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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
DF(1P) POSIX Programmer's Manual DF(1P)
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.
df — report free disk space
df [−k] [−P|−t] [file...]
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.
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
section.
−t Include total allocated-space figures in the output.
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
system.
Not used.
None.
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
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.
Default.
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
appears.
The output format is unspecified when −t is used.
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
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.
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
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.
None.
find(1p)
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
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 http://www.unix.org/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 2013 DF(1P)