GNU emacs locks files modified with CVS

GNU emacs locks files modified with CVS

[Pepijn Kenter]

Hi all.

I've got a problem when I use su to log in as another user and try to 
edit a file that is modified in CVS. Let me show you the sequence of 
commands that leads to the problem.

When loged in as user1 type:
su user2
emacs file.pro # edit, exit and save the changes
emacs file.pro # file.pro is now read only.

I can not edit file.pro the second time because it is apperently locked 
by user2 (as shown in the status line? of emacs). File permissions are 
correct and the onwner of file.pro (still) is user2.

After some googling I think the possible cause is that emacs is 
inconsistent in the way it handles the USER and LOGNAME variables.
Indeed USER is set to user2 whereas LOGNAME is still user1. When I 
change LOGNAME to user2 the problem disappears.

So, what to do?
I've found a very old message (1994) with a patch to solve this problem
http://groups.google.nl/groups?q=LOGNAME+USER+emacs&hl=nl&lr=lang_de|lang_en|lang_nl&ie=UTF-8&oe=UTF-8&selm=9402100649.AA13033%40spot.twinsun.com&rnum=1
but I would expect that after all most 10 years the problem had been fixed.

A simpler solution would be to set the LOGNAME variable to user2 
somewhere. I've understood that the differences are mainly historical.
This seems to me an ugly work arround that may leed to problems 
elsewhere, so I prefer a more elegant solution.

Any help would be appriciated.
Pepijn Kenter.

Re: GNU emacs locks files modified with CVS

[Kevin Rodgers]

Pepijn Kenter wrote:

> When loged in as user1 type:
> su user2
> emacs file.pro # edit, exit and save the changes
> emacs file.pro # file.pro is now read only.
> 
> I can not edit file.pro the second time because it is apperently locked 
> by user2 (as shown in the status line? of emacs). File permissions are 
> correct and the onwner of file.pro (still) is user2.
> 
> After some googling I think the possible cause is that emacs is 
> inconsistent in the way it handles the USER and LOGNAME variables.
> Indeed USER is set to user2 whereas LOGNAME is still user1. When I 
> change LOGNAME to user2 the problem disappears.
> 
> So, what to do?

If you want a login shell as user2, use `su - user2`.

-- 
Kevin Rodgers

Re: GNU emacs locks files modified with CVS

[Pepijn Kenter]

Kevin Rodgers wrote:
> Pepijn Kenter wrote:
> 
>> When loged in as user1 type:
>> su user2
>> emacs file.pro # edit, exit and save the changes
>> emacs file.pro # file.pro is now read only.
>>
>> I can not edit file.pro the second time because it is apperently 
>> locked by user2 (as shown in the status line? of emacs). File 
>> permissions are correct and the onwner of file.pro (still) is user2.
>>
>> After some googling I think the possible cause is that emacs is 
>> inconsistent in the way it handles the USER and LOGNAME variables.
>> Indeed USER is set to user2 whereas LOGNAME is still user1. When I 
>> change LOGNAME to user2 the problem disappears.
>>
>> So, what to do?
> 
> 
> If you want a login shell as user2, use `su - user2`.
> 

I'm sorry, I should have mentioned that I tried that, but then my 
DISPLAY environment variable is not set so I can not use the graphical 
emacs. I can, of course, set DISPLAY manually but it would be a nuisance 
to do that every time I log in as user2.

It's not quit clear to me when I should use a login shell and when not. 
IMO the bash documentation only explaines the differences, not why the 
different shells exist.

I'm guessing the solution will involve tweeking my system, not my emacs 
settings, so I probably should go to another newsgroup. Still, any help 
from here would be appreciated.

E.g. where is the DISPLAY variable set normally (when I log in as 
user1)? I'm using debian linux.

Pepijn Kenter.

Re: GNU emacs locks files modified with CVS

[gebser]

There's two ways which will keep/set the DISPLAY variable:

First, if the DISPLAY variable is set in user1 and you do "su user2", 
then the environment of user1 will carry into user2.  IOW, you're good. 

Second, if you, instead, do "su - user2", then you will have a fresh 
environment, that of user2.  If user2's environment doesn't have the 
DISPLAY variable set properly, you can do this by setting this in 
user2's ~/.bashrc file... if user2's default shell is bash-- if you're 
using some other shell, consult the manpage for the proper file and 
command syntax for setting the environment.


hth,
ken

At 10:44 (UTC+0100) on Tue, 16 Dec 2003 Pepijn Kenter said:

= Kevin Rodgers wrote:
= > Pepijn Kenter wrote:
= > 
= >> When loged in as user1 type:
= >> su user2
= >> emacs file.pro # edit, exit and save the changes
= >> emacs file.pro # file.pro is now read only.
= >>
= >> I can not edit file.pro the second time because it is apperently 
= >> locked by user2 (as shown in the status line? of emacs). File 
= >> permissions are correct and the onwner of file.pro (still) is user2.
= >>
= >> After some googling I think the possible cause is that emacs is 
= >> inconsistent in the way it handles the USER and LOGNAME variables.
= >> Indeed USER is set to user2 whereas LOGNAME is still user1. When I 
= >> change LOGNAME to user2 the problem disappears.
= >>
= >> So, what to do?
= > 
= > 
= > If you want a login shell as user2, use `su - user2`.
= > 
= 
= I'm sorry, I should have mentioned that I tried that, but then my 
= DISPLAY environment variable is not set so I can not use the graphical 
= emacs. I can, of course, set DISPLAY manually but it would be a nuisance 
= to do that every time I log in as user2.
= 
= It's not quit clear to me when I should use a login shell and when not. 
= IMO the bash documentation only explaines the differences, not why the 
= different shells exist.
= 
= I'm guessing the solution will involve tweeking my system, not my emacs 
= settings, so I probably should go to another newsgroup. Still, any help 
= from here would be appreciated.
= 
= E.g. where is the DISPLAY variable set normally (when I log in as 
= user1)? I'm using debian linux.
= 
= Pepijn Kenter.
= 
= _______________________________________________
= Help-gnu-emacs mailing list
= Help-gnu-emacs@gnu.org
= http://mail.gnu.org/mailman/listinfo/help-gnu-emacs
= 

Re: GNU emacs locks files modified with CVS

[Pepijn Kenter]

gebser@speakeasy.net wrote:
> There's two ways which will keep/set the DISPLAY variable:
> 
> First, if the DISPLAY variable is set in user1 and you do "su user2", 
> then the environment of user1 will carry into user2.  IOW, you're good. 
> 
> Second, if you, instead, do "su - user2", then you will have a fresh 
> environment, that of user2.  If user2's environment doesn't have the 
> DISPLAY variable set properly, you can do this by setting this in 
> user2's ~/.bashrc file... if user2's default shell is bash-- if you're 
> using some other shell, consult the manpage for the proper file and 
> command syntax for setting the environment.
> 
> 
Thanks for your reply but the .bashrc seems to me the wrong place to set 
the DISPLAY variable.
If you login from another machine it won't be set properly.

Pepijn.

Re: GNU emacs locks files modified with CVS

[gebser]

At 15:51 (UTC+0100) on Tue, 16 Dec 2003 Pepijn Kenter said:

= gebser@speakeasy.net wrote:
= > There's two ways which will keep/set the DISPLAY variable:
= > 
= > First, if the DISPLAY variable is set in user1 and you do "su user2", 
= > then the environment of user1 will carry into user2.  IOW, you're good. 
= > 
= > Second, if you, instead, do "su - user2", then you will have a fresh 
= > environment, that of user2.  If user2's environment doesn't have the 
= > DISPLAY variable set properly, you can do this by setting this in 
= > user2's ~/.bashrc file... if user2's default shell is bash-- if you're 
= > using some other shell, consult the manpage for the proper file and 
= > command syntax for setting the environment.
= > 
= > 
= Thanks for your reply but the .bashrc seems to me the wrong place to set 
= the DISPLAY variable.
= If you login from another machine it won't be set properly.
= 
= Pepijn.

Obviously you have to edit the ~/.bashrc file on the box and for the 
account you're logging into.  If it doesn't work, you're doing something 
wrong.  Do you know that you're using the bash shell?  If so, do "man 
bash" and it'll tell you about .bashrc and setting env vars.


ken

Re: GNU emacs locks files modified with CVS

[Maurizio Loreti]

Pepijn Kenter <kenter_remove_spam@tpd.tno.nl> writes:

> gebser@speakeasy.net wrote:
> > There's two ways which will keep/set the DISPLAY variable:
> > First, if the DISPLAY variable is set in user1 and you do "su
> > user2", then the environment of user1 will carry into user2.  IOW,
> > you're good. Second, if you, instead, do "su - user2", then you will
> > have a fresh environment, that of user2.  If user2's environment
> > doesn't have the DISPLAY variable set properly, you can do this by
> > setting this in user2's ~/.bashrc file... if user2's default shell
> > is bash-- if you're using some other shell, consult the manpage for
> > the proper file and command syntax for setting the environment.
> >
> Thanks for your reply but the .bashrc seems to me the wrong place to
> set the DISPLAY variable.
> If you login from another machine it won't be set properly.

Correct.  The right place is .bash_profile, executed at login.

FWIW, this is from my own .bash_profile:

,-----
| # Tries to figure out a correct DISPLAY environment variable
| 
| if [ -n "$DISPLAY" ]
| then
|   # if DISPLAY is set, we assume it is also valid; if it is not,
|   # the user may always change it later ($DISPLAY is printed at
|   # the end of the login procedure).
| 
|   REMOTE="${DISPLAY%%:*}"
| else
|   temp0=$(who am i | awk '{print $2}')
|   
|   if [ "$temp0" = "console" ]
|   then
|     REMOTE="localhost"
|     DISPLAY=":0.0"
|   else
|     temp1=$(who --lookup | grep "$temp0 " | uniq | awk '{print $6}')
|     # Note the blank-------------------^
|     if [ -n "$temp1" ]
|     then
|       temp2=$(echo $temp1 | sed -e 's/(//' -e 's/)//')
|       temp3=$(echo $temp2 | cut -d. -f2)
|       if [ "$temp3" = "pd" ]
|       then
|         # If on host.pd.infn.it, DISPLAY="host:0.0";
|         # if not, DISPLAY="host.dom.ain:0.0"
|         REMOTE=$(echo $temp2 | cut -d. -f1)
|       else
|         REMOTE="${temp2%%:*}"
|       fi
|       DISPLAY="${REMOTE}:0.0"
|       unset temp2 temp3
|     else
|       REMOTE=""
|       DISPLAY=":0.0"
|     fi
|     unset temp1
|   fi
|   unset temp0
| fi
| 
| export REMOTE DISPLAY
| echo "DISPLAY is now: $DISPLAY"
`-----

-- 
Maurizio Loreti                         http://www.pd.infn.it/~loreti/mlo.html
Dept. of Physics, Univ. of Padova, Italy              ROT13: ybergv@cq.vasa.vg

Re: GNU emacs locks files modified with CVS

[gebser]

Of course everyone can set up their systems however they wish, but I 
use:

export DISPLAY=$(who -lum|awk -F '(' '{print $2}'|awk -F ')' '{print $1}'):0

in my ~/.bashrc and have no problem logging in and/or running remotely
whatever X apps I want.

Because it would take a lot of thinking to hash out which is the correct 
file to put this in, whether the DISPLAY is a resource or not, whether 
this variable should be set for all interactive shells or just for 
logins, and because I don't wish to argue any of this, I'll just say 
that I disagree and believe that .bashrc *is* the proper place for 
setting DISPLAY.  As said at the outset, everyone can set up their 
systems however they wish.


hth,
ken


At 07:42 (UTC+0100) on 17 Dec 2003 Maurizio Loreti said:

= Pepijn Kenter <kenter_remove_spam@tpd.tno.nl> writes:
= 
= > gebser@speakeasy.net wrote:
= > > There's two ways which will keep/set the DISPLAY variable:
= > > First, if the DISPLAY variable is set in user1 and you do "su
= > > user2", then the environment of user1 will carry into user2.  IOW,
= > > you're good. Second, if you, instead, do "su - user2", then you will
= > > have a fresh environment, that of user2.  If user2's environment
= > > doesn't have the DISPLAY variable set properly, you can do this by
= > > setting this in user2's ~/.bashrc file... if user2's default shell
= > > is bash-- if you're using some other shell, consult the manpage for
= > > the proper file and command syntax for setting the environment.
= > >
= > Thanks for your reply but the .bashrc seems to me the wrong place to
= > set the DISPLAY variable.
= > If you login from another machine it won't be set properly.
= 
= Correct.  The right place is .bash_profile, executed at login.
= 
= FWIW, this is from my own .bash_profile:
= 
= ,-----
= | # Tries to figure out a correct DISPLAY environment variable
= | 
= | if [ -n "$DISPLAY" ]
= | then
= |   # if DISPLAY is set, we assume it is also valid; if it is not,
= |   # the user may always change it later ($DISPLAY is printed at
= |   # the end of the login procedure).
= | 
= |   REMOTE="${DISPLAY%%:*}"
= | else
= |   temp0=$(who am i | awk '{print $2}')
= |   
= |   if [ "$temp0" = "console" ]
= |   then
= |     REMOTE="localhost"
= |     DISPLAY=":0.0"
= |   else
= |     temp1=$(who --lookup | grep "$temp0 " | uniq | awk '{print $6}')
= |     # Note the blank-------------------^
= |     if [ -n "$temp1" ]
= |     then
= |       temp2=$(echo $temp1 | sed -e 's/(//' -e 's/)//')
= |       temp3=$(echo $temp2 | cut -d. -f2)
= |       if [ "$temp3" = "pd" ]
= |       then
= |         # If on host.pd.infn.it, DISPLAY="host:0.0";
= |         # if not, DISPLAY="host.dom.ain:0.0"
= |         REMOTE=$(echo $temp2 | cut -d. -f1)
= |       else
= |         REMOTE="${temp2%%:*}"
= |       fi
= |       DISPLAY="${REMOTE}:0.0"
= |       unset temp2 temp3
= |     else
= |       REMOTE=""
= |       DISPLAY=":0.0"
= |     fi
= |     unset temp1
= |   fi
= |   unset temp0
= | fi
= | 
= | export REMOTE DISPLAY
= | echo "DISPLAY is now: $DISPLAY"
= `-----
= 
= 

Re: GNU emacs locks files modified with CVS

[Kevin Rodgers]

gebser@speakeasy.net wrote:

> Of course everyone can set up their systems however they wish, but I 
> use:
> 
> export DISPLAY=$(who -lum|awk -F '(' '{print $2}'|awk -F ')' '{print $1}'):0
> 
> in my ~/.bashrc and have no problem logging in and/or running remotely
> whatever X apps I want.


I know this isn't comp.unix.shell, but that pipe can be simplified a little by
passing a regex as awk's field separator:


export DISPLAY=$(who -lum | awk -F'[()]' '{print $(NF-1)}'):0

-- 
Kevin Rodgers

Re: GNU emacs locks files modified with CVS

[Pepijn Kenter]

gebser@speakeasy.net wrote:
> Of course everyone can set up their systems however they wish, but I 
> use:

Of course. When saying the .bashrc isn't the proper place for setting 
the DISPLAY variable, I meant that at that time you can't know what 
value to set it to. From your (and Maurizio Loreti's) post I learned you 
can use the who command to find out. So thank you both.

> 
> export DISPLAY=$(who -lum|awk -F '(' '{print $2}'|awk -F ')' '{print $1}'):0
> 
> in my ~/.bashrc and have no problem logging in and/or running remotely
> whatever X apps I want.
> 
> Because it would take a lot of thinking to hash out which is the correct 
> file to put this in, whether the DISPLAY is a resource or not, whether...<snip>

Excuse my ignorance, but what do you mean by resource in this context?

Pepijn.

Re: GNU emacs locks files modified with CVS

[Maurizio Loreti]

gebser@speakeasy.net writes:

> Because it would take a lot of thinking to hash out which is the correct 
> file to put this in, whether the DISPLAY is a resource or not, whether 
> this variable should be set for all interactive shells or just for 
> logins, and because I don't wish to argue any of this, I'll just say 
> that I disagree and believe that .bashrc *is* the proper place for 
> setting DISPLAY.  As said at the outset, everyone can set up their 
> systems however they wish.

You are free to do a lot of things - to shoot yourself in a foot, if
you like.  I dare to dissent.  From 'man bash':

,-----
| When bash is invoked as an interactive login shell ...  it first reads
| and executes commands from the file /etc/profile, if that file exists.
| After reading that file, it looks for ~/.bash_profile, ~/.bash_login,
| and ~/.profile, in that order, and reads and executes commands from
| the first one that exists and is readable.
| ...
| When an interactive shell that is not a login shell is started, bash
| reads and executes commands from ~/.bashrc, if that file exists.
`-----

Since all non-login shells (used e.g. to run commands in a subshell)
inherit the environment from the common ancestor, the login shell, I
think it is just a loss of time to recompute every time an environment
variable that *cannot* have been changed.  YMMV, of course.

-- 
Maurizio Loreti                         http://www.pd.infn.it/~loreti/mlo.html
Dept. of Physics, Univ. of Padova, Italy              ROT13: ybergv@cq.vasa.vg

Re: GNU emacs locks files modified with CVS

[gebser]

I wrote that a long time ago when my awk skills were about nil.  This 
was the first time looking at it again in a long, long while.  But 
thanks.   

ken

At 09:26 (UTC-0700) on Wed, 17 Dec 2003 Kevin Rodgers said:

= gebser@speakeasy.net wrote:
= 
= > Of course everyone can set up their systems however they wish, but I 
= > use:
= > 
= > export DISPLAY=$(who -lum|awk -F '(' '{print $2}'|awk -F ')' '{print $1}'):0
= > 
= > in my ~/.bashrc and have no problem logging in and/or running remotely
= > whatever X apps I want.
= 
= 
= I know this isn't comp.unix.shell, but that pipe can be simplified a little by
= passing a regex as awk's field separator:
= 
= 
= export DISPLAY=$(who -lum | awk -F'[()]' '{print $(NF-1)}'):0
= 
= 

Re: GNU emacs locks files modified with CVS

[Kevin Rodgers]

Maurizio Loreti wrote:

> gebser@speakeasy.net writes:
> 
> 
>>Because it would take a lot of thinking to hash out which is the correct 
>>file to put this in, whether the DISPLAY is a resource or not, whether 
>>this variable should be set for all interactive shells or just for 
>>logins, and because I don't wish to argue any of this, I'll just say 
>>that I disagree and believe that .bashrc *is* the proper place for 
>>setting DISPLAY.  As said at the outset, everyone can set up their 
>>systems however they wish.
>>
> 
> You are free to do a lot of things - to shoot yourself in a foot, if
> you like.  I dare to dissent.  From 'man bash':
> 
> ,-----
> | When bash is invoked as an interactive login shell ...  it first reads
> | and executes commands from the file /etc/profile, if that file exists.
> | After reading that file, it looks for ~/.bash_profile, ~/.bash_login,
> | and ~/.profile, in that order, and reads and executes commands from
> | the first one that exists and is readable.
> | ...
> | When an interactive shell that is not a login shell is started, bash
> | reads and executes commands from ~/.bashrc, if that file exists.
> `-----
> 
> Since all non-login shells (used e.g. to run commands in a subshell)
> inherit the environment from the common ancestor, the login shell, I
> think it is just a loss of time to recompute every time an environment
> variable that *cannot* have been changed.  YMMV, of course.

Right.  So ~/.bash_profile, ~/.bash_login, or ~/.profile is the right place
to set DISPLAY.

-- 
Kevin Rodgers