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.TH DF "1P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

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.

.SH NAME

df

\(em report free disk space

.SH SYNOPSIS

.LP

.nf

df \fB[\fR\(mik\fB] [\fR\(miP|\(mit\fB] [\fIfile\fR...\fB]\fR

.fi

.SH DESCRIPTION

The

.IR 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

.IR file

operands; when none are specified, information shall be written for all

file systems. The format of the default output from

.IR df

is unspecified, but all space figures are reported in 512-byte units,

unless the

.BR \(mik

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

.BR \(mit

are specified, the number of free file slots, or

.IR inode s,

available; when

.BR \(mit

is specified, the output shall contain the total allocated space as well.

.SH OPTIONS

The

.IR df

utility shall conform to the Base Definitions volume of POSIX.1\(hy2008,

.IR "Section 12.2" ", " "Utility Syntax Guidelines".

.P

The following options shall be supported:

.IP "\fB\(mik\fP" 10

Use 1\|024-byte units, instead of the default 512-byte units, when

writing space figures.

.IP "\fB\(miP\fP" 10

Produce output in the format described in the STDOUT section.

.IP "\fB\(mit\fP" 10

Include total allocated-space figures in the output.

.SH OPERANDS

The following operand shall be supported:

.IP "\fIfile\fR" 10

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,

.BR /dev/dsk/0s1 )

is specified, the results are unspecified. If the

.IR file

operand names a file other than a special file containing a file

system,

.IR df

shall write the amount of free space in the file system containing the

specified

.IR file

operand.

Otherwise,

.IR df

shall write the amount of free space in that file system.

.SH STDIN

Not used.

.SH "INPUT FILES"

None.

.SH "ENVIRONMENT VARIABLES"

The following environment variables shall affect the execution of

.IR df :

.IP "\fILANG\fP" 10

Provide a default value for the internationalization variables that are

unset or null. (See the Base Definitions volume of POSIX.1\(hy2008,

.IR "Section 8.2" ", " "Internationalization Variables"

for the precedence of internationalization variables used to determine

the values of locale categories.)

.IP "\fILC_ALL\fP" 10

If set to a non-empty string value, override the values of all the

other internationalization variables.

.IP "\fILC_CTYPE\fP" 10

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).

.IP "\fILC_MESSAGES\fP" 10

.br

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.

.IP "\fINLSPATH\fP" 10

Determine the location of message catalogs for the processing of

.IR LC_MESSAGES .

.SH "ASYNCHRONOUS EVENTS"

Default.

.SH STDOUT

When both the

.BR \(mik

and

.BR \(miP

options are specified, the following header line shall be written (in

the POSIX locale):

.sp

.RS 4

.nf

\fB

"Filesystem 1024-blocks Used Available Capacity Mounted on\en"

.fi \fR

.P

.RE

.P

When the

.BR \(miP

option is specified without the

.BR \(mik

option, the following header line shall be written (in the POSIX

locale):

.sp

.RS 4

.nf

\fB

"Filesystem 512-blocks Used Available Capacity Mounted on\en"

.fi \fR

.P

.RE

.P

The implementation may adjust the spacing of the header line and the

individual data lines so that the information is presented in orderly

columns.

.P

The remaining output with

.BR \(miP

shall consist of one line of information for each specified

file system. These lines shall be formatted as follows:

.sp

.RS 4

.nf

\fB

"%s %d %d %d %d%% %s\en", <\fIfile system name\fR>, <\fItotal space\fR>,

    <\fIspace used\fR>, <\fIspace free\fR>, <\fIpercentage used\fR>,

    <\fIfile system root\fR>

.fi \fR

.P

.RE

.P

In the following list, all quantities expressed in 512-byte units

(1\|024-byte when

.BR \(mik

is specified) shall be rounded up to the next higher unit. The fields

are:

.IP "<\fIfile\ system\ name\fP>" 10

.br

The name of the file system, in an implementation-defined format.

.IP "<\fItotal\ space\fP>" 10

The total size of the file system in 512-byte units. The exact meaning

of this figure is implementation-defined, but should include

<\fIspace\ used\fP>, <\fIspace\ free\fP>, plus any space reserved by

the system not normally available to a user.

.IP "<\fIspace\ used\fP>" 10

The total amount of space allocated to existing files in the

file system, in 512-byte units.

.IP "<\fIspace\ free\fP>" 10

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.

.IP "<\fIpercentage\ used\fP>" 10

.br

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:

.RS 10 

.sp

.RS 4

.nf

\fB

<\fIspace used\fR>/( <\fIspace used\fR>+ <\fIspace free\fR>)

.fi \fR

.P

.RE

.P

expressed as a percentage. This percentage may be greater than 100 if

<\fIspace\ free\fP> 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.

.RE

.IP "<\fIfile\ system\ root\fP>" 10

.br

The directory below which the file system hierarchy appears.

.P

The output format is unspecified when

.BR \(mit

is used.

.SH STDERR

The standard error shall be used only for diagnostic messages.

.SH "OUTPUT FILES"

None.

.SH "EXTENDED DESCRIPTION"

None.

.SH "EXIT STATUS"

The following exit values shall be returned:

.IP "\00" 6

Successful completion.

.IP >0 6

An error occurred.

.SH "CONSEQUENCES OF ERRORS"

Default.

.LP

.IR "The following sections are informative."

.SH "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.

.P

On large file systems, the calculation specified for percentage used

can create huge rounding errors.

.SH EXAMPLES

.IP " 1." 4

The following example writes portable information about the

.BR /usr

file system:

.RS 4 

.sp

.RS 4

.nf

\fB

df \(miP /usr

.fi \fR

.P

.RE

.RE

.IP " 2." 4

Assuming that

.BR /usr/src

is part of the

.BR /usr

file system, the following produces the same output as the previous

example:

.RS 4 

.sp

.RS 4

.nf

\fB

df \(miP /usr/src

.fi \fR

.P

.RE

.RE

.SH RATIONALE

The behavior of

.IR df

with the

.BR \(miP

option is the default action of the 4.2 BSD

.IR df

utility. The uppercase

.BR \(miP

was selected to avoid collision with a known industry extension using

.BR \(mip .

.P

Historical

.IR 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 (\c

.BR \(miP )

to provide information in a portable format.

.P

The use of 512-byte units is historical practice and maintains

compatibility with

.IR ls

and other utilities in this volume of POSIX.1\(hy2008. This does not mandate that the

file system itself be based on 512-byte blocks. The

.BR \(mik

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 (\fIversus\fP the mixed

512/1\|024-byte usage on BSD systems), and that a

.BR \(mik

option to switch to 1\|024-byte units was a good compromise. Users who

prefer the more logical 1\|024-byte quantity can easily alias

.IR df

to

.IR df

.BR \(mik

without breaking many historical scripts relying on the 512-byte

units.

.P

It was suggested that

.IR df

and the various related utilities be modified to access a

.IR 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.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "\fIfind\fR\^"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "Chapter 8" ", " "Environment Variables",

.IR "Section 12.2" ", " "Utility Syntax Guidelines"

.SH COPYRIGHT

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 .