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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 |
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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.1‐2017, 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
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.1‐2017, 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).
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.1‐2017. 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
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.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, 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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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