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  sys-
       tems.  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.

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(P)