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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.
Files with multiple links shall be counted and written for only one
entry. 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.1‐2008, 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. Regardless of the presence of the −a
option, non-directories given as file operands shall always
be 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.1‐2008, 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.1‐2008. 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.1‐2008 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.
None.
ls(1p)
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1‐2008, fstatat(3p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/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 2013 DU(1P)
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