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Subject: Re: Terminal output disappearing after SSH into cygwin
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From: Ken Brown via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Ken Brown <kbrown AT cornell DOT edu>
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On 1/22/2021 3:16 AM, Brian Inglis wrote:
> On 2021-01-21 09:02, matthew patton via Cygwin wrote:
>> On Thursday, January 21, 2021, 10:49:14 AM EST, Martyn B wrote:
>>> On 2021-01-21 11:13, Ken Brown via Cygwin wrote:
>>>> There's also /etc/bash.bash_logout.  The default version of that clears the 
>>>> screen:
>>>>
>>>> $ cat /etc/defaults/etc/bash.bash_logout
>>>> [...]
>>>> # base-files version 4.3-2
>>>>
>>>> # /etc/bash.bash_logout: executed by bash(1) when login shell exits.
>>>>
>>>> # The latest version as installed by the Cygwin Setup program can
>>>> # always be found at /etc/defaults/etc/bash.bash_logout
>>>>
>>>> # Modifying /etc/bash.bash_logout directly will prevent
>>>> # setup from updating it.
>>>>
>>>> # System-wide bashrc file
>>>>
>>>> # when leaving the console clear the screen to increase privacy
>>>> if [ "$SHLVL" = 1 ]; then
>>>>    [ -x /usr/bin/clear ] && /usr/bin/clear
>>>> fi
> 
>>> 1) understand why this happens. - Is this the Cygwin standard behavior?
> 
>> Not in the slightest.
> 
> It appears to be so:
> 
> $ cygcheck -f /etc/defaults/etc/bash.bash_logout
> base-files-4.3-2
> $ ls /etc/**/*bash_logout
> /etc/bash.bash_logout  /etc/defaults/etc/bash.bash_logout
> $ zgrep bash_logout /etc/**/base-files*
> /etc/preremove/base-files-manifest.lst:etc/bash.bash_logout
> /etc/setup/base-files.lst.gz:etc/defaults/etc/bash.bash_logout
> 
> Whether it should be is a good question.
> 
> There's no /etc/bash_logout file under Debian, etc. but /etc/skel/.bash_logout 
> and ~/.bash_logout also have the same clear screen code.
> 
> Is (or was) /etc/bash.bash_logout that did this in the bash sources or under 
> Fedora, which is the Linux basis for some Cygwin approaches, behaviour, and 
> conventions?

There are two separate issues here.  The first is that Cygwin's bash executes 
/etc/bash.bash_logout.  The second is that the default /etc/bash.bash_logout 
clears the screen.

The first issue is dealt with in the bash sources.  It is an option that is 
disabled by default, but Cygwin's bash maintainer chose to enable it.  That's 
done in the following hunk from bash-4.4.12-3.src.patch:

--- origsrc/bash-4.4/config-top.h	2016-05-19 13:34:02.000000000 -0500
+++ src/bash-4.4/config-top.h	2017-01-27 13:11:50.793821100 -0600
@@ -87,10 +87,10 @@
  #define DEFAULT_BASHRC "~/.bashrc"

  /* System-wide .bashrc file for interactive shells. */
-/* #define SYS_BASHRC "/etc/bash.bashrc" */
+#define SYS_BASHRC "/etc/bash.bashrc"

  /* System-wide .bash_logout for login shells. */
-/* #define SYS_BASH_LOGOUT "/etc/bash.bash_logout" */
+#define SYS_BASH_LOGOUT "/etc/bash.bash_logout"

  /* Define this to make non-interactive shells begun with argv[0][0] == '-'
     run the startup files when not in posix mode. */

I've added Eric to the CC in case he wants to comment.

I don't know the history of the second issue, but that's a matter for Achim as 
base-files maintainer.

Ken
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