<s>
In	O
a	O
Unix	B-Application
shell	I-Application
,	O
the	O
full	O
stop	O
called	O
the	O
dot	B-Device
command	B-Application
(	O
.	O
)	O
</s>
<s>
is	O
a	O
command	B-Application
that	O
evaluates	O
commands	O
in	O
a	O
computer	B-Operating_System
file	I-Operating_System
in	O
the	O
current	O
execution	O
context	O
.	O
</s>
<s>
In	O
C	B-Operating_System
Shell	I-Operating_System
,	O
a	O
similar	O
functionality	O
is	O
provided	O
as	O
the	O
source	O
command	B-Application
,	O
and	O
this	O
name	O
is	O
seen	O
in	O
"	O
extended	O
"	O
POSIX	O
shells	O
as	O
well	O
.	O
</s>
<s>
The	O
dot	B-Device
command	B-Application
is	O
not	O
to	O
be	O
confused	O
with	O
a	O
dot	B-Application
file	I-Application
,	O
which	O
is	O
a	O
dot-prefixed	O
hidden	B-Application
file	I-Application
or	I-Application
hidden	I-Application
directory	I-Application
.	O
</s>
<s>
Nor	O
is	O
it	O
to	O
be	O
confused	O
with	O
the	O
./scriptfile	O
notation	O
for	O
running	O
commands	O
,	O
which	O
is	O
simply	O
a	O
relative	O
path	B-Application
pointing	O
to	O
the	O
current	O
directory	B-Application
(	O
notated	O
in	O
Unix	O
as	O
a	O
'	O
.	O
'	O
</s>
<s>
character	O
,	O
and	O
typically	O
outside	O
of	O
the	O
Path	B-Application
variable	I-Application
)	O
.	O
</s>
<s>
The	O
filename	B-Device
is	O
the	O
dot	B-Device
command	B-Application
's	O
first	O
argument	O
.	O
</s>
<s>
When	O
this	O
argument	O
does	O
not	O
contain	O
a	O
slash	O
,	O
the	O
shell	O
will	O
search	O
for	O
the	O
file	O
in	O
all	O
directories	B-Application
defined	O
in	O
the	O
PATH	B-Application
environment	O
variable	O
.	O
</s>
<s>
Unlike	O
normal	O
commands	O
which	O
are	O
also	O
found	O
in	O
PATH	B-Application
,	O
the	O
file	O
to	O
source	O
does	O
not	O
have	O
to	O
be	O
executable	B-Application
.	O
</s>
<s>
Otherwise	O
the	O
filename	B-Device
is	O
considered	O
as	O
a	O
simple	O
path	B-Application
to	O
the	O
file	O
.	O
</s>
<s>
In	O
several	O
"	O
extended	O
"	O
shells	O
including	O
bash	B-Operating_System
,	O
zsh	O
and	O
ksh	O
,	O
one	O
may	O
specify	O
parameters	O
in	O
a	O
second	O
argument	O
.	O
</s>
<s>
This	O
is	O
very	O
different	O
from	O
scripts	O
run	O
directly	O
by	O
shebang	B-Operating_System
or	O
as	O
sh	O
foo.sh,	O
which	O
are	O
run	O
in	O
a	O
new	O
,	O
separate	O
process	O
space	O
,	O
with	O
a	O
separate	O
environment	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
dot	B-Device
command	B-Application
can	O
be	O
used	O
for	O
splitting	O
a	O
big	O
script	O
into	O
smaller	O
pieces	O
,	O
potentially	O
enabling	O
modular	B-Architecture
design	O
.	O
</s>
<s>
source	O
is	O
a	O
shell-builtin	O
command	B-Application
that	O
evaluates	O
the	O
file	O
following	O
the	O
command	B-Application
,	O
as	O
a	O
list	O
of	O
commands	O
,	O
executed	O
in	O
the	O
current	O
context	O
.	O
</s>
<s>
The	O
source	O
command	B-Application
can	O
be	O
abbreviated	O
as	O
just	O
a	O
dot	B-Device
(	O
.	O
)	O
</s>
<s>
in	O
Bash	B-Operating_System
and	O
similar	O
POSIX-ish	O
shells	O
.	O
</s>
<s>
However	O
,	O
this	O
is	O
not	O
acceptable	O
in	O
C	B-Operating_System
shell	I-Operating_System
,	O
where	O
the	O
command	B-Application
first	O
appeared	O
.	O
</s>
<s>
Some	O
Bash	B-Operating_System
scripts	I-Operating_System
should	O
be	O
run	O
using	O
the	O
source	O
your-script	O
syntax	O
rather	O
than	O
run	O
as	O
an	O
executable	B-Application
command	B-Application
,	O
e.g.	O
,	O
if	O
they	O
contain	O
a	O
change	B-Application
directory	I-Application
(	O
cd	B-Application
)	O
command	B-Application
and	O
the	O
user	O
intends	O
that	O
they	O
be	O
left	O
in	O
that	O
directory	B-Application
after	O
the	O
script	O
is	O
complete	O
,	O
or	O
they	O
contain	O
an	O
export	O
command	B-Application
and	O
the	O
user	O
wants	O
to	O
modify	O
the	O
environment	O
of	O
the	O
current	O
shell	O
.	O
</s>
<s>
Passing	O
the	O
script	O
filename	B-Device
to	O
the	O
desired	O
shell	O
will	O
run	O
the	O
script	O
in	O
a	O
subshell	B-Operating_System
,	O
not	O
the	O
current	O
context	O
.	O
</s>
