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

PROLOG
       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
       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 spec-
       ified  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
       The  du  utility  shall  conform  to  the  Base  Definitions  volume of
       IEEE Std 1003.1-2001, 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 speci-
              fied 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  encoun-
              tered  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
              IEEE Std 1003.1-2001,  Section  8.2,  Internationalization Vari-
              ables 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 compati-
       bility   with   ls   and   other   utilities   in   this   volume    of
       IEEE Std 1003.1-2001. 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 eventu-
       ally 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 inaccura-
       cies 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  posi-
       tion  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 lan-
       guage 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 IEEE Std 1003.1-2001 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 possi-
       ble 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
       None.
SEE ALSO
       ls, the System Interfaces volume of IEEE Std 1003.1-2001, stat()
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  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 .

IEEE/The Open Group                  2003                               DU(1P)