DU(1P) - phpMan

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
       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  oper-
                 and.
       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  vari-
                 ables  that are unset or null. (See the Base Definitions vol-
                 ume of POSIX.1-2008, 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 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 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
       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 his-
       torical 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 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()
COPYRIGHT
       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 Electri-
       cal  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 http://www.unix.org/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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                               DU(1P)