<s>
Ctags	B-Device
is	O
a	O
programming	B-Application
tool	I-Application
that	O
generates	O
an	O
index	O
(	O
or	O
tag	O
)	O
file	O
of	O
names	O
found	O
in	O
source	O
and	O
header	O
files	O
of	O
various	O
programming	O
languages	O
to	O
aid	O
code	B-General_Concept
comprehension	I-General_Concept
.	O
</s>
<s>
These	O
tags	O
allow	O
definitions	O
to	O
be	O
quickly	O
and	O
easily	O
located	O
by	O
a	O
text	B-Application
editor	I-Application
,	O
a	O
code	O
search	O
engine	O
,	O
or	O
other	O
utility	O
.	O
</s>
<s>
Alternatively	O
,	O
there	O
is	O
also	O
an	O
output	O
mode	O
that	O
generates	O
a	O
cross	O
reference	O
file	O
,	O
listing	O
information	O
about	O
various	O
names	O
found	O
in	O
a	O
set	O
of	O
language	O
files	O
in	O
human-readable	B-General_Concept
form	O
.	O
</s>
<s>
The	O
original	O
Ctags	B-Device
was	O
introduced	O
in	O
BSD	B-Operating_System
Unix	I-Operating_System
3.0	O
and	O
was	O
written	O
by	O
Ken	O
Arnold	O
,	O
with	O
Fortran	B-Application
support	O
by	O
Jim	O
Kleckner	O
and	O
Pascal	B-Application
support	O
by	O
Bill	O
Joy	O
.	O
</s>
<s>
It	O
is	O
part	O
of	O
the	O
initial	O
release	O
of	O
Single	O
Unix	B-Application
Specification	O
and	O
XPG4	O
of	O
1992	O
.	O
</s>
<s>
Tag	O
index	O
files	O
are	O
supported	O
by	O
many	O
source	B-Application
code	I-Application
editors	I-Application
,	O
including	O
:	O
</s>
<s>
vi	B-Application
(	O
and	O
derivatives	O
such	O
as	O
Elvis	B-Device
,	O
Nvi	B-Device
,	O
Vim	B-Application
,	O
vile	B-Application
,	O
etc	O
.	O
)	O
</s>
<s>
There	O
are	O
a	O
few	O
other	O
implementations	O
of	O
the	O
ctags	B-Device
program	O
:	O
</s>
<s>
GNU	O
Emacs	B-Application
comes	O
with	O
two	O
ctags	B-Device
utilities	O
,	O
etags	O
and	O
ctags	B-Device
,	O
which	O
are	O
compiled	O
from	O
the	O
same	O
source	O
code	O
.	O
</s>
<s>
Etags	O
generates	O
a	O
tag	O
table	O
file	O
for	O
Emacs	B-Application
,	O
while	O
the	O
ctags	B-Device
command	O
is	O
used	O
to	O
create	O
a	O
similar	O
table	O
in	O
a	O
format	O
understood	O
by	O
vi	B-Application
.	O
</s>
<s>
etags	O
does	O
not	O
recognize	O
and	O
ignores	O
options	O
which	O
only	O
make	O
sense	O
for	O
vi	B-Application
style	O
tag	O
files	O
produced	O
by	O
the	O
ctags	B-Device
command	O
.	O
</s>
<s>
Exuberant	O
Ctags	B-Device
,	O
written	O
and	O
maintained	O
by	O
Darren	O
Hiebert	O
until	O
2009	O
,	O
was	O
initially	O
distributed	O
with	O
Vim	B-Application
,	O
but	O
became	O
a	O
separate	O
project	O
upon	O
the	O
release	O
of	O
Vim	B-Application
6	O
.	O
</s>
<s>
It	O
includes	O
support	O
for	O
Emacs	B-Application
and	O
compatibility	O
.	O
</s>
<s>
Exuberant	O
Ctags	B-Device
includes	O
support	O
for	O
over	O
40	O
programming	O
languages	O
with	O
the	O
ability	O
to	O
add	O
support	O
for	O
even	O
more	O
using	O
regular	B-Language
expressions	I-Language
.	O
</s>
<s>
Universal	O
Ctags	B-Device
is	O
a	O
fork	O
of	O
Exuberant	O
Ctags	B-Device
,	O
with	O
the	O
objective	O
of	O
continuing	O
its	O
development	O
.	O
</s>
<s>
creates	O
ctags	B-Device
compatible	O
tag	O
files	O
for	O
Haskell	B-Language
source	O
files	O
.	O
</s>
<s>
It	O
includes	O
support	O
for	O
creating	O
Emacs	B-Application
etags	O
files	O
.	O
</s>
<s>
is	O
a	O
ctags-compatible	O
code	O
indexing	O
solution	O
for	O
JavaScript	B-Language
.	O
</s>
<s>
It	O
is	O
specialized	O
for	O
JavaScript	B-Language
and	O
uses	O
the	O
CommonJS	B-Language
packaging	O
system	O
.	O
</s>
<s>
It	O
outperforms	O
Exuberant	O
Ctags	B-Device
for	O
JavaScript	B-Language
code	O
,	O
finding	O
more	O
tags	O
than	O
the	O
latter	O
.	O
</s>
<s>
The	O
original	O
ctags	B-Device
and	O
the	O
Exuberant/Universal	O
descendants	O
have	O
similar	O
file	O
formats	O
:	O
</s>
<s>
This	O
is	O
the	O
format	O
used	O
by	O
vi	B-Application
and	O
various	O
clones	O
.	O
</s>
<s>
Exactly	O
one	O
tab	O
(	O
)	O
character	O
,	O
although	O
many	O
versions	O
of	O
vi	B-Application
can	O
handle	O
any	O
amount	O
of	O
white	O
space	O
.	O
</s>
<s>
}	O
An	O
ex	B-Device
mode	I-Device
command	O
that	O
will	O
take	O
the	O
editor	O
to	O
the	O
location	O
of	O
the	O
tag	O
.	O
</s>
<s>
For	O
POSIX	O
implementations	O
of	O
vi	B-Application
this	O
may	O
only	O
be	O
a	O
search	O
or	O
a	O
line	O
number	O
,	O
providing	O
added	O
security	O
against	O
arbitrary	O
command	O
execution	O
.	O
</s>
<s>
This	O
is	O
the	O
format	O
used	O
by	O
Vim	B-Application
's	O
Exuberant	O
Ctags	B-Device
and	O
Universal	O
Ctags	B-Device
.	O
</s>
<s>
These	O
programs	O
can	O
generate	O
an	O
original	O
ctags	B-Device
file	O
format	O
or	O
an	O
extended	O
format	O
that	O
attempts	O
to	O
retain	O
backward	O
compatibility	O
.	O
</s>
<s>
The	O
fields	O
up	O
to	O
and	O
including	O
}	O
are	O
the	O
same	O
as	O
for	O
ctags	B-Device
above	O
.	O
</s>
<s>
semicolon	O
+	O
double	O
quote	O
:	O
Ends	O
the	O
}	O
in	O
a	O
way	O
that	O
looks	O
like	O
the	O
start	O
of	O
a	O
comment	O
to	O
vi	B-Application
or	O
ex	B-Device
.	O
</s>
<s>
This	O
format	O
is	O
compatible	O
with	O
non-POSIX	O
vi	B-Application
as	O
the	O
additional	O
data	O
is	O
interpreted	O
as	O
a	O
comment	O
.	O
</s>
<s>
POSIX	O
implementations	O
of	O
vi	B-Application
must	O
be	O
changed	O
to	O
support	O
it	O
,	O
however	O
.	O
</s>
<s>
This	O
is	O
the	O
format	O
used	O
by	O
Emacs	B-Application
etags	O
.	O
</s>
<s>
The	O
tags	O
(	O
ctags	B-Device
)	O
file	O
may	O
look	O
like	O
:	O
</s>
