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From: Oleksandr Gavenko <gavenkoa AT gmail DOT com>
Subject: Re: Why 'script' utility require SHELL (and work fine under  Linux)?
Date: Sun, 16 Oct 2011 20:07:42 +0300
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15.10.2011 0:47, Kaz Kylheku пишет:
>
>> So SHELL env var does not exported by bash...
>> Why?
>
> This is a bug in bash which hides broken behavior
> in the OS.
>
> Bash expects this to be an existing environment variable,
> and it usually is in normal Unix like operating systems.
>
> However, bash internally sets the variable if it is
> missing (without exporting it):
>
>  From "info bash".
>
>
> `SHELL'
> The full pathname to the shell is kept in this environment
> variable. If it is not set when the shell starts, Bash assigns to
> it the full pathname of the current user's login shell.
>
> It is correct not to export the variable. Bash might not be
> the user's shell, so it has no right to introduce itself as
> the SHELL to child processes.
>
> But, in fact, the shell does not own that variable at all
> and so it should not be setting it up even as an internal
> variable. The variable should stay unset to indicate
> that "there does not exist a configuration for the user's
> shell in this system".
> [...]
> Where does it come from on Linux? On the distro I have here,
> it is not exported by anything in /etc or my /home directory.
>
> Of course not. It comes from the "login" process which
> authenticates you and fetches your shell from the password
> file.
>
> Linux man page for "login":
>
> The value for $HOME, $SHELL, $PATH, $LOGNAME, and
> $MAIL are set according to the appropriate fields in
> the password entry.
>
> Cygwin sets HOME, and PATH, but not SHELL and LOGNAME.
>
Thanks for explanation. I set SHELL to /bin/bash under
control panel.

Also I set some another env var (place for info purpose):

   SHELL=/bin/bash
   # Emacs parser of external program output
   # does not expect warnings from Cygwin...
   CYGWIN=nodosfilewarning
   # To allow start X program anywhere when X started,
   # for example by Win+R
   DISPLAY=:0
   # Where live all profiles...
   HOME=e:\home
   # This allow access to info files from Cygwin and native Emacs...
   # Take special attention to final colon.
 
INFOPATH='c:/opt/cygwin/usr/share/info;e:/home/usr/share/info;e:/bin/gnuwin32/info;e:/bin/gnuwin32/share/info:'
   # This allow access to man files from Cygwin and native Emacs
   # (with cygwin-mount.el enabled)...
   # Take special attention to leading colon.
 
MANPATH=:/cygdrive/e/home/usr/share/man:/usr/share/man:/usr/local/share/man

Also 2 year ago I write personal note about why set SHELL to /bin/bash:
if do not do so rxvt use sh as shell and ~/.bashrc was not read
and I lose my personal settings.

But when I switch to mintty I forget about this as mintty start bash by 
default...


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