<s>
A	O
command	B-Operating_System
shell	O
is	O
a	O
command-line	B-Application
interface	I-Application
to	O
interact	O
with	O
and	O
manipulate	O
a	O
computer	O
's	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
UNIX	B-Application
,	O
Text-based	B-Application
CLIBourne	O
shell	O
current	O
versionVarious	O
UNIXsh1977SunOS-5.x	O
,	O
FreeBSD	B-Operating_System
(	O
non-root	O
user	O
)	O
SunOS-5.xText-based	O
CLISince	O
mid	O
1990s.if	O
compiled	O
with	O
-DACCT.POSIX	O
shellPOSIXsh1992As	O
part	O
of	O
IEEE	O
Std.1003.2-1992	O
(	O
POSIX.2	O
)	O
;	O
integrated	O
into	O
IEEE	O
Std.1003.1	O
with	O
the	O
2001	O
revision.POSIXText-based	O
CLIUnspecified	O
(	O
given	O
as	O
an	O
example	O
)	O
bash	B-Operating_System
(	O
v4	O
)	O
POSIXbash	O
,	O
sh1989GNU	O
,	O
Linux	B-Application
(	O
default	O
for	O
root	O
)	O
,	O
macOS	O
10.3	O
–	O
10.14GNU	O
,	O
Linux	B-Application
,	O
Haiku	B-Language
,	O
macOS	O
10.3	O
–	O
10.14Text-based	O
CLI	B-Application
,	O
"	O
Bash	B-Operating_System
now	O
supports	O
the	O
\u	O
and	O
\U	O
Unicode	O
escape	O
.	O
</s>
<s>
"	O
cshPOSIXcsh1978SunOSText-based	O
CLItcshPOSIXtcsh	O
,	O
csh1983FreeBSD	O
(	O
default	O
for	O
root	O
)	O
,	O
formerly	O
Mac	B-Application
OS	I-Application
XText-based	O
CLIHamilton	O
C	O
shellWin32	O
,	O
OS/2csh1988	O
(	O
OS/2	B-Application
version	O
no	O
longer	O
maintained	O
)	O
Text-based	B-Application
CLIScshPOSIXscsh1994ksh	O
(	O
ksh93t+	O
)	O
POSIXksh1983AIX	O
,	O
HP-UXOpenSolarisText-based	O
CLIpdkshPOSIXksh	O
,	O
sh1989	O
?	O
OpenBSDDefault	O
shell	O
in	O
OpenBSD	B-Operating_System
is	O
ksh	B-Language
(	O
pdksh	O
)	O
.OpenBSDText-based	O
CLIzshPOSIXzsh1990Deepin	O
,	O
GoboLinux	O
,	O
Grml	B-Language
,	O
macOS	O
10.15	O
+	O
,	O
Kali	O
2020.4	O
+Grml	O
,	O
macOS	O
10.15	O
+	O
Text-based	B-Application
CLIashPOSIXsh1989Minix	O
,	O
BusyBox	B-Application
based	O
systemsNetBSD	O
,	O
Minix	B-Operating_System
,	O
BusyBox	B-Application
based	O
systemsText-based	O
CLI	B-Application
(	O
for	O
BusyBox	B-Application
,	O
supported	O
in	O
command-line	B-Application
editing	O
,	O
but	O
not	O
in	O
string	O
handling	O
)	O
CCPCP/M	O
,	O
MP/M	B-Operating_System
( CCP	O
)	O
1976	O
(	O
1974	O
)	O
CP/M	B-Application
(	O
no	O
login	O
)	O
,	O
MP/MCP/M	O
,	O
MP/M	B-Operating_System
(	O
originally	O
closed-source	O
)	O
Text-based	B-Application
CLI	B-Application
(	O
automatic	O
via	O
)	O
(	O
only	O
via	O
external	O
command	B-Operating_System
to	O
update	O
)	O
COMMAND.COMDOSCOMMAND1980	O
(	O
3rd	O
party	O
implementations	O
,	O
not	O
bound	O
to	O
a	O
specific	O
DOS	B-Device
vendor	O
or	O
version	O
,	O
available	O
)	O
DOS	B-Device
,	O
Windows	B-Application
95	I-Application
,	O
98	B-Device
,	O
SE	O
,	O
MEDOS	O
,	O
Windows	B-Application
95	I-Application
,	O
98	B-Device
,	O
SE	O
,	O
MEvendor	O
specific	O
,	O
f.e.	O
</s>
<s>
MS-EULA	O
,	O
MS-DOS	O
and	O
Windows	B-Application
component	O
–	O
covered	O
by	O
a	O
valid	O
license	O
for	O
MS-DOS	O
or	O
Microsoft	B-Application
Windows	I-Application
.	O
</s>
<s>
or	O
BSD/GPL	O
(	O
free	O
clones	O
)	O
(	O
except	O
for	O
OpenDOS	O
,	O
DR-DOS	B-Application
,	O
PTS/DOS	O
and	O
FreeDOS	O
)	O
Text-based	B-Application
CLI	B-Application
(	O
except	O
for	O
DR-DOS	B-Application
)	O
(	O
via	O
or	O
)	O
(	O
via	O
startup	O
parameters	O
and	O
environment	O
variables	O
,	O
DR-DOS	B-Application
also	O
supports	O
user-default	O
switch	O
command	B-Operating_System
)	O
(	O
automatic	O
for	O
primary	O
shell	O
,	O
or	O
explicitly	O
via	O
,	O
or	O
startup	O
options	O
)	O
(	O
via	O
command	B-Operating_System
or	O
and	O
startup	O
options	O
)	O
OS/2	B-Application
CMD.EXEOS/2	O
,	O
eComStation	B-Device
,	O
ArcaOSCMD1987OS/2	O
,	O
eComStation	B-Device
,	O
ArcaOSOS/2	O
,	O
eComStation	B-Device
,	O
ArcaOSOS/2	O
component	O
–	O
covered	O
by	O
a	O
valid	O
license	O
for	O
OS/2.Text	O
-based	O
CLI	B-Application
(	O
only	O
via	O
startup	O
option	O
)	O
(	O
via	O
command	B-Operating_System
or	O
and	O
startup	O
options	O
)	O
Windows	B-Application
CMD.EXECommand	O
extensions	O
enabled	O
,	O
or	O
"	O
CMD	B-Device
/X	O
"	O
.Win32CMD1993Windows	O
NT	O
,	O
2000	O
,	O
XP	O
,	O
Server	O
2003	O
,	O
VistaWindows	O
NT	O
,	O
2000	O
,	O
XP	O
,	O
Server	O
2003	O
,	O
VistaWindows	O
component	O
–	O
covered	O
by	O
a	O
valid	O
license	O
for	O
Microsoft	O
Windows.Text-based	O
CLI	B-Application
(	O
for	O
UTF-8	O
,	O
but	O
program	O
arguments	O
are	O
still	O
encoded	O
in	O
local	O
codepage	O
)	O
(	O
via	O
registry	O
,	O
startup	O
parameters	O
,	O
and	O
environment	O
variables	O
)	O
(	O
automatic	O
via	O
registry	O
,	O
or	O
explicitly	O
via	O
startup	O
option	O
)	O
(	O
via	O
command	B-Operating_System
or	O
and	O
startup	O
options	O
)	O
4DOS	B-Application
,	O
NDOSDOS	O
,	O
Windows	B-Application
95	I-Application
,	O
98	B-Device
,	O
SE	O
,	O
ME4DOS	O
,	O
NDOS1989	O
(	O
1986	O
)	O
Text-based	B-Application
CLI	B-Application
with	O
TUI	B-Application
extensions	O
(	O
popups	O
,	O
help	O
system	O
,	O
internal	O
variable	O
,	O
command	B-Operating_System
)	O
(	O
via	O
,	O
except	O
for	O
,	O
,	O
,	O
,	O
,	O
,	O
,	O
commands	O
and	O
file	O
/	O
directory	O
coloring	O
)	O
(	O
via	O
/	O
file	O
,	O
startup	O
parameters	O
,	O
environment	O
variables	O
,	O
command	B-Operating_System
)	O
(	O
automatic	O
for	O
primary	O
shell	O
and	O
/	O
as	O
well	O
as	O
/	O
for	O
any	O
shell	O
,	O
or	O
explicitly	O
via	O
,	O
or	O
startup	O
options	O
)	O
(	O
via	O
command	B-Operating_System
or	O
and	O
startup	O
options	O
)	O
4OS2OS/2	O
,	O
eComStation	B-Device
,	O
ArcaOS4OS21992	O
(	O
but	O
bundled	O
with	O
ArcaOS	B-Device
)	O
Text-based	B-Application
CLI	B-Application
(	O
via	O
file	O
,	O
startup	O
parameters	O
,	O
environment	O
variables	O
,	O
command	B-Operating_System
)	O
(	O
automatic	O
via	O
/	O
as	O
well	O
as	O
/	O
files	O
,	O
or	O
explicitly	O
via	O
option	O
)	O
(	O
via	O
command	B-Operating_System
or	O
and	O
startup	O
options	O
)	O
TCC	B-Application
(	O
formerly	O
4NT	B-Application
)	O
Win32TCC1993optionaloptionalText-based	O
CLI	B-Application
(	O
Take	B-Application
Command	I-Application
:	O
GUI	B-Application
)	O
(	O
console	O
mouse	O
,	O
popups	O
,	O
help	O
system	O
,	O
,	O
internal	O
variables	O
,	O
command	B-Operating_System
)	O
(	O
via	O
registry	O
,	O
/	O
file	O
,	O
startup	O
parameters	O
,	O
environment	O
variables	O
,	O
command	B-Operating_System
)	O
(	O
automatic	O
via	O
registry	O
and	O
/	O
as	O
well	O
as	O
/	O
,	O
or	O
explicitly	O
via	O
startup	O
option	O
)	O
(	O
via	O
command	B-Operating_System
or	O
and	O
startup	O
options	O
)	O
VMS	B-Operating_System
DCLOpenVMSAutomatically	O
for	O
login/interactive	O
process1977	O
?	O
VMSVMSProprietary	O
,	O
bundled	O
in	O
VMSText-based	O
CLIPowerShell.NET	O
,.	O
NET	O
FrameworkPowerShell2006Windows	O
10	O
,	O
8	O
,	O
Server	O
2008	O
,	O
7Microsoft	O
PowerShell	B-Application
is	O
installed	O
by	O
default	O
on	O
Windows	B-Application
7	O
and	O
later	O
.	O
</s>
<s>
ShellCommandnamecompletionPathcompletionCommandargumentcompletionWildcardcompletionCommandhistoryMandatoryargumentpromptAutomaticsuggestionsColoreddirectorylistingsTexthighlightingSyntaxhighlightingDirectory	O
history	B-Device
,	O
stack	O
or	O
similar	O
featuresImplicitdirectorychangeAuto­	O
correctionIntegratedenvironmentSnippetsValuepromptMenu/optionspromptProgressindicatorContextsensitivehelpCommandbuilderThompson	O
shell	O
?	O
</s>
<s>
?	O
Bourne	B-Device
shell	I-Device
1977	O
version	O
?	O
</s>
<s>
?	O
Bourne	B-Device
shell	I-Device
current	O
versioncurrent	O
versions	O
from	O
Jörg	O
Schilling	O
.	O
</s>
<s>
?	O
ksh	B-Language
(	O
ksh93t+	O
)	O
pdkshzshThis	O
applies	O
only	O
on	O
reserved	O
words	O
and	O
other	O
syntactic	O
features.zsh	O
does	O
not	O
feature	O
syntax	O
highlighting	O
,	O
but	O
a	O
3rd	O
party	O
project	O
exists	O
which	O
offers	O
this	O
capability	O
as	O
an	O
add-on	O
:	O
zsh-syntax-highlightingashCCPCOMMAND.COMAvailable	O
through	O
the	O
add-on.Available	O
in	O
DR-DOS	B-Application
through	O
.	O
</s>
<s>
(	O
only	O
in	O
DR-DOS	B-Application
through	O
%$ON%	O
,	O
%$OFF%	O
,	O
%$HEADER%	O
,	O
%$FOOTER%	O
)	O
(	O
only	O
single-stepping	O
with	O
COMMAND	B-Operating_System
/Y	O
)	O
(	O
only	O
via	O
external	O
command	B-Operating_System
,	O
in	O
DR-DOS	B-Application
also	O
via	O
/	O
internal	O
commands	O
)	O
OS/2CMD.EXEWindowsCMD.EXE	O
(	O
via	O
command	B-Operating_System
)	O
4DOSAlternatively	O
available	O
through	O
the	O
add-on	O
as	O
well.Alternatively	O
available	O
in	O
DR-DOS	B-Application
through	O
as	O
well	O
.	O
</s>
<s>
(	O
via	O
,	O
and	O
commands	O
)	O
(	O
via	O
function	O
,	O
and	O
indirectly	O
via	O
a	O
combination	O
of	O
,	O
,	O
commands	O
)	O
(	O
except	O
for	O
command	B-Operating_System
for	O
INI	O
file	O
directives	O
)	O
4OS2	B-Application
??????	O
</s>
<s>
?	O
TCC	B-Application
(	O
formerly	O
4NT	B-Application
)	O
(	O
via	O
,	O
,	O
and	O
commands	O
)	O
(	O
via	O
function	O
,	O
and	O
indirectly	O
via	O
a	O
combination	O
of	O
,	O
,	O
commands	O
)	O
TCC	B-Application
has	O
special	O
prompt	O
functions	O
for	O
Yes	O
,	O
No	O
,	O
Cancel	O
,	O
Close	O
,	O
Retry.PowerShellYes	O
,	O
in	O
PSReadLine	O
moduleYes	O
,	O
in	O
ISEYes	O
,	O
in	O
ISEThe	O
$	O
host.ui.PromptForChoice	O
function	O
allows	O
for	O
a	O
menu-style	O
prompt	O
for	O
choices	O
.	O
</s>
<s>
the	O
progress	O
bar	O
is	O
displayed	O
on	O
the	O
console	O
of	O
the	O
controlling	O
session	O
,	O
not	O
as	O
part	O
of	O
the	O
regular	O
output.	O
,	O
in	O
ISEThe	O
cmdlet	O
inspects	O
the	O
command	B-Operating_System
definition	O
and	O
opens	O
an	O
interactive	O
windows	B-Application
with	O
a	O
named	O
input	O
field	O
for	O
each	O
parameter/switch	O
,	O
in	O
ISErcHandled	O
by	O
rio	B-Language
,	O
GNU	B-Application
readline	I-Application
,	O
editline	O
or	O
vrl.	O
??	O
BeanShell	B-Language
?	O
</s>
<s>
?	O
VMS	B-Operating_System
DCL	I-Operating_System
?	O
</s>
<s>
Background	O
execution	O
allows	O
a	O
shell	O
to	O
run	O
a	O
command	B-Operating_System
without	O
user	O
interaction	O
in	O
the	O
terminal	O
,	O
freeing	O
the	O
command	B-Application
line	I-Application
for	O
additional	O
work	O
with	O
the	O
shell	O
.	O
</s>
<s>
POSIX	O
shells	O
and	O
other	O
Unix	B-Application
shells	O
allow	O
background	O
execution	O
by	O
using	O
the	O
&	O
character	O
at	O
the	O
end	O
of	O
command	B-Operating_System
.	O
</s>
<s>
In	O
PowerShell	B-Application
,	O
the	O
Start-Process	O
or	O
Start-Job	O
cmdlets	O
can	O
be	O
used	O
.	O
</s>
<s>
Completion	O
features	O
assist	O
the	O
user	O
in	O
typing	O
commands	O
at	O
the	O
command	B-Application
line	I-Application
,	O
by	O
looking	O
for	O
and	O
suggesting	O
matching	O
words	O
for	O
incomplete	O
ones	O
.	O
</s>
<s>
Command	B-Operating_System
name	O
completion	O
is	O
the	O
completion	O
of	O
the	O
name	O
of	O
a	O
command	B-Operating_System
.	O
</s>
<s>
In	O
most	O
shells	O
,	O
a	O
command	B-Operating_System
can	O
be	O
a	O
program	O
in	O
the	O
command	B-Operating_System
path	O
(	O
usually	O
$PATH	O
)	O
,	O
a	O
builtin	O
command	B-Operating_System
,	O
a	O
function	O
or	O
alias	O
.	O
</s>
<s>
Bash	B-Operating_System
,	O
zsh	B-Application
,	O
and	O
fish	B-Language
have	O
completion	O
for	O
all	O
variable	O
names	O
.	O
</s>
<s>
PowerShell	B-Application
has	O
completions	O
for	O
environment	O
variable	O
names	O
,	O
shell	O
variable	O
names	O
and	O
—	O
from	O
within	O
user-defined	O
functions	O
—	O
parameter	O
names	O
.	O
</s>
<s>
Command	B-Operating_System
argument	O
completion	O
is	O
the	O
completion	O
of	O
a	O
specific	O
command	B-Operating_System
's	O
arguments	O
.	O
</s>
<s>
Bash	B-Operating_System
,	O
zsh	B-Application
and	O
fish	B-Language
offer	O
parameter	O
name	O
completion	O
through	O
a	O
definition	O
external	O
to	O
the	O
command	B-Operating_System
,	O
distributed	O
in	O
a	O
separate	O
completion	O
definition	O
file	O
.	O
</s>
<s>
For	O
command	B-Operating_System
parameter	O
name/value	O
completions	O
,	O
these	O
shells	O
assume	O
path/filename	O
completion	O
if	O
no	O
completion	O
is	O
defined	O
for	O
the	O
command	B-Operating_System
.	O
</s>
<s>
The	O
fish	B-Language
shell	I-Language
additionally	O
supports	O
parsing	O
of	O
man	B-Protocol
pages	I-Protocol
to	O
extract	O
parameter	O
information	O
that	O
can	O
be	O
used	O
to	O
improve	O
completions/suggestions	O
.	O
</s>
<s>
In	O
PowerShell	B-Application
,	O
all	O
types	O
of	O
commands	O
(	O
cmdlets	O
,	O
functions	O
,	O
script	O
files	O
)	O
inherently	O
expose	O
data	O
about	O
the	O
names	O
,	O
types	O
and	O
valid	O
value	O
ranges/lists	O
for	O
each	O
argument	O
.	O
</s>
<s>
This	O
metadata	O
is	O
used	O
by	O
PowerShell	B-Application
to	O
automatically	O
support	O
argument	O
name	O
and	O
value	O
completion	O
for	O
built-in	O
commands/functions	O
,	O
user-defined	O
commands/functions	O
as	O
well	O
as	O
for	O
script	O
files	O
.	O
</s>
<s>
Support	O
for	O
command	B-Operating_System
history	B-Device
means	O
that	O
a	O
user	O
can	O
recall	O
a	O
previous	O
command	B-Operating_System
into	O
the	O
command-line	B-Application
editor	O
and	O
edit	O
it	O
before	O
issuing	O
the	O
potentially	O
modified	O
command	B-Operating_System
.	O
</s>
<s>
Shells	O
that	O
support	O
completion	O
may	O
also	O
be	O
able	O
to	O
directly	O
complete	O
the	O
command	B-Operating_System
from	O
the	O
command	B-Operating_System
history	B-Device
given	O
a	O
partial/initial	O
part	O
of	O
the	O
previous	O
command	B-Operating_System
.	O
</s>
<s>
Most	O
modern	O
shells	O
support	O
command	B-Operating_System
history	B-Device
.	O
</s>
<s>
Shells	O
which	O
support	O
command	B-Operating_System
history	B-Device
in	O
general	O
also	O
support	O
completion	O
from	O
history	B-Device
rather	O
than	O
just	O
recalling	O
commands	O
from	O
the	O
history	B-Device
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
plain	O
command	B-Operating_System
text	O
,	O
PowerShell	B-Application
also	O
records	O
execution	O
start	O
-	O
and	O
end	O
time	O
and	O
execution	O
status	O
in	O
the	O
command	B-Operating_System
history	B-Device
.	O
</s>
<s>
Mandatory	O
arguments/parameters	O
are	O
arguments/parameters	O
which	O
must	O
be	O
assigned	O
a	O
value	O
upon	O
invocation	O
of	O
the	O
command	B-Operating_System
,	O
function	O
or	O
script	O
file	O
.	O
</s>
<s>
A	O
shell	O
that	O
can	O
determine	O
ahead	O
of	O
invocation	O
that	O
there	O
are	O
missing	O
mandatory	O
values	O
,	O
can	O
assist	O
the	O
interactive	O
user	O
by	O
prompting	O
for	O
those	O
values	O
instead	O
of	O
letting	O
the	O
command	B-Operating_System
fail	O
.	O
</s>
<s>
Having	O
the	O
shell	O
prompt	O
for	O
missing	O
values	O
will	O
allow	O
the	O
author	O
of	O
a	O
script	O
,	O
command	B-Operating_System
or	O
function	O
to	O
mark	O
a	O
parameter	O
as	O
mandatory	O
instead	O
of	O
creating	O
script	O
code	O
to	O
either	O
prompt	O
for	O
the	O
missing	O
values	O
(	O
after	O
determining	O
that	O
it	O
is	O
being	O
run	O
interactively	O
)	O
or	O
fail	O
with	O
a	O
message	O
.	O
</s>
<s>
PowerShell	B-Application
allows	O
commands	O
,	O
functions	O
and	O
scripts	O
to	O
define	O
arguments/parameters	O
as	O
mandatory	O
.	O
</s>
<s>
Shells	O
featuring	O
automatic	O
suggestions	O
display	O
optional	O
command-line	B-Application
completions	O
as	O
the	O
user	O
types	O
.	O
</s>
<s>
The	O
PowerShell	B-Application
and	O
fish	B-Language
shells	I-Language
natively	O
support	O
this	O
feature	O
;	O
pressing	O
the	O
key	O
inserts	O
the	O
completion	O
.	O
</s>
<s>
Implementations	O
of	O
this	O
feature	O
can	O
differ	O
between	O
shells	O
;	O
for	O
example	O
,	O
PowerShell	B-Application
and	O
zsh	B-Application
use	O
an	O
external	O
module	O
to	O
provide	O
completions	O
,	O
and	O
fish	B-Language
derives	O
its	O
completions	O
from	O
the	O
user	O
's	O
command	B-Operating_System
history	B-Device
.	O
</s>
<s>
Shells	O
may	O
record	O
a	O
history	B-Device
of	O
directories	O
the	O
user	O
has	O
been	O
in	O
and	O
allow	O
for	O
fast	O
switching	O
to	O
any	O
recorded	O
location	O
.	O
</s>
<s>
The	O
concept	O
had	O
been	O
realized	O
as	O
early	O
as	O
1978	O
in	O
the	O
release	O
of	O
the	B-Operating_System
C	I-Operating_System
shell	I-Operating_System
(	O
csh	B-Operating_System
)	O
.	O
</s>
<s>
PowerShell	B-Application
allows	O
multiple	O
named	O
stacks	O
to	O
be	O
used	O
.	O
</s>
<s>
Unlike	O
most	O
other	O
shells	O
,	O
PowerShell	B-Application
's	O
location	O
concept	O
allow	O
location	O
stacks	O
to	O
hold	O
file	O
system	O
locations	O
as	O
well	O
as	O
other	O
location	O
types	O
like	O
e.g.	O
</s>
<s>
Active	B-Protocol
Directory	I-Protocol
organizational	O
units/groups	O
,	O
SQL	B-Application
Server	I-Application
databases/tables/objects	O
,	O
Internet	B-Application
Information	I-Application
Server	I-Application
applications/sites/virtual	O
directories	O
.	O
</s>
<s>
Command	B-Application
line	I-Application
interpreters	O
4DOS	B-Application
and	O
its	O
graphical	O
successor	O
Take	B-Application
Command	I-Application
Console	I-Application
also	O
feature	O
a	O
directory	O
stack	O
.	O
</s>
<s>
A	O
directory	O
name	O
can	O
be	O
used	O
directly	O
as	O
a	O
command	B-Operating_System
which	O
implicitly	O
changes	O
the	O
current	O
location	O
to	O
the	O
directory	O
.	O
</s>
<s>
This	O
must	O
be	O
distinguished	O
from	O
an	O
unrelated	O
load	O
drive	O
feature	O
supported	O
by	O
Concurrent	B-Operating_System
DOS	I-Operating_System
,	O
Multiuser	B-Operating_System
DOS	I-Operating_System
,	O
System	O
Manager	O
and	O
REAL/32	B-Operating_System
,	O
where	O
the	O
drive	O
letter	O
L	O
:	O
will	O
be	O
implicitly	O
updated	O
to	O
point	O
to	O
the	O
load	O
path	O
of	O
a	O
loaded	O
application	O
,	O
thereby	O
allowing	O
applications	O
to	O
refer	O
to	O
files	O
residing	O
in	O
their	O
load	O
directory	O
under	O
a	O
standardized	O
drive	O
letter	O
instead	O
of	O
under	O
an	O
absolute	O
path	O
.	O
</s>
<s>
When	O
a	O
command	B-Application
line	I-Application
does	O
not	O
match	O
a	O
command	B-Operating_System
or	O
arguments	O
directly	O
,	O
spell	O
checking	O
can	O
automatically	O
correct	O
common	O
typing	O
mistakes	O
(	O
such	O
as	O
case	O
sensitivity	O
,	O
missing	O
letters	O
)	O
.	O
</s>
<s>
There	O
are	O
two	O
approaches	O
to	O
this	O
;	O
the	O
shell	O
can	O
either	O
suggest	O
probable	O
corrections	O
upon	O
command	B-Operating_System
invocation	O
,	O
or	O
this	O
can	O
happen	O
earlier	O
as	O
part	O
of	O
a	O
completion	O
or	O
autosuggestion	O
.	O
</s>
<s>
The	O
tcsh	B-Language
and	O
zsh	B-Application
shells	O
feature	O
optional	O
spell	O
checking/correction	O
,	O
upon	O
command	B-Operating_System
invocation	O
.	O
</s>
<s>
Fish	B-Language
does	O
the	O
autocorrection	O
upon	O
completion	O
and	O
autosuggestion	O
.	O
</s>
<s>
The	O
feature	O
is	O
therefore	O
not	O
in	O
the	O
way	O
when	O
typing	O
out	O
the	O
whole	O
command	B-Operating_System
and	O
pressing	O
enter	O
,	O
whereas	O
extensive	O
use	O
of	O
the	O
tab	O
and	O
right-arrow	O
keys	O
makes	O
the	O
shell	O
mostly	O
case	O
insensitive	O
.	O
</s>
<s>
The	O
PSReadLine	O
PowerShell	B-Application
module	O
(	O
which	O
is	O
shipped	O
with	O
version	O
5.0	O
)	O
provides	O
the	O
option	O
to	O
specify	O
a	O
CommandValidationHandler	O
ScriptBlock	O
which	O
runs	O
before	O
submitting	O
the	O
command	B-Operating_System
.	O
</s>
<s>
This	O
allows	O
for	O
custom	O
correcting	O
of	O
commonly	O
mistyped	O
commands	O
,	O
and	O
verification	O
before	O
actually	O
running	O
the	O
command	B-Operating_System
.	O
</s>
<s>
Unix/Linux	O
systems	O
may	O
offer	O
other	O
tools	O
support	O
using	O
progress	O
indicators	O
from	O
scripts	O
or	O
as	O
standalone-commands	O
,	O
such	O
as	O
the	O
program	O
"	O
pv	O
"	O
.	O
</s>
<s>
PowerShell	B-Application
has	O
a	O
built-in	O
command	B-Operating_System
and	O
API	O
functions	O
(	O
to	O
be	O
used	O
when	O
authoring	O
commands	O
)	O
for	O
writing/updating	O
a	O
progress	O
bar	O
.	O
</s>
<s>
JP	B-Application
Software	I-Application
command-line	B-Application
processors	O
provide	O
user-configurable	O
colorization	O
of	O
file	O
and	O
directory	O
names	O
in	O
directory	O
listings	O
based	O
on	O
their	O
file	O
extension	O
and/or	O
attributes	O
through	O
an	O
optionally	O
defined	O
%COLORDIR%	O
environment	O
variable	O
.	O
</s>
<s>
For	O
the	O
Unix/Linux	O
shells	O
,	O
this	O
is	O
a	O
feature	O
of	O
the	O
command	B-Operating_System
and	O
the	O
terminal	O
.	O
</s>
<s>
The	O
command	B-Application
line	I-Application
processors	O
in	O
DOS	B-Operating_System
Plus	I-Operating_System
,	O
Multiuser	B-Operating_System
DOS	I-Operating_System
,	O
REAL/32	B-Operating_System
and	O
in	O
all	O
versions	O
of	O
DR-DOS	B-Application
support	O
a	O
number	O
of	O
optional	O
environment	O
variables	O
to	O
define	O
escape	O
sequences	O
allowing	O
to	O
control	O
text	O
highlighting	O
,	O
reversion	O
or	O
colorization	O
for	O
display	O
or	O
print	O
purposes	O
in	O
commands	O
like	O
TYPE	B-Device
.	O
</s>
<s>
All	O
mentioned	O
command	B-Application
line	I-Application
processors	O
support	O
%$ON%	O
and	O
%$OFF%	O
.	O
</s>
<s>
A	O
typical	O
sequence	O
for	O
%$ON%	O
would	O
be	O
\033[ 1m	O
in	O
conjunction	O
with	O
ANSI.SYS	O
,	O
\033p	O
for	O
an	O
ASCII	B-Protocol
terminal	O
or	O
\016	O
for	O
an	O
IBM	O
or	O
ESC/P	B-Language
printer	O
.	O
</s>
<s>
The	O
variables	O
%$HEADER%	O
and	O
%$FOOTER%	O
are	O
only	O
supported	O
by	O
COMMAND.COM	B-Operating_System
in	O
DR-DOS	B-Application
7.02	O
and	O
higher	O
to	O
define	O
sequences	O
emitted	O
before	O
and	O
after	O
text	O
blocks	O
in	O
order	O
to	O
control	O
text	O
highlighting	O
,	O
pagination	O
or	O
other	O
formatting	O
options	O
.	O
</s>
<s>
For	O
the	O
Unix/Linux	O
shells	O
,	O
this	O
is	O
a	O
feature	O
of	O
the	O
terminal	O
.	O
</s>
<s>
A	O
defining	O
feature	O
of	O
the	O
fish	B-Language
shell	I-Language
is	O
built-in	O
syntax	O
highlighting	O
,	O
As	O
the	O
user	O
types	O
,	O
text	O
is	O
colored	O
to	O
represent	O
whether	O
the	O
input	O
is	O
a	O
valid	O
command	B-Operating_System
or	O
not	O
(	O
the	O
executable	O
exists	O
and	O
the	O
user	O
has	O
permissions	O
to	O
run	O
it	O
)	O
,	O
and	O
valid	O
file	O
paths	O
are	O
underlined	O
.	O
</s>
<s>
An	O
independent	O
project	O
offers	O
syntax	O
highlighting	O
as	O
an	O
add-on	O
to	O
the	O
Z	B-Application
Shell	I-Application
(	O
zsh	B-Application
)	O
.	O
</s>
<s>
PowerShell	B-Application
provides	O
customizable	O
syntax	O
highlighting	O
on	O
the	O
command	B-Application
line	I-Application
through	O
the	O
PSReadLine	O
module	O
.	O
</s>
<s>
This	O
module	O
can	O
be	O
used	O
with	O
PowerShell	B-Application
v3.0	O
+	O
,	O
and	O
it	O
's	O
included	O
with	O
v5.0	O
.	O
</s>
<s>
Additionally	O
,	O
it	O
is	O
loaded	O
by	O
default	O
in	O
the	O
command	B-Application
line	I-Application
host	O
"	O
powershell.exe	B-Application
"	O
in	O
v5.0	O
.	O
</s>
<s>
The	O
PowerShell	B-Application
ISE	O
also	O
includes	O
syntax	O
highlighting	O
on	O
the	O
command	B-Application
line	I-Application
as	O
well	O
as	O
in	O
the	O
script	O
pane	O
.	O
</s>
<s>
Take	B-Application
Command	I-Application
Console	I-Application
(	O
TCC	B-Application
)	O
offers	O
syntax	O
highlighting	O
in	O
the	O
integrated	O
environment	O
.	O
</s>
<s>
4DOS	B-Application
,	O
4OS2	B-Application
,	O
4NT	B-Application
/	O
Take	B-Application
Command	I-Application
Console	I-Application
and	O
PowerShell	B-Application
(	O
in	O
PowerShell	B-Application
ISE	O
)	O
looks	O
up	O
context-sensitive	O
help	O
information	O
when	O
is	O
pressed	O
.	O
</s>
<s>
Zsh	B-Application
provides	O
various	O
forms	O
of	O
configurable	O
context-sensitive	O
help	O
as	O
part	O
of	O
its	O
widget	O
,	O
command	B-Operating_System
,	O
or	O
in	O
the	O
completion	O
of	O
options	O
for	O
some	O
commands	O
.	O
</s>
<s>
The	O
fish	B-Language
shell	I-Language
provides	O
brief	O
descriptions	O
of	O
a	O
command	B-Operating_System
's	O
flags	O
during	O
tab	O
completion	O
.	O
</s>
<s>
A	O
command	B-Operating_System
builder	O
is	O
a	O
guided	O
dialog	O
which	O
assists	O
the	O
user	O
in	O
filling	O
in	O
a	O
command	B-Operating_System
.	O
</s>
<s>
PowerShell	B-Application
has	O
a	O
command	B-Operating_System
builder	O
which	O
is	O
available	O
in	O
PowerShell	B-Application
ISE	O
or	O
which	O
can	O
be	O
displayed	O
separately	O
through	O
the	O
cmdlet	O
.	O
</s>
<s>
?	O
ksh	B-Language
(	O
ksh93t+	O
)	O
pdkshzshash	O
(	O
via	O
)	O
CCP	O
??	O
</s>
<s>
?	O
COMMAND.COM	B-Operating_System
(	O
only	O
Auto-fail	O
(	O
via	O
(	O
or	O
in	O
some	O
versions	O
of	O
DR-DOS	B-Application
)	O
)	O
OS/2	B-Application
CMD.EXE	B-Device
?	O
</s>
<s>
?	O
Windows	B-Application
CMD.EXE4DOS	O
??	O
4OS2	B-Application
????????	O
</s>
<s>
(	O
function	O
)	O
?	O
TCC	B-Application
(	O
formerly	O
4NT	B-Application
)	O
???	O
</s>
<s>
(	O
function	O
)	O
(	O
via	O
command	B-Operating_System
)	O
PowerShell	B-Application
(	O
Try-Catch-Finally	O
)	O
The	O
.NET	B-Application
System.Math	O
class	O
defines	O
mathematical	O
functions	O
that	O
can	O
be	O
used	O
through	O
the	O
shortcut	O
,	O
e.g.	O
</s>
<s>
for	O
the	O
sinus	O
function.rc	O
???	O
BeanShell	B-Language
??	O
</s>
<s>
ShellString	O
processingAlternation	O
(	O
Brace	O
expansion	O
)	O
Pattern	O
matching	O
(	O
regular	B-Language
expressions	I-Language
built-in	O
)	O
Pattern	O
matching	O
(	O
filename	O
globbing	B-Language
)	O
Globbing	B-Language
qualifiers	O
(	O
filename	O
generation	O
based	O
on	O
file	O
attributes	O
)	O
Recursive	O
globbing	B-Language
(	O
generating	O
files	O
from	O
any	O
level	O
of	O
subdirectories	O
)	O
Bourne	B-Device
shell	I-Device
1977	O
version	O
?	O
Bourne	B-Device
shell	I-Device
recent	O
version	O
(	O
prefix	O
and	O
suffix	O
stripping	O
in	O
variable	O
expansion	O
)	O
POSIX	O
shell	O
(	O
prefix	O
and	O
suffix	O
stripping	O
in	O
variable	O
expansion	O
)	O
bash	B-Operating_System
(	O
v4.0	O
)	O
(	O
prefix	O
and	O
suffix	O
stripping	O
in	O
variable	O
expansion	O
)	O
(	O
)	O
cshtcshHamilton	O
C	O
shellScsh	O
?	O
</s>
<s>
?	O
ksh	B-Language
(	O
ksh93t+	O
)	O
(	O
prefix	O
,	O
suffix	O
stripping	O
and	O
string	O
replacement	O
in	O
variable	O
expansion	O
)	O
(	O
with	O
,	O
no	O
following	O
of	O
symlinks	O
)	O
pdksh	O
?	O
zsh	B-Application
(	O
through	O
variable	O
processing	O
:	O
e.g.	O
</s>
<s>
substring	O
extraction	O
,	O
various	O
transformations	O
via	O
parameter	O
expansion	O
)	O
(	O
or	O
to	O
follow	O
symlinks	O
)	O
ash	B-Operating_System
?	O
</s>
<s>
?	O
CCPCOMMAND.COMOS/2	O
CMD.EXE	B-Device
(	O
only	O
in	O
command	B-Operating_System
)	O
Windows	B-Application
CMD.EXE	B-Device
(	O
only	O
through	O
and	O
)	O
(	O
only	O
in	O
command	B-Operating_System
)	O
(	O
via	O
command	B-Operating_System
,	O
or	O
,	O
where	O
available	O
,	O
indirectly	O
via	O
subdir	O
option	O
)	O
4DOS	B-Application
(	O
through	O
variable	O
functions	O
,	O
extended	O
environment	O
variable	O
processing	O
,	O
various	O
string	O
commands	O
and	O
and	O
)	O
(	O
via	O
attribute	O
and	O
description	O
options	O
and	O
size	O
,	O
time	O
,	O
date	O
,	O
and	O
file	O
exclusion	O
ranges	O
)	O
(	O
via	O
command	B-Operating_System
,	O
or	O
indirectly	O
via	O
command	B-Operating_System
or	O
,	O
where	O
available	O
,	O
subdir	O
option	O
)	O
4OS2	B-Application
???	O
</s>
<s>
?	O
TCC	B-Application
(	O
formerly	O
4NT	B-Application
)	O
(	O
through	O
variable	O
functions	O
,	O
extended	O
environment	O
variable	O
processing	O
,	O
various	O
string	O
commands	O
and	O
and	O
)	O
(	O
via	O
attribute	O
and	O
description	O
options	O
and	O
size	O
,	O
time	O
,	O
date	O
,	O
owner	O
,	O
and	O
file	O
exclusion	O
ranges	O
)	O
(	O
via	O
command	B-Operating_System
,	O
or	O
indirectly	O
via	O
command	B-Operating_System
or	O
,	O
where	O
available	O
,	O
subdir	O
option	O
)	O
PowerShell	B-Application
??	O
rc	B-Operating_System
??	O
BeanShell	B-Language
????	O
</s>
<s>
ShellPipesCommand	O
substitutionProcess	O
substitutionSubshellsTCP/UDP	O
connections	O
as	O
streamsKeystroke	O
stackingBourne	O
shellxautomation	O
and	O
xdotool	O
can	O
be	O
used	O
to	O
generate	O
keystrokes	O
under	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
;	O
or	O
a	O
program	O
can	O
be	O
run	O
in	O
a	O
pseudoterminal	B-Protocol
to	O
be	O
able	O
to	O
control	O
it	O
(	O
as	O
with	O
the	O
tool	O
)	O
.POSIX	O
shellbash	O
(	O
v4.0	O
)	O
cshtcshHamilton	O
C	B-Operating_System
shell	I-Operating_System
?	O
Scsh	B-Language
??	O
</s>
<s>
?	O
ksh	B-Language
(	O
ksh93t+	O
)	O
pdkshzshashCCPCOMMAND.COM	O
(	O
only	O
under	O
DR-DOS	B-Application
multitasker	O
via	O
)	O
OS/2	B-Application
CMD.EXE	B-Device
?	O
Windows	B-Application
CMD.EXE4DOS	O
?	O
</s>
<s>
(	O
via	O
and	O
,	O
or	O
via	O
,	O
and	O
and	O
)	O
(	O
via	O
and	O
)	O
4OS2	B-Application
???	O
</s>
<s>
(	O
via	O
)	O
TCC	B-Application
(	O
formerly	O
4NT	B-Application
)	O
?	O
</s>
<s>
(	O
via	O
and	O
)	O
(	O
via	O
,	O
,	O
,	O
,	O
,	O
and	O
,	O
client	O
only	O
)	O
(	O
via	O
)	O
PowerShell	B-Application
?	O
rc	B-Operating_System
?	O
BeanShell	B-Language
???	O
</s>
<s>
By	O
sending	O
keystroke	O
sequences	O
the	O
user	O
may	O
be	O
able	O
to	O
direct	O
the	O
application	O
to	O
perform	O
actions	O
that	O
would	O
be	O
impossible	O
to	O
achieve	O
through	O
input	O
redirection	B-Device
or	O
would	O
otherwise	O
require	O
an	O
interactive	O
user	O
.	O
</s>
<s>
It	O
also	O
allows	O
to	O
simulate	O
keys	O
which	O
are	O
not	O
present	O
on	O
a	O
keyboard	O
(	O
because	O
the	O
corresponding	O
keys	O
do	O
not	O
physically	O
exist	O
or	O
because	O
a	O
different	O
keyboard	O
layout	O
is	O
being	O
used	O
)	O
and	O
therefore	O
would	O
be	O
impossible	O
to	O
type	B-Device
by	O
a	O
user	O
.	O
</s>
<s>
?	O
The	O
execute	O
permission	O
is	O
enforced	O
by	O
a	O
separate	O
program	O
,	O
the	O
program	B-Operating_System
loader	I-Operating_System
,	O
by	O
refusing	O
to	O
invoke	O
the	O
interpreter	O
(	O
possibly	O
a	O
shell	O
)	O
specified	O
by	O
the	O
script	O
's	O
hashbang	B-Operating_System
.	O
</s>
<s>
The	O
interpreter	O
does	O
not	O
enforce	O
the	O
execute	O
permission	O
if	O
invoked	O
directly	O
as	O
the	O
program	B-Operating_System
loader	I-Operating_System
would	O
,	O
with	O
the	O
file	O
as	O
an	O
argument	O
;	O
this	O
only	O
requires	O
read	O
permission	O
,	O
as	O
does	O
piping	O
the	O
file	O
as	O
input	O
to	O
the	O
interpreter	O
,	O
in	O
which	O
case	O
the	O
interpreter	O
cannot	O
see	O
the	O
execute	O
permission.POSIX	O
shell	O
?	O
bash	B-Operating_System
(	O
v4.0	O
)	O
?	O
csh	B-Operating_System
?	O
tcsh	B-Language
?	O
Hamilton	O
C	O
shellScsh	O
?	O
ksh	B-Language
(	O
ksh93t+	O
)	O
?	O
pdksh	O
?	O
zsh	B-Application
?	O
ash	B-Operating_System
?	O
CCPCOMMAND.COM	O
(	O
only	O
under	O
DR-DOS	B-Application
,	O
prompts	O
for	O
password	O
if	O
file/directory	O
is	O
protected	O
)	O
(	O
only	O
under	O
DR-DOS	B-Application
via	O
syntax	O
)	O
Under	O
DR-DOS	B-Application
the	O
password	O
separator	O
for	O
file	O
and	O
directory	O
passwords	O
is	O
a	O
semicolon	O
.	O
</s>
<s>
This	O
is	O
also	O
supported	O
under	O
4DOS	B-Application
for	O
as	O
long	O
as	O
the	O
command	B-Operating_System
does	O
not	O
support	O
include	O
lists	O
.	O
</s>
<s>
Under	O
4DOS	B-Application
,	O
the	O
password	O
separator	O
must	O
be	O
doubled	O
for	O
all	O
commands	O
supporting	O
include	O
lists	O
in	O
order	O
to	O
distinguish	O
passwords	O
from	O
include	O
lists	O
.	O
</s>
<s>
DR-DOS	B-Application
7.02	O
and	O
higher	O
optionally	O
accept	O
a	O
doubled	O
semicolon	O
as	O
well	O
,	O
so	O
that	O
doubled	O
semicolons	O
work	O
under	O
both	O
COMMAND.COM	B-Operating_System
and	O
4DOS	B-Application
regardless	O
of	O
the	O
command	B-Operating_System
executed	O
.	O
</s>
<s>
(	O
only	O
under	O
DR-DOS	B-Application
,	O
if	O
files	O
are	O
password-protected	O
for	O
read	O
and/or	O
execute	O
permission	O
)	O
DR-DOS	B-Application
supports	O
file	O
passwords	O
for	O
read/write/delete	O
and	O
optionally	O
execute	O
permissions	O
.	O
</s>
<s>
batch	O
scripts	O
require	O
a	O
password	O
to	O
read.OS/2	O
CMD.EXEWindows	O
CMD.EXE4DOS	O
(	O
via	O
or	O
)	O
and	O
echoes	O
back	O
asterisks	O
for	O
each	O
typed	O
character	O
.	O
</s>
<s>
(	O
only	O
under	O
DR-DOS	B-Application
via	O
syntax	O
)	O
(	O
only	O
under	O
DR-DOS	B-Application
,	O
if	O
files	O
are	O
password-protected	O
for	O
read	O
and/or	O
execute	O
permission	O
)	O
4OS2	B-Application
?	O
TCC	B-Application
(	O
formerly	O
4NT	B-Application
)	O
(	O
via	O
,	O
or	O
)	O
PowerShell	B-Application
reads	O
a	O
string	O
of	O
characters	O
from	O
the	O
input	O
device	O
into	O
an	O
encrypted	O
string	O
,	O
one	O
character	O
at	O
a	O
time	O
thus	O
ensuring	O
that	O
there	O
is	O
no	O
memory	O
image	O
of	O
the	O
clear	O
text	O
which	O
could	O
be	O
gleaned	O
from	O
scanning	O
memory	O
,	O
or	O
from	O
crash	O
dumps	O
,	O
memory	O
dumps	O
,	O
paging	O
files	O
,	O
log	O
files	O
or	O
similar.PowerShell	O
script	O
files	O
(	O
files	O
)	O
are	O
by	O
default	O
associated	O
with	O
the	O
Notepad	O
editor	O
,	O
not	O
with	O
the	O
PowerShell	B-Application
execution	O
engine	O
.	O
</s>
<s>
Invoking	O
a	O
file	O
will	O
launch	O
Notepad	O
rather	O
than	O
executing	O
the	O
script.Startup	O
scripts	O
per	O
computer/user	O
can	O
import	O
modules	O
and	O
expose	O
a	O
subset	O
the	O
commands/functions	O
available	O
in	O
the	O
modules.rc	O
?	O
BeanShell	B-Language
??????	O
</s>
<s>
?	O
VMS	B-Operating_System
DCLfish	O
?	O
</s>
<s>
The	O
shells	O
bash	B-Operating_System
,	O
zsh	B-Application
and	O
PowerShell	B-Application
offer	O
this	O
as	O
a	O
specific	O
feature	O
.	O
</s>
<s>
Shells	O
executing	O
on	O
a	O
Unix/Linux	O
operating	O
system	O
can	O
use	O
the	O
external	O
command	B-Operating_System
to	O
switch	O
off/on	O
echoing	O
of	O
input	O
characters	O
.	O
</s>
<s>
In	O
addition	O
to	O
not	O
echoing	O
back	O
the	O
characters	O
,	O
PowerShell	B-Application
's	O
option	O
also	O
encrypts	O
the	O
input	O
character-by-character	O
during	O
the	O
input	O
process	O
,	O
ensuring	O
that	O
the	O
string	O
is	O
never	O
represented	O
unencrypted	O
in	O
memory	O
where	O
it	O
could	O
be	O
compromised	O
through	O
memory	O
dumps	O
,	O
scanning	O
,	O
transcription	O
etc	O
.	O
</s>
<s>
PowerShell	B-Application
can	O
work	O
with	O
encrypted	O
string	O
variables/parameters	O
.	O
</s>
<s>
PowerShell	B-Application
also	O
supports	O
saving	O
of	O
such	O
encrypted	O
strings	O
in	O
text	O
files	O
,	O
protected	O
by	O
a	O
key	O
owned	O
by	O
the	O
current	O
user	O
.	O
</s>
<s>
Some	O
operating	B-General_Concept
systems	I-General_Concept
define	O
an	O
execute	O
permission	O
which	O
can	O
be	O
granted	O
to	O
users/groups	O
for	O
a	O
file	O
.	O
</s>
<s>
On	O
Unix	B-Application
systems	I-Application
,	O
the	O
execute	O
permission	O
controls	O
access	O
to	O
invoking	O
the	O
file	O
as	O
a	O
program	O
,	O
and	O
applies	O
both	O
to	O
executables	O
and	O
scripts	O
.	O
</s>
<s>
As	O
the	O
permission	O
is	O
enforced	O
in	O
the	O
program	B-Operating_System
loader	I-Operating_System
,	O
no	O
obligation	O
is	O
needed	O
from	O
the	O
invoking	O
program	O
,	O
nor	O
the	O
invoked	O
program	O
,	O
in	O
enforcing	O
the	O
execute	O
permission	O
this	O
also	O
goes	O
for	O
shells	O
and	O
other	O
interpreter	O
programs	O
.	O
</s>
<s>
The	O
behaviour	O
is	O
mandated	O
by	O
the	O
POSIX	B-Language
C	I-Language
library	I-Language
that	O
is	O
used	O
for	O
interfacing	O
with	O
the	O
kernel	O
.	O
</s>
<s>
Although	O
Windows	B-Application
also	O
specifies	O
an	O
execute	O
permission	O
,	O
none	O
of	O
the	O
Windows-specific	O
shells	O
block	O
script	O
execution	O
if	O
the	O
permission	O
has	O
not	O
been	O
granted	O
.	O
</s>
<s>
PowerShell	B-Application
can	O
be	O
set	O
to	O
block	O
execution	O
of	O
scripts	O
which	O
has	O
been	O
marked	O
as	O
obtained	O
from	O
an	O
unknown/untrusted	O
origin	O
(	O
e.g.	O
</s>
<s>
mark	O
files	O
downloaded	O
from	O
the	O
internet	O
with	O
the	O
origin	O
zone	O
in	O
an	O
alternate	O
data	O
stream	B-Operating_System
which	O
is	O
understood	O
by	O
PowerShell	B-Application
.	O
</s>
<s>
PowerShell	B-Application
can	O
be	O
set	O
to	O
allow	O
execution	O
of	O
otherwise	O
blocked	O
scripts	O
(	O
e.g.	O
</s>
<s>
PowerShell	B-Application
allows	O
script	O
blocking	O
policies	O
to	O
be	O
enforced	O
at	O
multiple	O
levels	O
:	O
Local	O
machine	O
,	O
current	O
user	O
etc	O
.	O
</s>
<s>
While	O
not	O
a	O
security	O
boundary	O
(	O
the	O
command	B-Operating_System
accessing	O
a	O
resource	O
is	O
blocked	O
rather	O
than	O
the	O
resource	O
)	O
this	O
is	O
nevertheless	O
typically	O
used	O
to	O
restrict	O
users	O
 '	O
actions	O
before	O
logging	O
in	O
.	O
</s>
<s>
A	O
restricted	O
mode	O
is	O
part	O
of	O
the	O
POSIX	O
specification	O
for	O
shells	O
,	O
and	O
most	O
of	O
the	O
Linux/Unix	O
shells	O
support	O
such	O
a	O
mode	O
where	O
several	O
of	O
the	O
built-in	O
commands	O
are	O
disabled	O
and	O
only	O
external	O
commands	O
from	O
a	O
certain	O
directory	O
can	O
be	O
invoked	O
.	O
</s>
<s>
PowerShell	B-Application
supports	O
restricted	O
modes	O
through	O
session	O
configuration	O
files	O
or	O
session	O
configurations	O
.	O
</s>
<s>
PowerShell	B-Application
can	O
contain	O
constants	O
and	O
expressions	O
using	O
a	O
restricted	O
subset	O
of	O
operators	O
and	O
commands	O
.	O
</s>
<s>
PowerShell	B-Application
data	O
sections	O
are	O
used	O
when	O
e.g.	O
</s>
