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       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  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  IEEE Std 1003.1-2001,
       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.  Otherwise, df shall write the amount of free space in the
              file system containing the specified file operand.


       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  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.

              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.

              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 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 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.






       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 .