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

NAME
       df - report free disk space

SYNOPSIS
       df [-k][-P|-t][file...]

DESCRIPTION
       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 fig‐
       ures 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.

OPTIONS
       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 figures.

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

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

OPERANDS
       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 direc‐
	      tory,  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.

STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       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	 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
	      and informative messages written to standard output.

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

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       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 fol‐
       lows:

	      "%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  for‐
	      mat.

       <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 with‐
	      out  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 calcu‐
	      lated 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.

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
       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.

EXAMPLES
	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 follow‐
	   ing produces the same output as the previous example:

	   df -P /usr/src

RATIONALE
       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  out‐
       put.  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 for‐
       mat.

       The use of 512-byte units is historical practice and maintains compati‐
       bility	 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.

FUTURE DIRECTIONS
       None.

SEE ALSO
       find

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,  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				 DF(P)
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