<s>
Almquist	B-Operating_System
shell	I-Operating_System
(	O
also	O
known	O
as	O
A	O
Shell	O
,	O
ash	B-Operating_System
and	O
sh	O
)	O
is	O
a	O
lightweight	O
Unix	B-Application
shell	I-Application
originally	O
written	O
by	O
Kenneth	O
Almquist	O
in	O
the	O
late	O
1980s	O
.	O
</s>
<s>
Initially	O
a	O
clone	O
of	O
the	O
System	O
V.4	O
variant	O
of	O
the	B-Device
Bourne	I-Device
shell	I-Device
,	O
it	O
replaced	O
the	O
original	O
Bourne	B-Device
shell	I-Device
in	O
the	O
BSD	B-Operating_System
versions	O
of	O
Unix	O
released	O
in	O
the	O
early	O
1990s	O
.	O
</s>
<s>
ash	B-Operating_System
was	O
first	O
released	O
via	O
a	O
posting	O
to	O
the	O
Usenet	B-Application
news	I-Application
group	O
,	O
approved	O
and	O
moderated	O
by	O
Rich	B-Application
Salz	I-Application
on	O
30	O
May	O
1989	O
.	O
</s>
<s>
Fast	O
,	O
small	O
,	O
and	O
virtually	O
compatible	O
with	O
the	O
POSIX	O
standard	O
's	O
specification	O
of	O
the	O
Unix	B-Application
shell	I-Application
,	O
ash	B-Operating_System
did	O
not	O
provide	O
line	B-Application
editing	I-Application
or	O
command	B-Application
history	I-Application
mechanisms	O
,	O
because	O
Almquist	O
felt	O
that	O
such	O
functionality	O
should	O
be	O
moved	O
into	O
the	O
terminal	B-General_Concept
driver	B-Application
.	O
</s>
<s>
The	O
following	O
is	O
extracted	O
from	O
the	O
ash	B-Operating_System
package	O
information	O
from	O
Slackware	B-Application
v14	O
:	O
</s>
<s>
Myriad	O
forks	O
have	O
been	O
produced	O
from	O
the	O
original	O
ash	B-Operating_System
release	O
.	O
</s>
<s>
These	O
derivatives	O
of	O
ash	B-Operating_System
are	O
installed	O
as	O
the	O
default	O
shell	O
(	O
/bin/sh	B-Device
)	O
on	O
FreeBSD	B-Operating_System
,	O
NetBSD	B-Device
,	O
DragonFly	B-Application
BSD	I-Application
,	O
MINIX	B-Operating_System
,	O
and	O
in	O
some	O
Linux	B-Application
distributions	I-Application
.	O
</s>
<s>
MINIX	B-Operating_System
3.2	O
used	O
the	O
original	O
ash	B-Operating_System
version	O
,	O
whose	O
test	B-Application
feature	O
differed	O
from	O
POSIX	O
.	O
</s>
<s>
That	O
version	O
of	O
the	O
shell	O
was	O
replaced	O
in	O
MINIX	B-Operating_System
3.3	O
.	O
</s>
<s>
Android	B-Application
used	O
ash	B-Operating_System
until	O
Android	B-Application
4.0	I-Application
,	O
at	O
which	O
point	O
it	O
switched	O
to	O
mksh	B-Language
.	O
</s>
<s>
In	O
1997	O
Herbert	O
Xu	O
ported	O
ash	B-Operating_System
from	O
NetBSD	B-Device
to	O
Debian	O
Linux	B-Application
.	O
</s>
<s>
In	O
September	O
2002	O
,	O
with	O
release	O
0.4.1	O
,	O
this	O
port	O
was	O
renamed	O
to	O
Dash	O
(	O
Debian	B-Operating_System
Almquist	I-Operating_System
shell	I-Operating_System
)	O
.	O
</s>
<s>
Like	O
its	O
predecessor	O
,	O
Dash	O
implements	O
support	O
for	O
neither	O
internationalization	B-General_Concept
and	I-General_Concept
localization	I-General_Concept
nor	O
multi-byte	O
character	O
encoding	O
(	O
both	O
required	O
in	O
POSIX	O
)	O
.	O
</s>
<s>
Line	B-Application
editing	I-Application
and	O
history	O
support	O
based	O
on	O
GNU	B-Application
Readline	I-Application
is	O
optional	O
(	O
)	O
.	O
</s>
<s>
Because	O
of	O
its	O
slimness	O
,	O
Ubuntu	B-Operating_System
decided	O
to	O
adopt	O
Dash	O
as	O
the	O
default	O
/bin/sh	B-Device
in	O
2006	O
.	O
</s>
<s>
The	O
reason	O
for	O
using	O
Dash	O
is	O
faster	O
shell	B-Language
script	I-Language
execution	O
,	O
especially	O
during	O
startup	O
of	O
the	O
operating	O
system	O
,	O
compared	O
to	O
previous	O
versions	O
of	O
Debian	O
and	O
Ubuntu	B-Operating_System
that	O
used	O
Bash	B-Operating_System
for	O
this	O
purpose	O
,	O
although	O
Bash	B-Operating_System
is	O
still	O
the	O
default	O
login	O
shell	O
for	O
interactive	O
use	O
.	O
</s>
<s>
Dash	O
became	O
the	O
default	O
/bin/sh	B-Device
in	O
Ubuntu	B-Operating_System
starting	O
with	O
the	O
6.10	O
release	O
in	O
October	O
2006	O
.	O
</s>
<s>
Dash	O
replaced	O
Bash	B-Operating_System
and	O
became	O
the	O
default	O
/bin/sh	B-Device
in	O
Debian	O
6	O
(	O
Squeeze	O
)	O
.	O
</s>
<s>
A	O
result	O
of	O
the	O
shift	O
is	O
that	O
many	O
shell	B-Language
scripts	I-Language
were	O
found	O
making	O
use	O
of	O
Bash-specific	O
functionalities	O
(	O
"	O
bashisms	O
"	O
)	O
without	O
properly	O
declaring	O
it	O
in	O
the	O
shebang	B-Operating_System
line	I-Operating_System
.	O
</s>
<s>
The	O
problem	O
was	O
first	O
spotted	O
in	O
Ubuntu	B-Operating_System
and	O
the	O
Ubuntu	B-Operating_System
maintainers	O
decided	O
to	O
make	O
all	O
the	O
scripts	O
comply	O
with	O
the	O
POSIX	O
standard	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
all	O
scripts	O
in	O
Debian	O
and	O
Ubuntu	B-Operating_System
are	O
guaranteed	O
to	O
be	O
POSIX-compliant	O
,	O
save	O
for	O
the	O
extensions	O
merged	O
into	O
Dash	O
for	O
convenience	O
(	O
,	O
,	O
)	O
.	O
</s>
<s>
A	O
similar	O
transition	O
has	O
happened	O
in	O
Slackware	B-Application
Linux	I-Application
,	O
although	O
their	O
version	O
of	O
is	O
only	O
partially	O
based	O
on	O
Dash	O
.	O
</s>
<s>
Ash	B-Operating_System
(	O
mainly	O
the	O
Dash	O
fork	O
)	O
is	O
also	O
fairly	O
popular	O
in	O
embedded	B-Application
Linux	I-Application
systems	O
.	O
</s>
<s>
Dash	O
version	O
0.3.8-5	O
was	O
incorporated	O
into	O
BusyBox	B-Application
,	O
the	O
catch-all	O
executable	O
often	O
employed	O
in	O
this	O
area	O
,	O
and	O
is	O
used	O
in	O
distributions	O
like	O
DSLinux	O
,	O
Alpine	O
Linux	B-Application
,	O
Tiny	O
Core	O
Linux	B-Application
and	O
Linux-based	O
router	B-Protocol
firmware	O
such	O
as	O
OpenWrt	B-Application
,	O
Tomato	B-Protocol
and	O
DD-WRT	B-Protocol
.	O
</s>
