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 (con-
       sult 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 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
       The  du utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guide-
       lines.

       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  refer-
              enced 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  IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the precedence of international-
              ization 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 stan-
              dard 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 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  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 explic-
       itly 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 pro-
       duces 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 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
       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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                        DU(1P)