<s>
ptx	B-Device
is	O
a	O
Unix	B-Application
utility	I-Application
,	O
named	O
after	O
the	O
permuted	O
index	O
algorithm	O
which	O
it	O
uses	O
to	O
produce	O
a	O
search	O
or	O
concordance	O
report	O
in	O
the	O
Keyword	O
in	O
Context	O
(	O
KWIC	O
)	O
format	O
.	O
</s>
<s>
It	O
is	O
available	O
on	O
most	O
Unix	B-Application
and	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
(	O
e.g.	O
</s>
<s>
Linux	B-Application
,	O
FreeBSD	B-Operating_System
)	O
.	O
</s>
<s>
The	O
GNU	B-Operating_System
implementation	O
uses	O
extensions	O
that	O
are	O
more	O
powerful	O
than	O
the	O
older	O
SysV	B-Operating_System
implementation	O
.	O
</s>
<s>
The	O
command	B-Application
is	O
available	O
as	O
a	O
separate	O
package	O
for	O
Microsoft	B-Application
Windows	I-Application
as	O
part	O
of	O
the	O
UnxUtils	B-Application
collection	O
of	O
native	B-Language
Win32	B-Library
ports	O
of	O
common	O
GNU	B-Operating_System
Unix-like	B-Operating_System
utilities	O
.	O
</s>
<s>
There	O
is	O
also	O
a	O
corresponding	O
IBM	B-Device
mainframe	I-Device
utility	O
which	O
performs	O
the	O
same	O
function	O
.	O
</s>
