DU(1)                      POSIX Programmer's Manual                     DU(1)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       du -- estimate file space usage

SYNOPSIS
       du [[-a|-s]] [[-kx]] [[-H|-L]] [[file...]]

DESCRIPTION
       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.

OPTIONS
       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.

OPERANDS
       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.

STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       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.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       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>

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       None.

EXAMPLES
       None.

RATIONALE
       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.

FUTURE DIRECTIONS
       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.

SEE ALSO
       ls

       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()

COPYRIGHT
       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(1)
