Change PS1 when running as administrator

Change PS1 when running as administrator

[GrahamC]

On Monday, 16 June 2014, 12:25, Frank Fesevur <ffes@users.sourceforge.net> wrote:

> Hi,
> 
> I recently bought a new home computer, so I switched from XP to Win81.
> With Win81 every now and then I need to start cygwin as administrator
> (right click shortcut or tile, run as administrator) to do things that
> I can't do as a normal user.
>
> When I run as administrator I change my PS1 from "$" to "#" with these
> line in ~/.bashrc.
>
> if id -Gn | grep -i Administrators > /dev/null
> then
>    PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n# '
> else
>    PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n\$ '
> fi
>
> I don't know if the test can be done a better/easier way, but it works
> for me on a Dutch Win81. I tested it with both 1.7.30 and a recent
> AD/SAM snapshot.
>
> If more people like this idea, maybe it could included in /etc/bash.bashrc?
>
> Regards,
> Frank

Personally I use a test like:  if [ -w /etc ] for this, which works provided a write ACL has not been added for ordinary users on the directory \cygwin\etc. Administrators have write access to this directory.

Bash supports regular expressions, so if [[ `id` =~ Administrators ]] is a shorter test equivalent to your example.

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Re: Change PS1 when running as administrator

[Chris J. Breisch]

GrahamC wrote:
> On Monday, 16 June 2014, 12:25, Frank Fesevur<ffes@users.sourceforge.net>  wrote:
>
>> Hi,
>>
>> I recently bought a new home computer, so I switched from XP to Win81.
>> With Win81 every now and then I need to start cygwin as administrator
>> (right click shortcut or tile, run as administrator) to do things that
>> I can't do as a normal user.
>>
>> When I run as administrator I change my PS1 from "$" to "#" with these
>> line in ~/.bashrc.
>>
>> if id -Gn | grep -i Administrators>  /dev/null
>> then
>>      PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n# '
>> else
>>      PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n\$ '
>> fi
>>
>> I don't know if the test can be done a better/easier way, but it works
>> for me on a Dutch Win81. I tested it with both 1.7.30 and a recent
>> AD/SAM snapshot.
>>
>> If more people like this idea, maybe it could included in /etc/bash.bashrc?
>>
>> Regards,
>> Frank
>
> Personally I use a test like:  if [ -w /etc ] for this, which works provided a write ACL has not been added for ordinary users on the directory \cygwin\etc. Administrators have write access to this directory.
>
> Bash supports regular expressions, so if [[ `id` =~ Administrators ]] is a shorter test equivalent to your example.

You might want to look at this thread: 
https://sourceware.org/ml/cygwin/2014-04/msg00256.html

I use the registry test, but the id method would also work.


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Re: Change PS1 when running as administrator

[Frank Fesevur]

2014-06-16 21:00 GMT+02:00 Chris J. Breisch:
> You might want to look at this thread:
> https://sourceware.org/ml/cygwin/2014-04/msg00256.html

Thanks for showing this threads. Missed it back then.

> I use the registry test, but the id method would also work.

I think the id command is a better way since it tells you that the
user is member of the administrator group. That really tells you what
you need to know. But the registry trick will work almost always, I
sure :-)

Regards,
Frank

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Re: Change PS1 when running as administrator

[Eric Blake]

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On 06/17/2014 11:19 AM, Ernie Rael wrote:
> On 6/17/2014 9:34 AM, Andrey Repin wrote:
> 
>>>       [[ $(id -G) =~ \b544\b ]]
>>> was suggested (the suggestion used symbolic name instead of a number and
>>> didn't use word boundary). Seems like word boundary is needed, but I
>>> couldn't get this to work. Are the regex boundary matchers not
>>> supported  by bash =~ operator?
>> I don't think bash equivalent of test implements Perl RE.
>> Neither the base test implementation, to that extent.
> 
> I thought, perhaps incorrectly, that \b has been around forever and is
> posix.

Forever in Linux, but not required by POSIX and not present in BSD (from
which Cygwin inherits its regex implementation).

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Re: Change PS1 when running as administrator

[Eric Blake]

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On 06/17/2014 10:21 AM, Ernie Rael wrote:
> On 6/17/2014 1:45 AM, GrahamC wrote:
>> If we are looking for other alternatives the GROUPS environment
>> variable can also be used:
>>
>> PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n\$ '
>> for G in "${GROUPS[@]}"; do
>>      if [ "$G" = 544 ]; then
>>          PS1='\[\e]0;Administrator \w\a\]\n\[\e[32m\]\u@\h
>> \[\e[33m\]\w\[\e[0m\]\n# '
>>      fi
>> done
> 
> Speaking of alternatives,
> 
> For matching in bash, something like
> 
>     [[ $(id -G) =~ \b544\b ]]

\b is a glibc regex() extension, not supported in Cygwin regex

Cygwin supports \< as a shortcut for [[:<:]], and \> as a shortcut for
[[:>:]], which are both BSD extensions.  \b is roughly equivalent to
[[:<:][:>:]] - but someone would have to actually patch cygwin's
regcomp.c to enable that extension.

https://cygwin.com/viewvc/src/winsup/cygwin/regex/regcomp.c?view=co&revision=1.16&content-type=text%2Fplain

> 
> was suggested (the suggestion used symbolic name instead of a number and
> didn't use word boundary). Seems like word boundary is needed, but I
> couldn't get this to work. Are the regex boundary matchers not
> supported  by bash =~ operator?

bash only supports what the libc regex() supports, and since Cygwin
regex() is not as full-featured as glibc regex(), the answer is that you
can't use \b in Cygwin bash (yet; PTC).

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Re: Change PS1 when running as administrator

[Ernie Rael]

On 6/17/2014 9:34 AM, Andrey Repin wrote:

>>       [[ $(id -G) =~ \b544\b ]]
>> was suggested (the suggestion used symbolic name instead of a number and
>> didn't use word boundary). Seems like word boundary is needed, but I
>> couldn't get this to work. Are the regex boundary matchers not
>> supported  by bash =~ operator?
> I don't think bash equivalent of test implements Perl RE.
> Neither the base test implementation, to that extent.

I thought, perhaps incorrectly, that \b has been around forever and is 
posix.

In any event, looks like

     [[ $(id -G) =~ (^| )544($| ) ]]

would work.

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Re: Change PS1 when running as administrator

[Andrey Repin]

Greetings, Ernie Rael!

> On 6/17/2014 1:45 AM, GrahamC wrote:
>> If we are looking for other alternatives the GROUPS environment variable can also be used:
>>
>> PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n\$ '
>> for G in "${GROUPS[@]}"; do
>>      if [ "$G" = 544 ]; then
>>          PS1='\[\e]0;Administrator \w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n# '
>>      fi
>> done

> Speaking of alternatives,

> For matching in bash, something like

>      [[ $(id -G) =~ \b544\b ]]

> was suggested (the suggestion used symbolic name instead of a number and
> didn't use word boundary). Seems like word boundary is needed, but I
> couldn't get this to work. Are the regex boundary matchers not
> supported  by bash =~ operator?

I don't think bash equivalent of test implements Perl RE.
Neither the base test implementation, to that extent.

> Can use something like

>      id -G | grep -q "\b544\b"

> (or echo ${GROUPS[@]} | ...)


--
WBR,
Andrey Repin (anrdaemon@yandex.ru) 17.06.2014, <20:30>

Sorry for my terrible english...


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Re: Change PS1 when running as administrator

[Ernie Rael]

On 6/17/2014 1:45 AM, GrahamC wrote:
> If we are looking for other alternatives the GROUPS environment variable can also be used:
>
> PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n\$ '
> for G in "${GROUPS[@]}"; do
>      if [ "$G" = 544 ]; then
>          PS1='\[\e]0;Administrator \w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n# '
>      fi
> done

Speaking of alternatives,

For matching in bash, something like

     [[ $(id -G) =~ \b544\b ]]

was suggested (the suggestion used symbolic name instead of a number and
didn't use word boundary). Seems like word boundary is needed, but I
couldn't get this to work. Are the regex boundary matchers not
supported  by bash =~ operator?  Can use something like

     id -G | grep -q "\b544\b"

(or echo ${GROUPS[@]} | ...)

  -ernie



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Re: Change PS1 when running as administrator

[GrahamC]

> Frank Fesevur writes:
>> When I run as administrator I change my PS1 from "$" to "#" with these
>> line in ~/.bashrc.
>>
>> if id -Gn | grep -i Administrators > /dev/null
>
> If anything I'd check for membership in group 544.  "Administrators"
> surely is one of these strings that gets localized depending on the
> phase of the moon or something.  I can't look right now, but I'm pretty
> sure it says "Administratoren" in a german Windows version.

> On all my Dutch Windows all group names are localized apart from
> 544/Administrators.

># id
>uid=1000(Frank) gid=513(Geen)
>groups=513(Geen),0(root),544(Administrators),545(Gebruikers)

>But I agree checking the numeric value is better.

>> If more people like this idea, maybe it could included in /etc/bash.bashrc?
>
> I'll have to think about it, but I lean toward putting it into profile.d
> instead.

>Thanks for considering.
>The other PS1 setting (user@host dir) is also in bash.bashrc. That's
>why I suggested bash.bashrc.

>Regards,
>Frank

If we are looking for other alternatives the GROUPS environment variable can also be used:

PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n\$ '
for G in "${GROUPS[@]}"; do
    if [ "$G" = 544 ]; then
        PS1='\[\e]0;Administrator \w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n# '
    fi
done

Somebody really clever with regular expressions could probably make an equivalent one line test.

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Re: Change PS1 when running as administrator

[Achim Gratz]

Thomas Wolff <towo <at> towo.net> writes:
> As Corinna had said. Yet, I'd like to check official documentation to 
> confirm "544" is a constant for this purpose.

I suggest you go to MSDN and search for "well-known security identifiers"
and then read Corinnas explanation of how these are mapped to Cygwin UID/GID
again.


Regards,
Achim.


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Re: Change PS1 when running as administrator

[Thomas Wolff]

Am 16.06.2014 22:04, schrieb Frank Fesevur:
> 2014-06-16 21:06 GMT+02:00 Achim Gratz:
>> Frank Fesevur writes:
>>> When I run as administrator I change my PS1 from "$" to "#" with these
>>> line in ~/.bashrc.
>>>
>>> if id -Gn | grep -i Administrators > /dev/null
>> If anything I'd check for membership in group 544.  "Administrators"
>> surely is one of these strings that gets localized depending on the
>> phase of the moon or something.  I can't look right now, but I'm pretty
>> sure it says "Administratoren" in a german Windows version.
> On all my Dutch Windows all group names are localized apart from
> 544/Administrators.
I can confirm it is localized in German Windows (as I had been told 
myself when I proposed the same idea here 2 months ago:) ).
> # id
> uid=1000(Frank) gid=513(Geen)
> groups=513(Geen),0(root),544(Administrators),545(Gebruikers)
>
> But I agree checking the numeric value is better.
As Corinna had said. Yet, I'd like to check official documentation to 
confirm "544" is a constant for this purpose.
Other suggestions had been discussed (like checking something in 
/proc/something...).
Thomas

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Re: Change PS1 when running as administrator

[Frank Fesevur]

2014-06-16 21:06 GMT+02:00 Achim Gratz:
> Frank Fesevur writes:
>> When I run as administrator I change my PS1 from "$" to "#" with these
>> line in ~/.bashrc.
>>
>> if id -Gn | grep -i Administrators > /dev/null
>
> If anything I'd check for membership in group 544.  "Administrators"
> surely is one of these strings that gets localized depending on the
> phase of the moon or something.  I can't look right now, but I'm pretty
> sure it says "Administratoren" in a german Windows version.

On all my Dutch Windows all group names are localized apart from
544/Administrators.

# id
uid=1000(Frank) gid=513(Geen)
groups=513(Geen),0(root),544(Administrators),545(Gebruikers)

But I agree checking the numeric value is better.

>> If more people like this idea, maybe it could included in /etc/bash.bashrc?
>
> I'll have to think about it, but I lean toward putting it into profile.d
> instead.

Thanks for considering.
The other PS1 setting (user@host dir) is also in bash.bashrc. That's
why I suggested bash.bashrc.

Regards,
Frank

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Re: Change PS1 when running as administrator

[Achim Gratz]

Frank Fesevur writes:
> When I run as administrator I change my PS1 from "$" to "#" with these
> line in ~/.bashrc.
>
> if id -Gn | grep -i Administrators > /dev/null

If anything I'd check for membership in group 544.  "Administrators"
surely is one of these strings that gets localized depending on the
phase of the moon or something.  I can't look right now, but I'm pretty
sure it says "Administratoren" in a german Windows version.

> If more people like this idea, maybe it could included in /etc/bash.bashrc?

I'll have to think about it, but I lean toward putting it into profile.d
instead.


Regards,
Achim.
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Change PS1 when running as administrator

[Frank Fesevur]

Hi,

I recently bought a new home computer, so I switched from XP to Win81.
With Win81 every now and then I need to start cygwin as administrator
(right click shortcut or tile, run as administrator) to do things that
I can't do as a normal user.

When I run as administrator I change my PS1 from "$" to "#" with these
line in ~/.bashrc.

if id -Gn | grep -i Administrators > /dev/null
then
    PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n# '
else
    PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]\n\$ '
fi

I don't know if the test can be done a better/easier way, but it works
for me on a Dutch Win81. I tested it with both 1.7.30 and a recent
AD/SAM snapshot.

If more people like this idea, maybe it could included in /etc/bash.bashrc?

Regards,
Frank

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