internationalization variables.
94 LC_CTYPE
96 Determine the locale for the interpretation of sequences of
97 bytes of text data as characters (for example, single-byte as
98 opposed to multi-byte characters in arguments).
99 LC_MESSAGES
101 Determine the locale that should be used to affect the format
102 and contents of diagnostic messages written to standard error.
103 NLSPATH
105 Determine the location of message catalogs for the processing of
106 LC_MESSAGES .
107
110 Default.
111
113 The output from du shall consist of the amount of space allocated to a
114 file and the name of the file, in the following format:
115 "%d %s\n", <size>, <pathname>
118
120 The standard error shall be used only for diagnostic messages.
121
123 None.
124
126 None.
127
129 The following exit values shall be returned:
130 0 Successful completion.
132 >0 An error occurred.
134
137 Default.
138 The following sections are informative.
140
142 None.
143
145 None.
146
148 The use of 512-byte units is historical practice and maintains compati‐
149 bility with ls and other utilities in this volume of
150 IEEE Std 1003.1-2001. This does not mandate that the file system itself
151 be based on 512-byte blocks. The -k option was added as a compromise
152 measure. It was agreed by the standard developers that 512 bytes was
153 the best default unit because of its complete historical consistency on
154 System V (versus the mixed 512/1024-byte usage on BSD systems), and
155 that a -k option to switch to 1024-byte units was a good compromise.
156 Users who prefer the 1024-byte quantity can easily alias du to du -k
157 without breaking the many historical scripts relying on the 512-byte
158 units.
159 The -b option was added to an early proposal to provide a resolution to
161 the situation where System V and BSD systems give figures for file
162 sizes in blocks, which is an implementation-defined concept. (In common
163 usage, the block size is 512 bytes for System V and 1024 bytes for BSD
164 systems.) However, -b was later deleted, since the default was eventu‐
165 ally decided as 512-byte units.
166 Historical file systems provided no way to obtain exact figures for the
168 space allocation given to files. There are two known areas of inaccura‐
169 cies in historical file systems: cases of indirect blocks being used by
170 the file system or sparse files yielding incorrectly high values. An
171 indirect block is space used by the file system in the storage of the
172 file, but that need not be counted in the space allocated to the file.
173 A sparse file is one in which an lseek() call has been made to a posi‐
174 tion beyond the end of the file and data has subsequently been written
175 at that point. A file system need not allocate all the intervening
176 zero-filled blocks to such a file. It is up to the implementation to
177 define exactly how accurate its methods are.
178 The -a and -s options were mutually-exclusive in the original version
180 of du. The POSIX Shell and Utilities description is implied by the lan‐
181 guage in the SVID where -s is described as causing "only the grand
182 total" to be reported. Some systems may produce output for -sa, but a
183 Strictly Conforming POSIX Shell and Utilities Application cannot use
184 that combination.
185 The -a and -s options were adopted from the SVID except that the System
187 V behavior of not listing non-directories explicitly given as operands,
188 unless the -a option is specified, was considered a bug; the BSD-based
189 behavior (report for all operands) is mandated. The default behavior of
190 du in the SVID with regard to reporting the failure to read files (it
191 produces no messages) was considered counter-intuitive, and thus it was
192 specified that the POSIX Shell and Utilities default behavior shall be
193 to produce such messages. These messages can be turned off with shell
194 redirection to achieve the System V behavior.
195 The -x option is historical practice on recent BSD systems. It has
197 been adopted by this volume of IEEE Std 1003.1-2001 because there was
198 no other historical method of limiting the du search to a single file
199 hierarchy. This limitation of the search is necessary to make it possi‐
200 ble to obtain file space usage information about a file system on which
201 other file systems are mounted, without having to resort to a lengthy
202 find and awk script.
203
205 None.
206
208 ls, the System Interfaces volume of IEEE Std 1003.1-2001, stat()
209
211 Portions of this text are reprinted and reproduced in electronic form
212 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
213 -- Portable Operating System Interface (POSIX), The Open Group Base
214 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
215 Electrical and Electronics Engineers, Inc and The Open Group. In the
216 event of any discrepancy between this version and the original IEEE and
217 The Open Group Standard, the original IEEE and The Open Group Standard
218 is the referee document. The original Standard can be obtained online
219 at http://www.opengroup.org/unix/online.html .
220IEEE/The Open Group 2003 DU(1P)