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

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 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 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  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
", <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 compro-
       mise measure.  It was agreed by the standard developers that 512 bytes was the best default unit because of its complete historical consis-
       tency  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 com-
       promise. 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 inac-
       curacies in historical file systems: cases of indirect blocks being used by the file system or sparse files yielding incorrectly high  val-
       ues.  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 imple-
       mentation 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 oper-
       ands,  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 pos-
       sible 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 Technol-
       ogy -- 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(P)