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

PROLOG         top

       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.

NAME         top

       df — report free disk space

SYNOPSIS         top

       df [−k] [−P|−t] [file...]

DESCRIPTION         top

       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, if no options other than −t are specified, the number
       of free file slots, or inodes, available; when −t is specified, the
       output shall contain the total allocated space as well.

OPTIONS         top

       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

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

OPERANDS         top

       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. 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

STDIN         top

       Not used.

INPUT FILES         top



       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 POSIX.1‐2008, Section 8.2, Internationalization
                 Variables for the precedence of internationalization
                 variables used to determine the values of locale

       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

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



STDOUT         top

       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

           "%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
                 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

       The output format is unspecified when −t is used.

STDERR         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top




EXIT STATUS         top

       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.

EXAMPLES         top

        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         top

       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
       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.



SEE ALSO         top


       The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT         top

       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 Electrical 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 .

       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 .

IEEE/The Open Group                 2013                              DF(1P)