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       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.


       df — report free disk space


       df [−k] [−P|−t] [file...]


       The  df  utility shall write the amount of available space and file slots for file systems
       on which the invoking user has appropriate read access. File systems shall be specified by
       the  file  operands;  when  none  are specified, information shall be written for all file
       systems. The format of the default output from df is unspecified, but  all  space  figures
       are  reported  in  512-byte  units,  unless  the −k option is specified. This output shall
       contain at least the file system names, amount of available space on each  of  these  file
       systems, and, if no options other than −t are specified, the number of free file slots, or
       inodes, available; when −t is specified, the output  shall  contain  the  total  allocated
       space as well.


       The df utility shall conform to the Base Definitions volume of POSIX.1‐2008, Section 12.2,
       Utility Syntax Guidelines.

       The following options shall be supported:

       −k        Use 1024-byte units, instead of the default 512-byte units, when  writing  space

       −P        Produce output in the format described in the STDOUT section.

       −t        Include total allocated-space figures in the output.


       The following operand shall be supported:

       file      A pathname of a file within the hierarchy of the desired file system.  If a file
                 other than a FIFO, a regular file, a directory, or a special  file  representing
                 the  device containing the file system (for example, /dev/dsk/0s1) is specified,
                 the results are unspecified. If the file operand  names  a  file  other  than  a
                 special  file  containing a file system, df shall write the amount of free space
                 in the file system containing the specified file operand.  Otherwise,  df  shall
                 write the amount of free space in that file system.


       Not used.




       The following environment variables shall affect the execution of df:

       LANG      Provide a default value for the internationalization variables that are unset or
                 null.  (See  the  Base  Definitions  volume  of   POSIX.1‐2008,   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

                 Determine  the  locale  that should be used to affect the format and contents of
                 diagnostic messages written to standard error and informative  messages  written
                 to standard output.

       NLSPATH   Determine the location of message catalogs for the processing of LC_MESSAGES.




       When  both the −k and −P options are specified, the following header line shall be written
       (in the POSIX locale):

           "Filesystem 1024-blocks Used Available Capacity Mounted on\n"

       When the −P option is specified without the −k option, the following header line shall  be
       written (in the POSIX locale):

           "Filesystem 512-blocks Used Available Capacity Mounted on\n"

       The implementation may adjust the spacing of the header line and the individual data lines
       so that the information is presented in orderly columns.

       The remaining output with −P shall consist of one line of information for  each  specified
       file system. These lines shall be formatted as follows:

           "%s %d %d %d %d%% %s\n", <file system name>, <total space>,
               <space used>, <space free>, <percentage used>,
               <file system root>

       In  the  following  list, all quantities expressed in 512-byte units (1024-byte when −k is
       specified) shall be rounded up to the next higher unit. The fields are:

       <file system name>
                 The name of the file system, in an implementation-defined format.

       <total space>
                 The total size of the file system in 512-byte units. The exact meaning  of  this
                 figure is implementation-defined, but should include <space used>, <space free>,
                 plus any space reserved by the system not normally available to a user.

       <space used>
                 The total amount of space allocated to existing files in  the  file  system,  in
                 512-byte units.

       <space free>
                 The  total  amount of space available within the file system for the creation of
                 new files by unprivileged users, in 512-byte units. When  this  figure  is  less
                 than  or  equal to zero, it shall not be possible to create any new files on the
                 file system without first deleting others, unless the  process  has  appropriate
                 privileges. The figure written may be less than zero.

       <percentage used>
                 The  percentage  of  the normally available space that is currently allocated to
                 all files on the file system. This shall be calculated using the fraction:

                     <space used>/( <space used>+ <space free>)

                 expressed  as  a  percentage.  This  percentage  may  be  greater  than  100  if
                 <space free>  is  less  than  zero. The percentage value shall be expressed as a
                 positive integer, with any fractional result causing it to  be  rounded  to  the
                 next highest integer.

       <file system root>
                 The directory below which the file system hierarchy appears.

       The output format is unspecified when −t is used.


       The standard error shall be used only for diagnostic messages.






       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.



       The following sections are informative.


       On  most  systems, the ``name of the file system, in an implementation-defined format'' is
       the special file on which the file system is mounted.

       On large file systems, the calculation specified  for  percentage  used  can  create  huge
       rounding errors.


        1. The following example writes portable information about the /usr file system:

               df −P /usr

        2. Assuming  that  /usr/src  is  part of the /usr file system, the following produces the
           same output as the previous example:

               df −P /usr/src


       The behavior of df with the −P option is the default action of the 4.2 BSD df utility. The
       uppercase −P was selected to avoid collision with a known industry extension using −p.

       Historical  df implementations vary considerably in their default output. It was therefore
       necessary to describe the default output in  a  loose  manner  to  accommodate  all  known
       historical  implementations  and to add a portable option (−P) to provide information in a
       portable format.

       The use of 512-byte units is historical practice and maintains compatibility 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 more logical 1024-byte quantity can easily alias df to df −k  without
       breaking many historical scripts relying on the 512-byte units.

       It  was  suggested  that  df  and  the  various  related utilities be modified to access a
       BLOCKSIZE environment variable to achieve consistency and user acceptance. Since  this  is
       not historical practice on any system, it is left as a possible area for system extensions
       and will be re-evaluated in a future version if it is widely implemented.





       The Base Definitions volume of POSIX.1‐2008, Chapter  8,  Environment  Variables,  Section
       12.2, Utility Syntax Guidelines


       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 Electrical 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 .

       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 .