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

PROLOG         top

       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.

NAME         top

       du — estimate file space usage

SYNOPSIS         top

       du [−a|−s] [−kx] [−H|−L] [file...]

DESCRIPTION         top

       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.

OPTIONS         top

       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

       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         top

       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         top

       Not used.

INPUT FILES         top



       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

       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).

                 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.



STDOUT         top

       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         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top




EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.



       The following sections are informative.



EXAMPLES         top


RATIONALE         top

       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

       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.



SEE ALSO         top


       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)

COPYRIGHT         top

       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 .

       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 .

IEEE/The Open Group                 2013                              DU(1P)