Execute at login

[Helmut Schneider]

Polytropon wrote:

> On Mon, 26 Sep 2011 20:41:43 +0000 (UTC), Helmut Schneider wrote:
> > Hi,
> > 
> > which options do I have to execute at login?
> > 
> > I would like to implement something like update-motd [1] without
> > actually modifying /etc/motd. The code snippet is
> > 
> > if [ -d /etc/motd.d ]; then
> >   for FILE in /etc/motd.d/*; do
> >     [ -x ${FILE} ] && ${FILE}
> >   done
> > fi
> > 
> > It should be executed for all users but only at login (regardless if
> > she/he logs in via console or ssh). It also should be independent of
> > the login shell. Therefore neither /etc/profile nor ~/.profile nor
> > ~/.login seem suitable.
> > 
> > Where can I put that code? The content of /etc/motd.d/ can change
> > anytime.
> 
> I'm not sure if this works, but maybe something like this
> can be an idea to create a comparable solution:
> 
> You can (ab)use the "login shell" property of /etc/passwd
> to give all users a login shell that is the above script
> which then executes the real login shell for the users
> (I assume this will be either bash or csh).
> 
> See "man 5 passwd" for details.
> 
> However, this approach can cause trouble in combination with
> chsh. It also doesn't seem to be limited to interactive logins,
> so there should be some test in the script to check if the
> current shell is in dialog mode
> 
> For csh, this can be done by
> 
> 	if ($?prompt) then
> 		... interactive shell stuff ...
> 	endif
> 
> But again, this does not apply to different login shells.
> 
> An idea to compensate this could be to employ login.conf
> instead, per the "shell" environmental setting. This seems
> to override the shell defined in /etc/passwd (which can be
> subject to a chsh call).
> 
> See "man 5 login.conf" for details.
> 
> The script mentioned above could therefore include the
> following steps:
> 
> 	1. determinate kind of shell:
> 	   in case of interactive shell, continue
> 
> 	2. check for motd.d functionality:
> 	   if /etc/motd.d/ exists and has executable files
> 	   in it, execute them (basically your script concept)
> 
> 	3. determine user's dialog shell
> 	   read /etc/passwd and start the user's dialog shell
> 	   by exec <shellname>
> 
> You can write this in any (shell) script language you want.
> I would suggest plain #!/bin/sh syntax.

Thanks for that, but I prefer a "straighter" way. :) It seems someone
had the same idea before:

<http://cvsup6.freebsd.org/pub/FreeBSD/development/FreeBSD-CVS/src/contrib/libpam/modules/pam_motd/Attic/>

Anyone knows why it was discontinued?