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Date: Tue, 15 Nov 2011 23:54:33 +0100
From: Cyrille Lefevre <cyrille DOT lefevre-lists AT laposte DOT net>
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To: cygwin AT cygwin DOT com, David Sastre <d DOT sastre DOT medina AT gmail DOT com>
Subject: Re: Why 'script' utility require SHELL (and work fine under Linux)?
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Le 08/11/2011 00:25, Cyrille Lefevre a écrit :

Hi,

are you working on these issues ?

thanks in advance.

> Le 04/11/2011 21:22, David Sastre a écrit :
>> On Fri, Nov 04, 2011 at 06:05:39AM +0100, Cyrille Lefevre wrote:
>>> the base-file maintainer has been BCC'ed to add the export SHELL to
>>> the /etc/profile.
>>
>> GNU/Linux login sets SHELL to bash, mksh, ... whilst ssh sets SHELL to
>> /bin/bash, /bin/posh, /bin/mksh ...
>> Given that there is no real login into cygwin (yet?), SHELL should be
>> set to the expected login value.
>>
>> Assuming SHELL would be set and exported for login shells, i.e.,
>> further (nested) callings to interactive, non-login shells would
>> inherit the original (login) SHELL value (as in GNU/Linux):
>>
>> $ echo $SHELL
>> bash
>> $ mksh
>> $ echo $SHELL
>> bash
>>
>> It could be fixed for bash, zsh, and mksh. Even for nested
>> calls to login shells (which GNU/Linux doesn't honor) by setting SHELL
>> for every ifdef in /etc/profile. Collateral damage:
>>
>> -posh works OK if set as login shell in /etc/passwd, but it is broken
>> when called from command line as login shell (i.e. it ignores both
>> /etc/profile and ~/.profile)
>> -sh thinks she's bash:
>>
> <snip>
>>
>> In short: it's not clear to me how to add this functionality
>> consistently.
> Hi,
>
> well, you didn't understand what I mean, so,
> let's try w/ export | grep SHELL
>
> $ bash -l
> $ echo $SHELL
> /bin/bash
> => defaulted internally ?
> $ export -p | egrep 'SHELL|COMSPEC'
> export COMSPEC="C:\\Windows\\system32\\cmd.exe"
> => no env SHELL
> $ perl -MEnv -e 'print $SHELL.":".$COMSPEC'
> :C:\Windows\system32\cmd.exe
> $ awk 'BEGIN{print ENVIRON["SHELL"]":"ENVIRON["COMSPEC"]}'
> :C:\Windows\system32\cmd.exe
>
> ditto w/ sh (almost same as bash :-), however,
> defaulted to /bin/bash instead of /bin/sh !
>
> == posh ==
>
> $ posh -l
> $ echo $SHELL
> => no default !
> $ export -p | egrep 'SHELL|COMSPEC'
> export COMSPEC=C:\Windows\system32\cmd.exe
> export SHELL
> => empty !
> $ env | grep SHELL
> => nothing
>
> $ SHELL=/bin/bash posh -l
> $ echo $SHELL
> /bin/bash
> => ok
> $ export -p | egrep 'SHELL|COMSPEC'
> export COMSPEC=C:\Windows\system32\cmd.exe
> export SHELL=/bin/bash
>
> PS : you're right, posh is broken regarding /etc/profile, etc. w/ -l !
>
> == mksh ==
>
> $ mksh -l
> $ echo $SHELL
> => no default !
> $ export -p | egrep 'SHELL|COMSPEC'
> export COMSPEC='C:\Windows\system32\cmd.exe'
> export SHELL
> => empty !
> $ env | grep SHELL
> => nothing
>
> $ SHELL=/bin/bash mksh -l
> $ echo $SHELL
> /bin/bash
> => ok
> $ export -p | egrep 'SHELL|COMSPEC'
> export COMSPEC='C:\Windows\system32\cmd.exe'
> export SHELL=/bin/bash
>
> == dash ==
>
> same as mksh
>
> == zsh ==
>
> $ zsh -l
> $ echo $SHELL
> /bin/zsh
> => defaulted to /bin/zsh through /etc/profile.d/zshell.zsh
> $ export | egrep 'SHELL|COMSPEC'
> COMSPEC='C:\Windows\system32\cmd.exe'
> SHELL=/bin/zsh
>
> $ SHELL=/bin/bash zsh -l
> $ echo $SHELL
> /bin/bash
> => ok
> $ export | egrep 'SHELL|COMSPEC'
> COMSPEC='C:\Windows\system32\cmd.exe'
> SHELL=/bin/bash
>
> == ksh93 ==
>
> $ ksh93 -l
> $ echo $SHELL
> /bin/sh
> => defaulted to /bin/sh instead of /path/to/ksh93 !
> $ export | egrep 'SHELL|COMSPEC'
> COMSPEC='C:\Windows\system32\cmd.exe'
> => no env SHELL
>
> $ SHELL=/bin/bash ksh93 -l
> $ echo $SHELL
> /bin/bash
> => ok
> $ export -p | egrep 'SHELL|COMSPEC'
> export COMSPEC='C:\Windows\system32\cmd.exe'
> export SHELL=/bin/bash
>
> == csh/tcsh ==
>
> $ csh -l
> $ echo $SHELL
> /bin/tcsh
> => defaulted to /bin/tcsh instead of /bin/csh through /etc/csh.login
> $ printenv | egrep 'SHELL|COMSPEC'
> COMSPEC=C:\Windows\system32\cmd.exe
> SHELL=/bin/tcsh
>
> $ SHELL=/bin/bash csh -l
> $ echo $SHELL
> /bin/tcsh
> => ko, $SHELL shouldn't be set irreparably in /etc/csh.login
> if ( ! ${?SHELL} ) then
> setenv SHELL $shell
> endif
>
> so, export SHELL could be added to /etc/profile, isn't it ?
>
> also, about mksh vs pdksh :
> case $KSH_VERSION in *MIR*) SHELL=/bin/mksh ;; *) SHELL=/bin/ksh ;; esac
>
> PS : mail from 31/03/2011, but it may not rich you ?
>
> profile_d shouldn't set LC_COLLATE irreparably and should unset file :
>
> would it be possible to change :
>
> profile_d ()
> {
> saved_LC_COLLATE=${LC_COLLATE}
> LC_COLLATE=C
> for file in /etc/profile.d/*.$1; do
> [ -e "${file}" ] && . "${file}"
> done
> LC_COLLATE=${saved_LC_COLLATE}
> unset saved_LC_COLLATE
> }
>
> to :
>
> profile_d ()
> {
> for file in $(export LC_COLLATE=C; echo /etc/profile.d/*.$1); do
> [ -e "${file}" ] && . "${file}"
> done
> unset file
> }
>
> PS1 *must not* be exported.
>
> historically, it is not exported to know if it is a shell is interactive
> or not since only interactive shells set it.
>
> i.e., the following both solutions are equivalent.
>
> case $- in *i*) interactive ;; esac
> [ -n $PS1 ] && interactive
>
> if PS1 is exported, it is always set for subshells and this may cause
> trouble in some script.
>
> also, from man bash :
>
> An interactive shell is one started without non-option arguments and
> without the -c option whose standard input and error are both connected
> to terminals (as determined by isatty(3)), or one started with the -i
> option. PS1 is set and $- includes i if bash is interactive, allowing
> a shell script or a startup file to test this state.
>
> well, you answer me about that :
>
>  >> What the man page doesn't tell you is that bash actually unsets PS1
> if the
>  >> shell isn't interactive, so for bash at least, exporting PS1 can't
> cause a
>  >> problem.
>
> then, I reply :
>
>  > thanks for the tip, however, this is not an expected behaviour...
>
> also, what about other shells ? exporting PS1 broke this behavious.
>
> PS again : english isn't my natural language, so, forgive me if I'm too
> rough :-)


Regards,

Cyrille Lefevre
-- 
mailto:Cyrille DOT Lefevre-lists AT laposte DOT net


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