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

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

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 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 num-
       ber 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 directory,	or
	      a special file representing the device containing the file system (for example, /dev/dsk/0s1)  is specified, the results are unspec-
	      ified.  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  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 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
"

       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
"

       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
", <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.

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 following 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 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 compro-
       mise measure.  It was agreed by the standard developers that 512 bytes was the best default unit because of its complete historical consis-
       tency  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 com-
       promise. 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 Technol-
       ogy -- 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(1P)