<s>
In	O
classic	B-Application
Mac	I-Application
OS	I-Application
System	B-Operating_System
7	I-Operating_System
and	O
later	O
,	O
and	O
in	O
macOS	B-Operating_System
,	O
an	O
alias	B-Application
is	O
a	O
small	O
file	O
that	O
represents	O
another	O
object	O
in	O
a	O
local	O
,	O
remote	O
,	O
or	O
removable	O
file	B-Application
system	I-Application
and	O
provides	O
a	O
dynamic	O
link	O
to	O
it	O
;	O
the	O
target	O
object	O
may	O
be	O
moved	O
or	O
renamed	O
,	O
and	O
the	O
alias	B-Application
will	O
still	O
link	O
to	O
it	O
(	O
unless	O
the	O
original	O
file	O
is	O
recreated	O
;	O
such	O
an	O
alias	B-Application
is	O
ambiguous	O
and	O
how	O
it	O
is	O
resolved	O
depends	O
on	O
the	O
version	O
of	O
macOS	B-Operating_System
)	O
.	O
</s>
<s>
It	O
is	O
similar	O
to	O
the	O
Unix	B-Application
symbolic	B-Application
link	I-Application
,	O
but	O
with	O
the	O
distinction	O
of	O
working	O
even	O
if	O
the	O
target	O
file	O
moves	O
to	O
another	O
location	O
on	O
the	O
same	O
disk	O
(	O
in	O
this	O
case	O
it	O
acts	O
like	O
a	O
hard	B-Application
link	I-Application
,	O
but	O
the	O
source	O
and	O
target	O
of	O
the	O
link	O
may	O
be	O
on	O
different	O
filesystems	B-Application
,	O
and	O
the	O
target	O
of	O
the	O
link	O
may	O
be	O
a	O
directory	O
)	O
.	O
</s>
<s>
As	O
a	O
descendant	O
of	O
BSD	B-Operating_System
,	O
macOS	B-Operating_System
supports	O
Unix	B-Application
symbolic	O
(	O
and	O
hard	O
)	O
links	O
as	O
well	O
.	O
</s>
<s>
An	O
alias	B-Application
acts	O
as	O
a	O
stand-in	O
for	O
any	O
object	O
in	O
the	O
file	B-Application
system	I-Application
,	O
such	O
as	O
a	O
document	O
,	O
an	O
application	B-Application
,	O
a	O
folder	O
,	O
a	O
hard	B-Device
disk	I-Device
,	O
a	O
network	B-General_Concept
share	I-General_Concept
or	O
removable	O
medium	O
or	O
a	O
printer	O
.	O
</s>
<s>
Likewise	O
,	O
choosing	O
an	O
alias	B-Application
file	O
from	O
within	O
a	O
'	O
File	O
Open	O
 '	O
dialog	O
box	O
would	O
open	O
the	O
original	O
file	O
.	O
</s>
<s>
The	O
purpose	O
of	O
an	O
alias	B-Application
is	O
to	O
assist	O
the	O
user	O
in	O
managing	O
large	O
numbers	O
of	O
files	O
by	O
providing	O
alternative	O
ways	O
to	O
access	O
them	O
without	O
having	O
to	O
copy	O
the	O
files	O
themselves	O
.	O
</s>
<s>
While	O
a	O
typical	O
alias	B-Application
under	O
the	O
classic	B-Application
Mac	I-Application
OS	I-Application
was	O
small	O
,	O
between	O
1	O
and	O
5KB	O
,	O
under	O
macOS	B-Operating_System
it	O
can	O
be	O
fairly	O
large	O
,	O
more	O
than	O
5MB	O
(	O
5000KB	O
)	O
for	O
the	O
alias	B-Application
to	O
a	O
folder	O
.	O
</s>
<s>
An	O
alias	B-Application
is	O
a	O
dynamic	O
reference	O
to	O
an	O
object	O
.	O
</s>
<s>
The	O
original	O
may	O
be	O
moved	O
to	O
another	O
place	O
within	O
the	O
same	O
filesystem	B-Application
,	O
without	O
breaking	O
the	O
link	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
stores	O
several	O
pieces	O
of	O
information	O
about	O
the	O
original	O
in	O
the	O
resource	B-Operating_System
fork	I-Operating_System
of	O
the	O
alias	B-Application
file	O
.	O
</s>
<s>
This	O
fault-tolerance	O
sets	O
the	O
alias	B-Application
apart	O
from	O
similar	O
functions	O
in	O
some	O
other	O
operating	B-General_Concept
systems	I-General_Concept
,	O
such	O
as	O
the	O
Unix	B-Application
symbolic	B-Application
link	I-Application
or	O
the	O
Microsoft	B-Application
Windows	I-Application
shortcut	O
,	O
at	O
the	O
expense	O
of	O
increased	O
complexity	O
and	O
unpredictability	O
.	O
</s>
<s>
For	O
example	O
,	O
an	O
application	B-Application
can	O
be	O
moved	O
from	O
one	O
directory	O
to	O
another	O
within	O
the	O
same	O
filesystem	B-Application
,	O
but	O
an	O
existing	O
alias	B-Application
would	O
still	O
launch	O
the	O
same	O
application	B-Application
when	O
double-clicked	O
.	O
</s>
<s>
The	O
question	O
can	O
arise	O
of	O
how	O
an	O
alias	B-Application
should	O
work	O
if	O
a	O
file	O
is	O
moved	O
,	O
and	O
then	O
a	O
file	O
is	O
created	O
with	O
the	O
same	O
name	O
as	O
the	O
original	O
moved	O
file	O
,	O
since	O
the	O
alias	B-Application
can	O
be	O
used	O
to	O
locate	O
both	O
the	O
original	O
name	O
and	O
the	O
new	O
location	O
of	O
the	O
original	O
file	O
.	O
</s>
<s>
With	O
symbolic	B-Application
links	I-Application
the	O
reference	O
is	O
unambiguous	O
(	O
soft	B-Application
links	I-Application
refer	O
to	O
the	O
new	O
file	O
,	O
hard	B-Application
links	I-Application
to	O
the	O
original	O
)	O
.	O
</s>
<s>
Before	O
Mac	O
OS	O
X	O
10.2	O
,	O
however	O
,	O
such	O
an	O
ambiguous	O
alias	B-Application
would	O
consistently	O
find	O
the	O
original	O
moved	O
file	O
,	O
rather	O
than	O
the	O
recreated	O
file	O
.	O
</s>
<s>
In	O
Mac	O
OS	O
X	O
10.2	O
and	O
later	O
releases	O
,	O
the	O
new	O
file	O
is	O
found	O
,	O
matching	O
the	O
behaviour	O
of	O
symbolic	B-Application
links	I-Application
.	O
</s>
<s>
macOS	B-Operating_System
applications	O
can	O
programmatically	O
use	O
the	O
old	O
behavior	O
if	O
required	O
.	O
</s>
<s>
Aliases	O
are	O
similar	O
in	O
operation	O
to	O
shadows	O
in	O
the	O
graphical	O
Workplace	B-Device
Shell	I-Device
of	O
the	O
OS/2	B-Application
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
In	O
System	B-Operating_System
7	I-Operating_System
through	O
Mac	B-Operating_System
OS	I-Operating_System
9	I-Operating_System
,	O
aliases	O
distinguished	O
themselves	O
visually	O
to	O
the	O
user	O
by	O
the	O
fact	O
that	O
their	O
file	O
names	O
were	O
in	O
italics	O
.	O
</s>
<s>
To	O
accommodate	O
languages	O
that	O
do	O
n't	O
have	O
italics	O
(	O
such	O
as	O
Japanese	O
)	O
,	O
in	O
Mac	B-Operating_System
OS	I-Operating_System
8.5	I-Operating_System
another	O
distinguishing	O
mark	O
was	O
added	O
,	O
badging	O
with	O
an	O
"	O
alias	B-Application
arrow	O
"	O
—	O
a	O
black	O
arrow	O
with	O
a	O
small	O
white	O
border	O
—	O
similar	O
to	O
that	O
used	O
for	O
shortcuts	O
in	O
Microsoft	B-Application
Windows	I-Application
.	O
</s>
<s>
In	O
macOS	B-Operating_System
,	O
the	O
filenames	O
of	O
aliases	O
are	O
not	O
italicized	O
,	O
but	O
the	O
arrow	O
badge	O
remains	O
.	O
</s>
<s>
The	O
alias	B-Application
files	O
in	O
macOS	B-Operating_System
start	O
by	O
the	O
magic	O
number	O
62	O
6F	O
6F	O
6B	O
00	O
00	O
00	O
00	O
6D	O
61	O
72	O
6B	O
00	O
00	O
00	O
00	O
which	O
is	O
in	O
ASCII	B-Protocol
book␀␀␀␀mark␀␀␀␀	O
( ␀	O
representing	O
the	O
Null	O
character	O
)	O
.	O
</s>
<s>
Following	O
the	O
magic	O
number	O
,	O
it	O
has	O
been	O
reported	O
that	O
an	O
alias	B-Application
has	O
a	O
set	O
of	O
records	O
inside	O
it	O
,	O
each	O
record	O
is	O
150	O
bytes	O
long	O
and	O
consists	O
of	O
the	O
fields	O
shown	O
below	O
(	O
all	O
integers	O
are	O
big	O
endian	O
)	O
.	O
</s>
<s>
However	O
,	O
alias	B-Application
files	O
are	O
far	O
larger	O
than	O
this	O
would	O
explain	O
,	O
and	O
include	O
other	O
information	O
at	O
least	O
including	O
icons	O
.	O
</s>
<s>
The	O
following	O
is	O
for	O
use	O
with	O
the	O
Apple	O
's	O
Alias	B-Application
Resource	O
Manager	O
.	O
</s>
<s>
In	O
System	B-Operating_System
7	I-Operating_System
,	O
the	O
only	O
way	O
to	O
create	O
an	O
alias	B-Application
was	O
to	O
select	O
the	O
original	O
and	O
choose	O
"	O
Make	O
Alias	B-Application
"	O
from	O
the	O
"	O
File	O
"	O
menu	O
.	O
</s>
<s>
An	O
alias	B-Application
,	O
with	O
the	O
same	O
name	O
and	O
"	O
alias	B-Application
"	O
appended	O
would	O
then	O
be	O
created	O
in	O
the	O
same	O
folder	O
.	O
</s>
<s>
In	O
later	O
versions	O
,	O
it	O
became	O
possible	O
to	O
create	O
aliases	O
by	O
drag-and-drop	O
,	O
while	O
holding	O
down	O
the	O
command	B-Device
and	O
option	B-Device
modifier	O
keys	O
.	O
</s>
<s>
Mac	B-Operating_System
OS	I-Operating_System
8.5	I-Operating_System
added	O
a	O
feature	O
for	O
re-connecting	O
aliases	O
that	O
had	O
been	O
broken	O
for	O
one	O
reason	O
or	O
another	O
(	O
when	O
the	O
simple	O
search	O
algorithms	O
failed	O
to	O
find	O
a	O
reliable	O
replacement	O
)	O
.	O
</s>
<s>
In	O
Mac	B-Operating_System
OS	I-Operating_System
8.5	I-Operating_System
options	O
were	O
added	O
for	O
command-option	O
dragging	O
an	O
object	O
in	O
the	O
Finder	O
to	O
create	O
an	O
alias	B-Application
at	O
that	O
location	O
.	O
</s>
<s>
This	O
is	O
where	O
the	O
alias	B-Application
cursor	O
was	O
added	O
to	O
the	O
system	O
.	O
</s>
<s>
The	O
Alias	B-Application
Manager	O
API	O
is	O
part	O
of	O
Carbon	B-Operating_System
.	O
</s>
<s>
It	O
is	O
unknown	O
whether	O
it	O
was	O
present	O
in	O
Mac	B-Application
OS	I-Application
Classic	I-Application
.	O
</s>
<s>
Mac	O
OS	O
X	O
10.6	O
introduced	O
some	O
alias-related	O
APIs	O
to	O
Cocoa	B-Operating_System
,	O
as	O
a	O
part	O
of	O
.	O
</s>
<s>
Unix	B-Application
and	O
similar	O
operating	B-General_Concept
systems	I-General_Concept
provide	O
2	O
features	O
very	O
similar	O
to	O
macOS	B-Operating_System
aliases	O
:	O
symbolic	B-Application
links	I-Application
and	O
hard	B-Application
links	I-Application
.	O
</s>
<s>
When	O
using	O
the	O
macOS	B-Operating_System
Finder	O
,	O
links	O
are	O
displayed	O
and	O
treated	O
largely	O
like	O
macOS	B-Operating_System
aliases	O
,	O
and	O
even	O
carry	O
an	O
identical	O
"	O
Kind	O
"	O
attribute	O
.	O
</s>
<s>
However	O
,	O
when	O
using	O
the	O
shell	O
command	B-Device
line	O
,	O
macOS	B-Operating_System
aliases	O
are	O
not	O
recognized	O
:	O
for	O
example	O
,	O
you	O
cannot	O
use	O
the	O
cd	O
command	B-Device
with	O
the	O
name	O
of	O
an	O
alias	B-Application
file	O
.	O
</s>
<s>
This	O
is	O
because	O
an	O
alias	B-Application
is	O
implemented	O
as	O
a	O
file	O
on	O
the	O
disk	O
that	O
must	O
be	O
interpreted	O
by	O
an	O
API	O
while	O
links	O
are	O
implemented	O
within	O
the	O
filesystem	B-Application
and	O
are	O
thus	O
functional	O
at	O
any	O
level	O
of	O
the	O
OS	O
.	O
</s>
<s>
There	O
is	O
currently	O
no	O
pre-installed	O
command	B-Device
to	O
resolve	O
an	O
alias	B-Application
to	O
the	O
path	O
of	O
the	O
file	O
or	O
directory	O
it	O
refers	O
to	O
.	O
</s>
<s>
However	O
,	O
a	O
freely	O
available	O
C	O
program	O
makes	O
use	O
of	O
the	O
Mac	O
Carbon	B-Operating_System
APIs	I-Operating_System
to	O
perform	O
this	O
task	O
.	O
</s>
<s>
Given	O
that	O
,	O
commands	O
such	O
as	O
cd	O
can	O
be	O
set	O
up	O
to	O
check	O
for	O
aliases	O
and	O
treat	O
them	O
just	O
like	O
symbolic	O
or	O
hard	B-Application
links	I-Application
.	O
</s>
