<s>
Cygwin	B-Language
(	O
)	O
is	O
a	O
Unix-like	B-Operating_System
environment	B-Device
and	O
command-line	B-Application
interface	I-Application
for	O
Microsoft	B-Application
Windows	I-Application
.	O
</s>
<s>
Cygwin	B-Language
's	O
purpose	O
is	O
expressed	O
in	O
its	O
motto	O
:	O
"	O
Get	O
that	O
Linux	B-Application
feeling	O
–	O
on	O
Windows	O
"	O
.	O
</s>
<s>
The	O
terminal	B-Application
emulator	I-Application
Mintty	B-Language
is	O
the	O
default	O
command-line	B-Application
interface	I-Application
provided	O
to	O
interact	O
with	O
the	O
environment	B-Device
.	O
</s>
<s>
The	O
Cygwin	B-Language
installation	O
's	O
directory	O
layout	O
mimics	O
the	O
root	O
file	O
system	O
of	O
Unix-like	B-Operating_System
systems	I-Operating_System
,	O
with	O
directories	O
such	O
as	O
/bin	O
,	O
/home	O
,	O
/etc	O
,	O
/usr	O
,	O
and	O
/var	O
.	O
</s>
<s>
In	O
addition	O
to	O
providing	O
many	O
Unix	B-Application
utilities	O
and	O
a	O
Unix	B-Application
look	B-Application
and	I-Application
feel	I-Application
,	O
Cygwin	B-Language
allows	O
source	O
code	O
designed	O
for	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
to	O
be	O
compiled	O
and	O
run	O
on	O
Windows	O
with	O
minimal	O
modification	O
.	O
</s>
<s>
Cygwin	B-Language
provides	O
native	O
integration	O
of	O
Windows-based	O
applications	O
.	O
</s>
<s>
Thus	O
it	O
is	O
possible	O
to	O
launch	O
Windows	B-Application
applications	I-Application
from	O
the	O
Cygwin	B-Language
environment	B-Device
,	O
as	O
well	O
as	O
to	O
use	O
Cygwin	B-Language
tools	O
and	O
applications	O
within	O
the	O
Windows	O
operating	O
context	O
.	O
</s>
<s>
Cygwin	B-Language
consists	O
of	O
two	O
parts	O
:	O
</s>
<s>
a	O
dynamic-link	O
library	O
(	O
DLL	O
)	O
in	O
the	O
form	O
of	O
a	O
C	B-Language
standard	I-Language
library	I-Language
that	O
acts	O
as	O
a	O
compatibility	B-General_Concept
layer	I-General_Concept
for	O
the	O
POSIX	O
API	B-Application
.	I-Application
</s>
<s>
an	O
extensive	O
collection	O
of	O
software	B-Application
tools	I-Application
and	O
applications	O
that	O
provide	O
a	O
Unix-like	B-Operating_System
look	B-Application
and	I-Application
feel	I-Application
.	O
</s>
<s>
Cygwin	B-Language
is	O
free	B-License
and	I-License
open-source	I-License
software	I-License
,	O
released	O
under	O
the	O
GNU	B-Application
Lesser	I-Application
General	I-Application
Public	I-Application
License	I-Application
version	O
3	O
.	O
</s>
<s>
It	O
was	O
originally	O
developed	O
by	O
Cygnus	O
Solutions	O
,	O
which	O
was	O
later	O
acquired	O
by	O
Red	O
Hat	O
(	O
now	O
part	O
of	O
IBM	O
)	O
,	O
to	O
port	O
the	O
Linux	B-Application
toolchain	B-General_Concept
to	O
Win32	B-Library
,	O
including	O
the	O
GNU	B-Application
Compiler	I-Application
Suite	I-Application
.	O
</s>
<s>
Rather	O
than	O
rewrite	O
the	O
tools	O
to	O
use	O
the	O
Win32	B-Library
runtime	B-Device
environment	I-Device
,	O
Cygwin	B-Language
implemented	O
a	O
POSIX-compatible	O
environment	B-Device
in	O
the	O
form	O
of	O
a	O
dynamic-link	O
library	O
(	O
DLL	O
)	O
.	O
</s>
<s>
The	O
Cygwin	B-Language
environment	B-Device
is	O
provided	O
in	O
two	O
versions	O
;	O
the	O
full	O
64-bit	O
version	O
and	O
a	O
stripped	O
down	O
32-bit	O
version	O
that	O
is	O
slowly	O
being	O
phased	O
out	O
.	O
</s>
<s>
Cygwin	B-Language
consists	O
of	O
a	O
library	O
that	O
implements	O
the	O
POSIX	O
system	O
call	O
API	B-Application
in	O
terms	O
of	O
Windows	O
system	O
calls	O
to	O
enable	O
running	O
of	O
a	O
large	O
number	O
of	O
application	O
programs	O
equivalent	O
to	O
those	O
on	O
Unix	B-Application
systems	I-Application
,	O
and	O
a	O
GNU	B-Operating_System
development	O
toolchain	B-General_Concept
(	O
including	O
GCC	B-Application
and	O
GDB	B-Language
)	O
to	O
allow	O
software	O
development	O
.	O
</s>
<s>
Programmers	O
have	O
ported	O
many	O
Unix	B-Application
,	O
GNU	B-Operating_System
,	O
BSD	B-Operating_System
and	O
Linux	B-Application
programs	O
and	O
packages	O
to	O
Cygwin	B-Language
,	O
including	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
K	B-Language
Desktop	I-Language
Environment	I-Language
3	I-Language
,	O
GNOME	B-Application
,	O
Apache	B-Application
,	O
and	O
TeX	B-Application
.	O
</s>
<s>
Cygwin	B-Language
permits	O
installing	O
inetd	B-Protocol
,	O
syslogd	B-Protocol
,	O
sshd	B-Protocol
,	O
Apache	B-Application
,	O
and	O
other	O
daemons	O
as	O
standard	O
Windows	O
services	O
,	O
allowing	O
Microsoft	B-Application
Windows	I-Application
systems	O
to	O
emulate	O
Unix	B-Application
and	O
Linux	B-Application
servers	O
.	O
</s>
<s>
Cygwin	B-Language
programs	O
are	O
installed	O
by	O
running	O
Cygwin	B-Language
's	O
"	O
setup	O
"	O
program	O
,	O
which	O
downloads	O
the	O
necessary	O
program	O
and	O
feature	O
package	O
files	O
from	O
repositories	O
on	O
the	O
Internet	O
.	O
</s>
<s>
As	O
mentioned	O
,	O
there	O
are	O
two	O
versions	O
of	O
this	O
setup	O
program	O
,	O
one	O
for	O
32-bit	O
versions	O
of	O
the	O
Cygwin	B-Language
DLL	O
,	O
and	O
corresponding	O
applications	O
,	O
and	O
one	O
for	O
64-bit	O
versions	O
.	O
</s>
<s>
Efforts	O
to	O
reconcile	O
concepts	O
that	O
differ	O
between	O
Unix	B-Application
and	O
Windows	O
systems	O
include	O
:	O
</s>
<s>
A	O
Cygwin-specific	O
version	O
of	O
the	O
Unix	B-Application
mount	O
command	O
allows	O
mounting	B-Application
Windows	O
paths	O
as	O
"	O
filesystems	O
"	O
in	O
the	O
Unix	B-Application
file	O
space	O
.	O
</s>
<s>
Initial	O
mount-points	O
can	O
be	O
configured	O
in	O
/etc/fstab	B-Protocol
,	O
which	O
has	O
a	O
format	O
very	O
similar	O
to	O
Unix	B-Application
systems	I-Application
,	O
except	O
that	O
Windows	O
paths	O
appear	O
in	O
place	O
of	O
devices	O
.	O
</s>
<s>
Cygwin	B-Language
1.7	O
introduced	O
comprehensive	O
support	O
for	O
POSIX	O
locales	B-Device
and	O
many	O
character	B-General_Concept
encodings	I-General_Concept
,	O
whereby	O
the	O
UTF-8	O
Unicode	O
encoding	O
became	O
the	O
default	O
.	O
</s>
<s>
Windows	O
drive	O
letters	O
map	O
to	O
a	O
special	O
directory	O
,	O
so	O
for	O
example	O
C	B-Language
:	O
appears	O
as	O
/cygdrive/c	O
.	O
</s>
<s>
Windows	O
paths	O
can	O
also	O
be	O
used	O
directly	O
from	O
Cygwin	B-Language
programs	O
,	O
but	O
many	O
programs	O
do	O
not	O
support	O
them	O
correctly	O
,	O
hence	O
this	O
is	O
discouraged	O
.	O
</s>
<s>
Full-featured	O
/dev	B-Application
and	O
/proc	B-Application
file-systems	O
are	O
provided	O
.	O
</s>
<s>
/proc/registry	O
provides	O
direct	O
filesystem	O
access	O
to	O
the	O
registry	O
.	O
</s>
<s>
Cygwin	B-Language
supports	O
POSIX	O
symbolic	B-Application
links	I-Application
,	O
representing	O
them	O
as	O
plain-text	O
files	O
with	O
the	O
system	O
attribute	O
set	O
.	O
</s>
<s>
Cygwin	B-Language
1.5	O
represented	O
them	O
as	O
Windows	B-Protocol
Explorer	I-Protocol
shortcuts	O
,	O
but	O
this	O
was	O
changed	O
for	O
reasons	O
of	O
performance	O
and	O
POSIX	O
correctness	O
.	O
</s>
<s>
Cygwin	B-Language
also	O
recognises	O
NTFS	O
junction	O
points	O
and	O
symbolic	B-Application
links	I-Application
and	O
treats	O
them	O
as	O
POSIX	O
symbolic	B-Application
links	I-Application
,	O
but	O
it	O
does	O
not	O
create	O
them	O
as	O
their	O
semantics	O
are	O
not	O
fully	O
POSIX-compliant	O
.	O
</s>
<s>
The	O
POSIX	O
API	B-Application
for	O
handling	O
access	O
control	O
lists	O
(	O
ACLs	O
)	O
is	O
supported	O
and	O
maps	O
to	O
the	O
Windows	O
NT	O
ACL	O
system	O
.	O
</s>
<s>
Special	O
formats	O
of	O
/etc/passwd	O
and	O
/etc/group	O
are	O
provided	O
that	O
include	O
pointers	O
to	O
the	O
Windows	O
equivalent	O
SIDs	O
(	O
in	O
the	O
Gecos	B-Operating_System
field	I-Operating_System
)	O
,	O
allowing	O
for	O
mapping	O
between	O
Unix	B-Application
and	O
Windows	O
users	O
and	O
groups	O
.	O
</s>
<s>
The	O
fork	B-Language
system	O
call	O
for	O
duplicating	O
a	O
process	O
is	O
fully	O
implemented	O
,	O
but	O
it	O
does	O
not	O
map	O
well	O
to	O
the	O
Windows	B-Library
API	I-Library
.	O
</s>
<s>
For	O
example	O
,	O
the	O
copy-on-write	B-Language
optimization	O
strategy	O
could	O
not	O
be	O
used	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
Cygwin	B-Language
's	O
fork	B-Language
is	O
rather	O
slow	O
compared	O
with	O
Linux	B-Application
and	O
others	O
.	O
</s>
<s>
(	O
That	O
overhead	O
can	O
often	O
be	O
avoided	O
by	O
replacing	O
uses	O
of	O
the	O
fork/exec	B-Operating_System
technique	O
with	O
calls	O
to	O
the	O
spawn	B-Language
functions	O
declared	O
in	O
the	O
Windows-specific	O
process.h	B-Language
header	O
)	O
.	O
</s>
<s>
The	O
Cygwin	B-Language
DLL	O
contains	O
a	O
console	O
driver	O
that	O
emulates	O
a	O
Unix-style	B-Operating_System
terminal	B-Application
within	O
the	O
Windows	B-Application
console	I-Application
.	O
</s>
<s>
Cygwin	B-Language
's	O
default	O
user	O
interface	O
is	O
the	O
bash	B-Operating_System
shell	I-Operating_System
running	O
in	O
the	O
Cygwin	B-Language
console	O
.	O
</s>
<s>
The	O
DLL	O
also	O
implements	O
pseudo	B-Protocol
terminal	I-Protocol
(	O
pty	O
)	O
devices	O
.	O
</s>
<s>
Cygwin	B-Language
ships	O
with	O
a	O
number	O
of	O
terminal	B-Application
emulators	I-Application
that	O
are	O
based	O
on	O
them	O
,	O
including	O
mintty	B-Language
,	O
rxvt(-unicode )	O
,	O
and	O
xterm	B-Language
.	O
</s>
<s>
These	O
are	O
more	O
compliant	O
with	O
Unix	B-Application
terminal	B-Application
standards	O
and	O
user	O
interface	O
conventions	O
than	O
the	O
Cygwin	B-Language
console	O
,	O
but	O
are	O
less	O
suited	O
for	O
running	O
Windows	B-Application
console	I-Application
programs	O
.	O
</s>
<s>
Various	O
utilities	O
are	O
provided	O
for	O
converting	O
between	O
Windows	O
and	O
Unix	B-Application
paths	O
and	O
file	O
formats	O
,	O
for	O
handling	O
line	O
ending	O
(	O
CRLF/LF	O
)	O
issues	O
,	O
for	O
displaying	O
the	O
DLLs	O
that	O
an	O
executable	O
is	O
linked	O
with	O
,	O
etc	O
.	O
</s>
<s>
Apart	O
from	O
always	O
being	O
linked	O
against	O
the	O
Cygwin	B-Language
DLL	O
,	O
Cygwin	B-Language
executables	O
are	O
normal	O
Windows	O
executables	O
.	O
</s>
<s>
This	O
means	O
that	O
Cygwin	B-Language
programs	O
have	O
full	O
access	O
to	O
the	O
Windows	B-Library
API	I-Library
and	O
other	O
Windows	O
libraries	O
,	O
which	O
allows	O
gradual	O
porting	O
of	O
programs	O
from	O
one	O
platform	O
to	O
the	O
other	O
.	O
</s>
<s>
The	O
version	O
of	O
gcc	B-Application
that	O
comes	O
with	O
Cygwin	B-Language
has	O
various	O
extensions	O
for	O
creating	O
Windows	O
DLLs	O
,	O
specifying	O
whether	O
a	O
program	O
is	O
a	O
windowing	O
or	O
console-mode	O
program	O
,	O
adding	O
resources	O
,	O
etc	O
.	O
</s>
<s>
Support	O
for	O
compiling	O
programs	O
that	O
do	O
not	O
require	O
the	O
POSIX	O
compatibility	B-General_Concept
layer	I-General_Concept
provided	O
by	O
the	O
Cygwin	B-Language
DLL	O
used	O
to	O
be	O
included	O
in	O
the	O
default	O
gcc	B-Application
,	O
but	O
is	O
provided	O
by	O
cross-compilers	B-Application
contributed	O
by	O
the	O
MinGW-w64	O
project	O
.	O
</s>
<s>
Cygwin	B-Language
is	O
used	O
heavily	O
for	O
porting	O
many	O
popular	O
pieces	O
of	O
software	O
to	O
the	O
Windows	O
platform	O
.	O
</s>
<s>
It	O
is	O
used	O
to	O
compile	O
Sun	O
Java	B-Language
,	O
LibreOffice	B-Application
,	O
and	O
even	O
web	O
server	O
software	O
like	O
Lighttpd	B-Protocol
and	O
Hiawatha	B-Application
.	O
</s>
<s>
The	O
Cygwin	B-Language
API	B-Application
library	O
is	O
licensed	O
under	O
the	O
GNU	B-Application
Lesser	I-Application
General	I-Application
Public	I-Application
License	I-Application
version	O
3	O
(	O
or	O
later	O
)	O
with	O
an	O
exception	O
to	O
allow	O
linking	O
to	O
any	O
free	B-License
and	I-License
open-source	I-License
software	I-License
whose	O
license	O
conforms	O
to	O
the	B-License
Open	I-License
Source	I-License
Definition	I-License
(	O
less	O
strict	O
than	O
the	O
Free	O
Software	O
Definition	O
)	O
.	O
</s>
<s>
Cygwin	B-Language
began	O
in	O
1995	O
as	O
a	O
project	O
of	O
Steve	O
Chamberlain	O
,	O
a	O
Cygnus	O
engineer	O
who	O
observed	O
that	O
Windows	O
NT	O
and	O
95	O
used	O
COFF	O
as	O
their	O
object	B-Application
file	I-Application
format	I-Application
,	O
and	O
that	O
GNU	B-Operating_System
already	O
included	O
support	O
for	O
x86	B-Operating_System
and	O
COFF	O
,	O
and	O
the	O
C	B-Language
library	I-Language
newlib	B-Language
.	O
</s>
<s>
He	O
thought	O
it	O
would	O
be	O
possible	O
to	O
retarget	O
GCC	B-Application
and	O
produce	O
a	O
cross	B-Application
compiler	I-Application
generating	O
executables	O
that	O
could	O
run	O
on	O
Windows	O
.	O
</s>
<s>
The	O
next	O
step	O
was	O
to	O
attempt	O
to	O
bootstrap	B-Application
the	O
compiler	O
on	O
a	O
Windows	O
system	O
,	O
requiring	O
sufficient	O
emulation	O
of	O
Unix	B-Application
to	O
let	O
the	O
GNU	B-Application
configure	I-Application
shell	B-Language
script	I-Language
run	O
.	O
</s>
<s>
A	O
Bourne	O
shell-compatible	O
command	O
interpreter	O
,	O
such	O
as	O
bash	B-Operating_System
,	O
was	O
needed	O
and	O
in	O
turn	O
a	O
fork	B-Language
system	O
call	O
emulation	O
and	O
standard	B-Operating_System
input/output	I-Operating_System
.	O
</s>
<s>
Windows	O
includes	O
similar	O
functionality	O
,	O
so	O
the	O
Cygwin	B-Language
library	O
just	O
needed	O
to	O
provide	O
a	O
POSIX-compatible	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
and	O
properly	O
translate	O
calls	O
and	O
manage	O
private	O
versions	O
of	O
data	O
,	O
such	O
as	O
file	B-Application
descriptors	I-Application
.	O
</s>
<s>
Initially	O
,	O
Cygwin	B-Language
was	O
called	O
gnuwin32	B-Language
(	O
not	O
to	O
be	O
confused	O
with	O
the	O
current	O
GnuWin32	B-Language
project	O
)	O
.	O
</s>
<s>
When	O
Microsoft	O
registered	O
the	O
trademark	O
Win32	B-Library
,	O
the	O
32	O
was	O
dropped	O
to	O
simply	O
become	O
Cygwin	B-Language
.	O
</s>
<s>
By	O
1996	O
,	O
other	O
engineers	O
had	O
joined	O
in	O
,	O
because	O
it	O
was	O
clear	O
that	O
Cygwin	B-Language
would	O
be	O
a	O
useful	O
way	O
to	O
provide	O
Cygnus	O
 '	O
embedded	O
tools	O
hosted	O
on	O
Windows	O
systems	O
(	O
the	O
previous	O
strategy	O
had	O
been	O
to	O
use	O
DJGPP	B-Application
)	O
.	O
</s>
<s>
It	O
was	O
especially	O
attractive	O
because	O
it	O
was	O
possible	O
to	O
do	O
a	O
three-way	B-Application
cross-compile	I-Application
,	O
for	O
instance	O
to	O
use	O
a	O
hefty	O
Sun	O
Microsystems	O
workstation	O
to	O
build	O
,	O
say	O
,	O
a	O
Windows-x-MIPS	O
cross-compiler	B-Application
,	O
which	O
was	O
faster	O
than	O
using	O
the	O
PC	O
at	O
the	O
time	O
.	O
</s>
<s>
In	O
1999	O
,	O
Cygnus	O
offered	O
Cygwin	B-Language
1.0	O
as	O
a	O
commercial	O
product	O
of	O
interest	O
in	O
its	O
own	O
right	O
although	O
subsequent	O
versions	O
have	O
not	O
been	O
released	O
,	O
instead	O
relying	O
on	O
continued	O
open	O
source	O
releases	O
.	O
</s>
<s>
From	O
June	O
23	O
,	O
2016	O
the	O
Cygwin	B-Language
library	O
version	O
2.5.2	O
was	O
licensed	O
under	O
the	O
GNU	B-Application
Lesser	I-Application
General	I-Application
Public	I-Application
License	I-Application
(	O
LGPL	B-Application
)	O
version	O
3	O
,	O
so	O
is	O
now	O
possible	O
to	O
link	O
against	O
closed	O
source	O
applications	O
.	O
</s>
<s>
Before	O
this	O
was	O
available	O
there	O
were	O
two	O
possibilities	O
:	O
to	O
release	O
the	O
source	O
code	O
of	O
the	O
application	O
or	O
buy	O
a	O
Cygwin	B-Language
license	O
to	O
release	O
a	O
closed	O
source	O
application	O
.	O
</s>
<s>
Cygwin	B-Language
's	O
base	O
package	O
selection	O
is	O
fairly	O
small	O
(	O
about	O
100MB	O
)	O
,	O
containing	O
little	O
more	O
than	O
the	O
bash	B-Operating_System
(	O
interactive	O
user	O
)	O
and	O
dash	B-Operating_System
(	O
installation	O
)	O
shells	O
and	O
the	O
core	O
file	O
and	O
text	O
manipulation	O
utilities	O
expected	O
of	O
a	O
Unix	B-Application
command	B-Application
line	I-Application
.	O
</s>
<s>
Additional	O
packages	O
are	O
available	O
as	O
optional	O
installs	O
from	O
within	O
the	O
Cygwin	B-Language
Setup	O
program	O
and	O
package	O
manager	O
(	O
"	O
setup-x86_64.exe	O
"	O
–	O
64bit	O
)	O
.	O
</s>
<s>
The	O
Cygwin/X	B-Application
project	O
contributes	O
an	O
implementation	O
of	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
that	O
allows	O
graphical	O
Unix	B-Application
programs	O
to	O
display	O
their	O
user	O
interfaces	O
on	O
the	O
Windows	O
desktop	O
.	O
</s>
<s>
Cygwin/X	B-Application
supports	O
over	O
500	O
packages	O
including	O
major	O
X	B-Operating_System
window	I-Operating_System
managers	O
,	O
desktop	O
environments	O
,	O
and	O
applications	O
,	O
for	O
example	O
:	O
</s>
<s>
In	O
addition	O
to	O
the	O
low-level	O
Xlib/XCB	B-Language
libraries	O
for	O
developing	O
X	B-Operating_System
applications	O
,	O
Cygwin	B-Language
ships	O
with	O
various	O
higher-level	O
and	O
cross-platform	O
GUI	B-Application
frameworks	O
,	O
including	O
GTK+	B-Application
and	O
Qt	B-Language
.	O
</s>
<s>
The	O
Cygwin	B-Language
Ports	O
project	O
provided	O
many	O
additional	O
packages	O
that	O
were	O
not	O
available	O
in	O
the	O
Cygwin	B-Language
distribution	O
itself	O
.	O
</s>
<s>
Examples	O
included	O
GNOME	B-Application
and	O
K	B-Language
Desktop	I-Language
Environment	I-Language
3	I-Language
as	O
well	O
as	O
the	O
MySQL	B-Application
database	O
and	O
the	O
PHP	B-Application
scripting	O
language	O
.	O
</s>
<s>
Most	O
ports	O
have	O
been	O
adopted	O
by	O
volunteer	O
maintainers	O
as	O
Cygwin	B-Language
packages	O
,	O
and	O
Cygwin	B-Language
Ports	O
are	O
no	O
longer	O
maintained	O
.	O
</s>
