Date: Fri, 21 Aug 1998 15:34:36 -0400 (EDT) From: CyberPeasant <djv@bedford.net> To: romank@graphnet.com (Roman Katsnelson) Cc: freebsd-questions@FreeBSD.ORG Subject: Re: "clear" curiosity Message-ID: <199808211934.PAA29879@lucy.bedford.net> In-Reply-To: <35DDC102.CE22AD57@graphnet.com> from Roman Katsnelson at "Aug 21, 98 02:48:34 pm"
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Roman Katsnelson wrote:
> Hi,
>
> I did 'cat clear' recently, and saw that all it said was
>
> exec tput clear
>
> I noticed that when I just type that in at the command line, the result
> is entirely different -- it logs me out, clears the screen and gives a
> new login prompt. I like this a lot better than the regular "exit" or
> "Ctrl-D" thing because it clears the screen first. These are my two
> questions:
>
> 1) Why are the results different between the same commands in a shell
> script and at the command line?
> and
Well, exec replaces the current program with the other one. (tput in
this case.)
If it's a shell script, (e.g. clear) exec replaces the sh running
the script with tput.
>From the command line, it replaces your login shell.
> 2) How can I write a shell script that does the same thing? (I tried,
> but, of course, it did exactly what 'clear' does).
for reasons, see the preceding.
Bash has a .bash_logout script, maybe other shells do.
This is the sort of thing you need to do on a system where you are
not rooted.
Usually, a better way is to have getty clear the screen.
Adding a "\f" to the login banner sequence in /etc/gettytab seems
to do the trick.
Before:
default:\
:cb:ce:ck:lc:fd#1000:im=\r\nFreeBSD (%h) (%t)\r\n\r\n:sp#1200:
After:
default:\
:cb:ce:ck:lc:fd#1000:im=\f\r\nFreeBSD (%h) (%t)\r\n\r\n:sp#1200:
Note that this will affect all getty'ed logins: console, serial
lines. (But not telnet and rlogin. These can be dealt with as
well, I think, but am too lazy to dig it out.) Maybe some terminal
types will choke on the \f.
Dave
--
Confutatis maledictis, flammis acribus addictis.
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