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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 dif-
       fer (consult the corresponding 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 invok-
       ing user has appropriate read access. File systems shall be specified by the file operands; when none are spec-
       ified,  information shall be written for all file systems. The format of the default output from df is unspeci-
       fied, 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 allo-
       cated space as well.

OPTIONS
       The df utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syn-
       tax 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 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 Variables for  the  prece-
              dence 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  exam-
              ple, 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 writ-
              ten 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 informa-
       tion 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  nor-
              mally 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 appropri-
              ate 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 sys-
              tem. 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 per-
       centage 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  pre-
           vious 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 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 histor-
       ical scripts relying on the 512-byte units.

       It was suggested that df and the various related utilities be modified to access a BLOCKSIZE environment  vari-
       able  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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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)