<s>
(	O
abbreviation	O
for	O
disk	O
free	O
)	O
is	O
a	O
standard	O
Unix	B-Application
command	I-Application
used	O
to	O
display	O
the	O
amount	O
of	O
available	O
disk	O
space	O
for	O
file	B-Application
systems	I-Application
on	O
which	O
the	O
invoking	O
user	O
has	O
appropriate	O
read	O
access	O
.	O
</s>
<s>
is	O
typically	O
implemented	O
using	O
the	O
statfs	O
or	O
statvfs	O
system	B-Operating_System
calls	I-Operating_System
.	O
</s>
<s>
for	O
Unix-like	B-Operating_System
systems	I-Operating_System
is	O
part	O
of	O
the	O
X/Open	O
Portability	O
Guide	O
since	O
issue	O
2	O
of	O
1987	O
.	O
</s>
<s>
It	O
was	O
inherited	O
into	O
the	O
first	O
version	O
of	O
POSIX	O
and	O
the	O
Single	O
Unix	B-Application
Specification	O
.	O
</s>
<s>
It	O
first	O
appeared	O
in	O
Version	B-Operating_System
1	I-Operating_System
AT&T	I-Operating_System
Unix	I-Operating_System
.	O
</s>
<s>
The	O
version	O
of	O
bundled	O
in	O
GNU	B-Application
coreutils	I-Application
was	O
written	O
by	O
Torbjorn	O
Granlund	O
,	O
David	O
MacKenzie	O
,	O
and	O
Paul	O
Eggert	O
.	O
</s>
<s>
The	O
command	B-Application
is	O
available	O
as	O
a	O
separate	O
package	O
for	O
Microsoft	B-Application
Windows	I-Application
as	O
part	O
of	O
the	O
UnxUtils	B-Application
collection	O
of	O
native	B-Language
Win32	B-Library
ports	O
of	O
common	O
GNU	B-Operating_System
Unix-like	B-Operating_System
utilities	O
.	O
</s>
<s>
The	O
Single	O
UNIX	B-Application
Specification	O
specifications	O
for	O
are	O
:	O
</s>
<s>
df	B-Device
 [ -k ] 	O
 [ -P|-t ] 	O
 [ -del ] 	O
file	O
...	O
</s>
<s>
Display	O
in	O
more	O
easily	O
human	B-General_Concept
readable	I-General_Concept
units	O
such	O
as	O
KB	O
,	O
MB	O
,	O
GB	O
or	O
TB	O
.	O
</s>
<s>
Most	O
implementations	O
of	O
in	O
Unix	B-Application
and	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
include	O
extra	O
options	O
.	O
</s>
<s>
The	O
BSD	B-Operating_System
and	O
GNU	B-Application
coreutils	I-Application
versions	O
include	O
,	O
which	O
lists	O
free	O
space	O
in	O
human	B-General_Concept
readable	I-General_Concept
format	I-General_Concept
displaying	O
units	O
with	O
the	O
appropriate	O
SI	O
prefix	O
(	O
e.g.	O
</s>
<s>
10	O
MB	O
)	O
,	O
,	O
which	O
lists	O
inode	B-Application
usage	O
,	O
and	O
,	O
restricting	O
display	O
to	O
only	O
local	O
filesystems	B-Application
.	O
</s>
<s>
GNU	B-Operating_System
includes	O
as	O
well	O
,	O
listing	O
filesystem	B-Application
type	O
information	O
,	O
but	O
the	O
GNU	B-Operating_System
shows	O
the	O
sizes	O
in	O
1K	O
blocks	O
by	O
default	O
.	O
</s>
<s>
The	O
Single	O
Unix	B-Application
Specification	O
(	O
SUS	O
)	O
specifies	O
by	O
original	O
space	O
is	O
reported	O
in	O
blocks	O
of	O
512	O
bytes	O
,	O
and	O
that	O
at	O
a	O
minimum	O
,	O
the	O
file	B-Application
system	I-Application
names	O
and	O
the	O
amount	O
of	O
free	O
space	O
.	O
</s>
<s>
This	O
does	O
not	O
mandate	O
that	O
the	O
file	B-Application
system	I-Application
itself	O
be	O
based	O
on	O
512-byte	O
blocks	O
.	O
</s>
<s>
It	O
was	O
agreed	O
by	O
the	O
standard	O
developers	O
that	O
512	O
bytes	O
was	O
the	O
best	O
default	O
unit	O
because	O
of	O
its	O
complete	O
historical	O
consistency	O
on	O
System	B-Operating_System
V	I-Operating_System
(	O
versus	O
the	O
mixed	O
512/1024	O
-byte	O
usage	O
on	O
BSD	B-Operating_System
systems	O
)	O
,	O
and	O
that	O
a	O
option	O
to	O
switch	O
to	O
1024-byte	O
units	O
was	O
a	O
good	O
compromise	O
.	O
</s>
<s>
The	O
output	O
with	O
consists	O
of	O
one	O
line	O
of	O
information	O
for	O
each	O
specified	O
file	B-Application
system	I-Application
.	O
</s>
<s>
The	O
name	O
of	O
the	O
file	B-Application
system	I-Application
,	O
in	O
an	O
implementation-defined	O
format	O
.	O
</s>
<s>
The	O
total	O
size	O
of	O
the	O
file	B-Application
system	I-Application
in	O
512-byte	O
units	O
.	O
</s>
<s>
The	O
total	O
amount	O
of	O
space	O
allocated	O
to	O
existing	O
files	O
in	O
the	O
file	B-Application
system	I-Application
,	O
in	O
512-byte	O
units	O
.	O
</s>
<s>
The	O
total	O
amount	O
of	O
space	O
available	O
within	O
the	O
file	B-Application
system	I-Application
for	O
the	O
creation	O
of	O
new	O
files	O
by	O
unprivileged	O
users	O
,	O
in	O
512-byte	O
units	O
.	O
</s>
<s>
When	O
this	O
figure	O
is	O
less	O
than	O
or	O
equal	O
to	O
zero	O
,	O
it	O
shall	O
not	O
be	O
possible	O
to	O
create	O
any	O
new	O
files	O
on	O
the	O
file	B-Application
system	I-Application
without	O
first	O
deleting	O
others	O
,	O
unless	O
the	O
process	O
has	O
appropriate	O
privileges	O
.	O
</s>
<s>
The	O
percentage	O
of	O
the	O
normally	O
available	O
space	O
that	O
is	O
currently	O
allocated	O
to	O
all	O
files	O
on	O
the	O
file	B-Application
system	I-Application
.	O
</s>
<s>
Example	O
outputs	O
of	O
the	O
df	B-Device
command	B-Application
:	O
</s>
