ch05_03.htm

the unix power tools

> variable (<A
CLASS="linkend"
HREF="ch05_04.htm"
TITLE="Setting the TERMCAP Variable with tset "
>5.4</A
>)</SPAN
>.
(You must also issue the command <CODE
CLASS="literal"
>set noglob</CODE
>,
as explained in article
<A
CLASS="xref"
HREF="ch06_09.htm"
TITLE="Special C Shell Variables "
>6.9</A
>.)</P
><P
CLASS="para"
>To see what <EM
CLASS="emphasis"
>tset</EM
> can do, consider a case where the terminal's serial
line is connected to a dialup modem, through which several different
users might be connected, each using a different type of
terminal.
Accordingly, the default terminal type in
<EM
CLASS="emphasis"
>/etc/ttytype</EM
> should be set to <EM
CLASS="emphasis"
>dialup</EM
>.
The <EM
CLASS="emphasis"
>tset</EM
> command could

then be used in
the <EM
CLASS="emphasis"
>.login</EM
> file as follows, with the appropriate terminal type
set for each user:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>set noglob
eval `tset -s -Q -m 'dialup:vt100'`</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-4940"
></A
>This means that if <EM
CLASS="emphasis"
>ttytype</EM
> says <EM
CLASS="emphasis"
>dialup</EM
>, use
<EM
CLASS="emphasis"
>vt100</EM
> as the terminal type. A colon separates the
<EM
CLASS="emphasis"
>ttytype</EM
> value and the value to which it is to be mapped.
If a user wants to be prompted to be sure, place a question 
mark after the colon and before the mapped terminal type:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>set noglob
eval `tset -s -Q -m 'dialup:?vt100'`</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>The prompt will look like this:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>TERM = (vt100)</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>If the user presses  
RETURN,
the preferred terminal type will be used. Alternatively, another
terminal type could be entered at that time.</P
><P
CLASS="para"
>You can cause <EM
CLASS="emphasis"
>tset</EM
> to prompt for a terminal type
even without testing a generic entry like <EM
CLASS="emphasis"
>dialup</EM
>.
Just specify the desired terminal type, preceded by a question mark,
after the <EM
CLASS="emphasis"
>-m</EM
> option.
For example:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>set noglob
eval `tset -s -Q -m '?vt100'`</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>It is also possible to specify different terminal types for
different line speeds. Say, for
example, that you normally used a Wyse-50 with a 9600-bps
modem when dialing in from home, but used a portable PC with
a VT100 terminal emulator and 2400-bps modem when you were
on the road. You might then use a <EM
CLASS="emphasis"
>tset</EM
> command like this:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>set noglob
eval `tset -s -Q -m 'dialup@2400:vt100' wy50`</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>&#13;Assuming that the type is set in <EM
CLASS="emphasis"
>ttytype</EM
> as <EM
CLASS="emphasis"
>dialup</EM
>, 
<EM
CLASS="emphasis"
>tset</EM
> will use the type <EM
CLASS="emphasis"
>vt100</EM
> if at 2400 bps
and, if not, will use the type <EM
CLASS="emphasis"
>wy50</EM
>.</P
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-4970"
></A
>[Watch out for the linespeed switches.
They don't work on a lot of networked systems&nbsp;- usually, the line speed
at the computer's port is higher than the speed at the terminal.
The same problem occurs, these days, with dialup modems that use data
compression. <EM
CLASS="emphasis"
>-JP</EM
>&nbsp;]
Various symbols can be used for line-speed calculations: &#13;</P
><DL
CLASS="variablelist"
><DT
CLASS="term"
><CODE
CLASS="literal"
>@</CODE
><CODE
CLASS="replaceable"
><I
>speed</I
></CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-4980"
></A
>Means at the specified speed. </P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>&lt;</CODE
><CODE
CLASS="replaceable"
><I
>speed</I
></CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
>Means less than the specified speed.</P
></DD
><DT
CLASS="term"
><CODE
CLASS="literal"
>&gt;</CODE
><CODE
CLASS="replaceable"
><I
>speed</I
></CODE
></DT
><DD
CLASS="listitem"
><P
CLASS="para"
>Means greater than the specified speed. &#13;</P
></DD
></DL
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-4995"
></A
>An exclamation point can precede the
operator to reverse the sense of the comparison.
(For example,
<CODE
CLASS="literal"
>!@1200</CODE
> would mean at any speed other than 1200 bps.
In the C shell, you have to type
<SPAN
CLASS="link"
><CODE
CLASS="literal"
>\!@1200</CODE
> (<A
CLASS="linkend"
HREF="ch11_02.htm"
TITLE="History in a Nutshell "
>11.2</A
>)</SPAN
>
instead.)</P
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-5002"
></A
>Multiple <EM
CLASS="emphasis"
>-m</EM
> options can be specified; the first map to be
satisfied will be used. If no match is found, a final value
specified on the line without a <EM
CLASS="emphasis"
>-m</EM
> option (as in the above 
example) will be used. If no value is specified, the type
in <EM
CLASS="emphasis"
>/etc/ttytype</EM
> will be used.</P
><P
CLASS="para"
>These changes may not always work; article
<A
CLASS="xref"
HREF="ch42_03.htm"
TITLE="Why Changing TERM Sometimes Doesn't Work "
>42.3</A
>
explains why.
Article
<A
CLASS="xref"
HREF="ch41_09.htm"
TITLE="Commands to Adjust Your Terminal "
>41.9</A
>
has a script for adjusting your terminal.</P
><DIV
CLASS="sect1info"
><P
CLASS="SECT1INFO"
>- <SPAN
CLASS="authorinitials"
>TOR</SPAN
> <SPAN
CLASS="bibliomisc"
>from O'Reilly &amp; Associates' <CITE
CLASS="citetitle"
>termcap &amp; terminfo</CITE
>, Chapter 4</SPAN
></P
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