df(1p) — Linux manual page


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.1‐2017, 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

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base
                 Definitions volume of POSIX.1‐2017, 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).

                 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.



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 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 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 mounted.

       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.1‐2017. 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

       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.1‐2017, 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 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                            DF(1P)