<s>
In	O
computing	O
,	O
is	O
a	O
command	B-Application
to	O
search	O
the	O
man	B-Protocol
page	I-Protocol
files	O
in	O
Unix	B-Application
and	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
Apropos	B-Device
takes	O
its	O
name	O
from	O
the	O
French	O
"	O
à	O
propos	O
"	O
(	O
Latin	O
"	O
ad	O
prōpositum	O
"	O
)	O
which	O
means	O
about	O
.	O
</s>
<s>
Often	O
a	O
wrapper	O
for	O
the	O
command	B-Application
,	O
the	O
apropos	B-Device
command	B-Application
is	O
used	O
to	O
search	O
the	O
"	O
name	O
"	O
sections	O
of	O
all	O
manual	B-Protocol
pages	I-Protocol
for	O
the	O
string/s	O
(	O
called	O
keyword/s	O
)	O
specified	O
.	O
</s>
<s>
The	O
output	O
is	O
a	O
list	O
of	O
all	O
manual	B-Protocol
pages	I-Protocol
containing	O
the	O
search	O
term	O
in	O
their	O
name	O
or	O
description	O
.	O
</s>
<s>
This	O
is	O
often	O
useful	O
if	O
one	O
knows	O
the	O
action	O
that	O
is	O
desired	O
,	O
but	O
does	O
not	O
remember	O
the	O
exact	O
command	B-Application
or	O
page	O
name	O
.	O
</s>
<s>
apropos	B-Device
search	O
is	O
case	O
insensitive	O
.	O
</s>
<s>
usually	O
searches	O
in	O
a	O
precompiled	O
database	O
that	O
is	O
shared	O
with	O
,	O
a	O
command	B-Application
for	O
obtaining	O
the	O
brief	O
description	O
of	O
a	O
specific	O
command	B-Application
whose	O
exact	O
name	O
is	O
already	O
known	O
.	O
</s>
<s>
The	O
following	O
example	O
demonstrates	O
the	O
output	O
of	O
the	O
command	B-Application
:	O
</s>
<s>
In	O
this	O
example	O
,	O
is	O
used	O
to	O
search	O
for	O
the	O
keyword	O
"	O
mount	O
"	O
,	O
and	O
returns	O
the	O
indicated	O
man	B-Protocol
pages	I-Protocol
that	O
include	O
the	O
term	O
"	O
mount	O
"	O
.	O
</s>
<s>
The	O
following	O
example	O
demonstrates	O
the	O
output	O
of	O
the	O
command	B-Application
with	O
an	O
regexp	O
keyword	O
(	O
abc.n	O
)	O
and	O
a	O
regular	O
keyword	O
:	O
</s>
<s>
"	O
abc.n	O
"	O
and	O
xzless	O
,	O
and	O
returns	O
the	O
indicated	O
man	B-Protocol
pages	I-Protocol
that	O
include	O
the	O
keywords	O
.	O
</s>
<s>
is	O
a	O
command	B-Application
for	O
obtaining	O
the	O
brief	O
description	O
of	O
a	O
specific	O
command	B-Application
whose	O
exact	O
name	O
is	O
already	O
known	O
.	O
</s>
<s>
On	O
systems	O
with	O
mandoc	B-Application
,	O
it	O
is	O
a	O
wrapper	O
for	O
(	O
search	O
by	O
name	O
only	O
)	O
.	O
</s>
<s>
is	O
a	O
command	B-Application
for	O
indexing	O
all	O
on-disk	O
manuals	O
into	O
a	O
database	O
that	O
and	O
can	O
read	O
from	O
.	O
</s>
<s>
is	O
a	O
command	B-Application
that	O
performs	O
the	O
same	O
function	O
in	O
man-db	B-Protocol
.	O
</s>
<s>
The	O
database	O
is	O
traditionally	O
plain	O
text	O
,	O
but	O
man-db	B-Protocol
,	O
the	O
implementation	O
found	O
on	O
many	O
Linux	B-Application
distributions	I-Application
,	O
use	O
a	O
Berkeley	B-Language
DB	I-Language
instead	O
.	O
</s>
<s>
The	O
mandoc	B-Application
implementation	O
used	O
on	O
many	O
BSD	O
distributions	O
likewise	O
has	O
its	O
own	O
innovations	O
on	O
the	O
format	O
.	O
</s>
