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DF(1P)			   POSIX Programmer's Manual			DF(1P)

       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 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, if no options other
       than −t are specified, the number of free file slots, or inodes, avail‐
       able;  when  −t	is specified, the output shall contain the total allo‐
       cated 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 figures.

       −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 contain‐
		 ing 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	 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).

		 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


       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

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

	   "%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

       <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 cur‐
		 rently 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	 high‐
		 est 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

       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 follow‐
	   ing 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  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 format.

       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
       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 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				DF(1P)

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