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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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DU(1P) POSIX Programmer's Manual DU(1P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
du — estimate file space usage
du [-a|-s] [-kx] [-H|-L] [file...]
By default, the du utility shall write to standard output the size
of the file space allocated to, and the size of the file space
allocated to each subdirectory of, the file hierarchy rooted in
each of the specified files. By default, when a symbolic link is
encountered on the command line or in the file hierarchy, du shall
count the size of the symbolic link (rather than the file
referenced by the link), and shall not follow the link to another
portion of the file hierarchy. The size of the file space
allocated to a file of type directory shall be defined as the sum
total of space allocated to all files in the file hierarchy rooted
in the directory plus the space allocated to the directory itself.
When du cannot stat() files or stat() or read directories, it
shall report an error condition and the final exit status is
affected. A file that occurs multiple times under one file operand
and that has a link count greater than 1 shall be counted and
written for only one entry. It is implementation-defined whether a
file that has a link count no greater than 1 is counted and
written just once, or is counted and written for each occurrence.
It is implementation-defined whether a file that occurs under one
file operand is counted for other file operands. The directory
entry that is selected in the report is unspecified. By default,
file sizes shall be written in 512-byte units, rounded up to the
next 512-byte unit.
The du utility shall conform to the Base Definitions volume of
POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
-a In addition to the default output, report the size of
each file not of type directory in the file hierarchy
rooted in the specified file. The -a option shall not
affect whether non-directories given as file operands
are listed.
-H If a symbolic link is specified on the command line, du
shall count the size of the file or file hierarchy
referenced by the link.
-k Write the files sizes in units of 1024 bytes, rather
than the default 512-byte units.
-L If a symbolic link is specified on the command line or
encountered during the traversal of a file hierarchy, du
shall count the size of the file or file hierarchy
referenced by the link.
-s Instead of the default output, report only the total sum
for each of the specified files.
-x When evaluating file sizes, evaluate only those files
that have the same device as the file specified by the
file operand.
Specifying more than one of the mutually-exclusive options -H and
-L shall not be considered an error. The last option specified
shall determine the behavior of the utility.
The following operand shall be supported:
file The pathname of a file whose size is to be written. If
no file is specified, the current directory shall be
used.
Not used.
None.
The following environment variables shall affect the execution of
du:
LANG Provide a default value for the internationalization
variables that are unset or null. (See the Base
Definitions volume of POSIX.1‐2017, Section 8.2,
Internationalization Variables for the precedence of
internationalization variables used to determine the
values of locale categories.)
LC_ALL If set to a non-empty string value, override the values
of all the other internationalization variables.
LC_CTYPE Determine the locale for the interpretation of sequences
of bytes of text data as characters (for example,
single-byte as opposed to multi-byte characters in
arguments).
LC_MESSAGES
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to
standard error.
NLSPATH Determine the location of message catalogs for the
processing of LC_MESSAGES.
Default.
The output from du shall consist of the amount of space allocated
to a file and the name of the file, in the following format:
"%d %s\n", <size>, <pathname>
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
None.
None.
The use of 512-byte units is historical practice and maintains
compatibility with ls and other utilities in this volume of
POSIX.1‐2017. This does not mandate that the file system itself be
based on 512-byte blocks. The -k option was added as a compromise
measure. It was agreed by the standard developers that 512 bytes
was the best default unit because of its complete historical
consistency on System V (versus the mixed 512/1024-byte usage on
BSD systems), and that a -k option to switch to 1024-byte units
was a good compromise. Users who prefer the 1024-byte quantity can
easily alias du to du -k without breaking the many historical
scripts relying on the 512-byte units.
The -b option was added to an early proposal to provide a
resolution to the situation where System V and BSD systems give
figures for file sizes in blocks, which is an implementation-
defined concept. (In common usage, the block size is 512 bytes for
System V and 1024 bytes for BSD systems.) However, -b was later
deleted, since the default was eventually decided as 512-byte
units.
Historical file systems provided no way to obtain exact figures
for the space allocation given to files. There are two known areas
of inaccuracies in historical file systems: cases of indirect
blocks being used by the file system or sparse files yielding
incorrectly high values. An indirect block is space used by the
file system in the storage of the file, but that need not be
counted in the space allocated to the file. A sparse file is one
in which an lseek() call has been made to a position beyond the
end of the file and data has subsequently been written at that
point. A file system need not allocate all the intervening zero-
filled blocks to such a file. It is up to the implementation to
define exactly how accurate its methods are.
The -a and -s options were mutually-exclusive in the original
version of du. The POSIX Shell and Utilities description is
implied by the language in the SVID where -s is described as
causing ``only the grand total'' to be reported. Some systems may
produce output for -sa, but a Strictly Conforming POSIX Shell and
Utilities Application cannot use that combination.
The -a and -s options were adopted from the SVID except that the
System V behavior of not listing non-directories explicitly given
as operands, unless the -a option is specified, was considered a
bug; the BSD-based behavior (report for all operands) is mandated.
The default behavior of du in the SVID with regard to reporting
the failure to read files (it produces no messages) was considered
counter-intuitive, and thus it was specified that the POSIX Shell
and Utilities default behavior shall be to produce such messages.
These messages can be turned off with shell redirection to achieve
the System V behavior.
The -x option is historical practice on recent BSD systems. It has
been adopted by this volume of POSIX.1‐2017 because there was no
other historical method of limiting the du search to a single file
hierarchy. This limitation of the search is necessary to make it
possible to obtain file space usage information about a file
system on which other file systems are mounted, without having to
resort to a lengthy find and awk script.
A future version of this standard may require that a file that
occurs multiple times shall be counted and written for only one
entry, even if the occurrences are under different file operands.
ls(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1‐2017, fstatat(3p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 DU(1P)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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