du(1p) — Linux manual page


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. 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         top

       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         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

STDIN         top

       Not used.

INPUT FILES         top



       The following environment variables shall affect the execution of

       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).

                 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.1‐2017. 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

       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.

SEE ALSO         top


       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)

COPYRIGHT         top

       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)