How to change the title of an xterm

How to change the title of an xterm
Ric Lister, [email protected]
v2.0, 27 October 1999

This document explains how to use escape sequences to dynamically
change window and icon titles of an xterm. Examples are given for sev
eral shells, and the appendix gives escape sequences for some other
terminal types.
______________________________________________________________________

Table of Contents

1. Where to find this document

2. Static titles

3. Dynamic titles

3.1 xterm escape sequences
3.2 Printing the escape sequences

4. Examples for different shells

4.1 zsh
4.2 tcsh
4.3 bash
4.4 ksh
4.5 csh

5. Printing the current job name

5.1 zsh
5.2 Other shells

6. Appendix: escapes for other terminal types

6.1 IBM
6.2 SGI
6.3 Sun
6.4 CDE
6.5 HPterm

7. Appendix: examples in other languages

7.1 C
7.2 Perl

8. Credits

______________________________________________________________________

1. Where to find this document

This document is now part of the Linux HOWTO Index
<http://sunsite.unc.edu/LDP/HOWTO/> and can be found at
<http://sunsite.unc.edu/LDP/HOWTO/mini/Xterm-Title.html>.

The latest version can always be found in several formats at
<http://www.giccs.georgetown.edu/~ric/howto/Xterm-Title/>.

This document supercedes the original howto written by Winfried
Trmper.

2. Static titles

A static title may be set for any of the terminals xterm, color-xterm
or rxvt, by using the -T and -n switches:

xterm -T "My XTerm's Title" -n "My XTerm's Icon Title"

3. Dynamic titles

Many people find it useful to set the title of a terminal to reflect
dynamic information, such as the name of the host the user is logged
into, the current working directory, etc.

3.1. xterm escape sequences

Window and icon titles may be changed in a running xterm by using
XTerm escape sequences. The following sequences are useful in this
respect:

ESC]0;stringBEL -- Set icon name and window title to string

ESC]1;stringBEL -- Set icon name to string

ESC]2;stringBEL -- Set window title to string

where ESC is the escape character (\033), and BEL is the bell
character (\007).

Printing one of these sequences within the xterm will cause the window
or icon title to be changed.

Note: these sequences apply to most xterm derivatives, such as nxterm,
color-xterm and rxvt. Other terminal types often use different
escapes; see the appendix for examples. For the full list of xterm
escape sequences see the file ctlseq2.txt
<http://www.giccs.georgetown.edu/~ric/howto/Xterm-Title/ctlseq2.txt>,
which comes with the xterm distribution, or xterm.seq
<http://www.giccs.georgetown.edu/~ric/howto/Xterm-Title/xterm.seq>,
which comes with the rxvt <http://www.rxvt.org/> distribution.

3.2. Printing the escape sequences

For information that is constant throughout the lifetime of this
shell, such as host and username, it will suffice to simply echo the
escape string in the shell rc file:

echo -n "\033]0;${USER}@${HOST}\007"

should produce a title like username@hostname, assuming the shell
variables $USER and $HOST are set correctly. The required options for
echo may vary by shell (see examples below).

For information that may change during the shell's lifetime, such as
current working directory, these escapes really need to be applied
every time the prompt changes. This way the string is updated with
every command you issue and can keep track of information such as
current working directory, username, hostname, etc. Some shells
provide special functions for this purpose, some don't and we have to
insert the title sequences directly into the prompt string. This is
illustrated in the next section.

4. Examples for different shells

Below we provide an set of examples for some of the more common
shells. We start with zsh as it provides several facilities that make
our job much easier. We will then progress through increasingly
difficult examples.

In all the examples we test the environment variable $TERM to make
sure we only apply the escapes to xterms. We test for $TERM=xterm*;
the wildcard is because some variants (such as rxvt) can set
$TERM=xterm-color.

We should make an extra comment about C shell derivatives, such as
tcsh and csh. In C shells, undefined variables are fatal errors.
Therefore, before testing the variable $TERM, it is necessary to test
for its existence so as not to break non-interactive shells. To
achieve this you must wrap the examples below in something like:

if ($?TERM) then
...
endif

(In our opinion this is just one of many reasons not to use C shells.
See Csh Programming Considered Harmful <http://language.perl.com/ver
sus/csh.whynot> for a useful discussion).

The examples below should be used by inserting them into the
appropriate shell initialisation file; i.e. one that is sourced by
interactive shells on startup. In most cases this is called something
like .shellrc (e.g. .zshrc, .tcshrc, etc).

4.1. zsh

zsh provides some functions and expansions, which we will use:

precmd () a function which is executed just before each prompt
chpwd () a function which is executed whenever the directory is changed
\e escape sequence for escape (ESC)
\a escape sequence for bell (BEL)
%n expands to $USERNAME
%m expands to hostname up to first '.'
%~ expands to directory, replacing $HOME with '~'

There are many more expansions available: see the zshmisc man page.

Thus, the following will set the xterm title to "username@hostname:
directory":

case $TERM in
xterm*)
precmd () {print -Pn "\e]0;%n@%m: %~\a"}
;;
esac

This could also be achieved by using chpwd() instead of precmd(). The
print builtin works like echo, but gives us access to the % prompt
escapes.

4.2. tcsh

tcsh has some functions and expansions similar to those of zsh:

precmd () a function which is executed just before each prompt
cwdcmd () a function which is executed whenever the directory is changed
%n expands to username
%m expands to hostname
%~ expands to directory, replacing $HOME with '~'
%# expands to '>' for normal users, '#' for root users
%{...%} includes a string as a literal escape sequence

Unfortunately, there is no equivalent to zsh's print command allowing
us to use prompt escapes in the title string, so the best we can do is
to use shell variables (in ~/.tcshrc):

switch ($TERM)
case "xterm*":
alias precmd 'echo -n "\033]0;${HOST}:$cwd\007"'
breaksw
endsw

However, this gives the directory's full path instead of using ~.
Instead you can insert the string in the prompt:
switch ($TERM)
case "xterm*":
set prompt="%{\033]0;%n@%m:%~\007%}tcsh%# "
breaksw
default:
set prompt="tcsh%# "
breaksw
endsw

which sets a prompt of "tcsh% ", and an xterm title and icon of "user
name@hostname: directory". Note that the "%{...%}" must be placed
around escape sequences (and cannot be the last item in the prompt:
see the tcsh man page for details).

4.3. bash

bash supplies a variable $PROMPT_COMMAND which contains a command to
execute before the prompt. This example sets the title to
username@hostname: directory:

PROMPT_COMMAND='echo -ne "\033]0;${USER}@${HOSTNAME}: ${PWD}\007"'

where \033 is the character code for ESC, and \007 for BEL.

Note that the quoting is important here: variables are expanded in
"...", and not expanded in '...'. So $PROMPT_COMMAND is set to an
unexpanded value, but the variables inside "..." are expanded when
$PROMPT_COMMAND is used.

However, $PWD produces the full directory path. If we want to use the
~ shorthand we need to embed the escape string in the prompt, which
allows us to take advantage of the following prompt expansions
provided by the shell:

\u expands to $USERNAME
\h expands to hostname up to first '.'
\w expands to directory, replacing $HOME with '~'
\$ expands to '$' for normal users, '#' for root
\[...\] embeds a sequence of non-printing characters

Thus, the following produces a prompt of bash$ , and an xterm title of
username@hostname: directory:

case $TERM in
xterm*)
PS1="\[\033]0;\u@\h: \w\007\]bash\\$ "
;;
*)
PS1="bash\\$ "
;;
esac

Note the use of \[...\], which tells bash to ignore the non-printing
control characters when calculating the width of the prompt. Otherwise
line editing commands get confused while placing the cursor.

4.4. ksh

ksh provides little in the way of functions and expansions, so we have
to insert the escape string in the prompt to have it updated
dynamically. This example produces a title of username@hostname:
directory and a prompt of ksh$ .

case $TERM in
xterm*)
HOST=`hostname`
PS1='^[]0;${USER}@${HOST}: ${PWD}^Gksh$ '
;;
*)
PS1='ksh$ '
;;
esac

However, $PWD produces the full directory path. We can remove the pre
fix of $HOME/ from the directory using the ${...##...} construct. We
can also use ${...%%...} to truncate the hostname:

HOST=`hostname`
HOST=${HOST%%.*}
PS1='^[]0;${USER}@${HOST}: ${PWD##${HOME}/}^Gksh$ '

Note that the ^[ and ^G in the prompt string are single characters for
ESC and BEL (can be entered in emacs using C-q ESC and C-q C-g).

4.5. csh

This is very difficult indeed in csh, and we end up doing something
like the following:

switch ($TERM)
case "xterm*":
set host=`hostname`
alias cd 'cd \!*; echo -n "^[]0;${user}@${host}: ${cwd}^Gcsh% "'
breaksw
default:
set prompt='csh% '
breaksw
endsw

where we have had to alias the cd command to do the work of sending
the escape sequence. Note that the ^[ and ^G in the string are single
characters for ESC and BEL (can be entered in emacs using C-q ESC and
C-q C-g).

Notes: on some systems hostname -s may be used to get a short, rather
than fully-qualified, hostname. Some users with symlinked directories
may find `pwd` (backquotes to run the pwd command) gives a more
accurate path than $cwd.

5. Printing the current job name

Often a user will start a long-lived foreground job such as top, an
editor, an email client, etc, and wishes the name of the job to be
shown in the title. This is a more thorny problem and is only achieved
easily in zsh.

5.1. zsh

zsh provides an ideal builtin function for this purpose:

preexec() a function which is just before a command is executed
$*,$1,... arguments passed to preexec()

Thus, we can insert the job name in the title as follows:

case $TERM in
xterm*)
preexec () {
print -Pn "\e]0;$*\a"
}
;;
esac

Note: the preexec() function appeared around version 3.1.2 of zsh, so
you may have to upgrade from an earlier version.

5.2. Other shells

This is not easy in other shells which lack an equivalent of the
preexec() function. If anyone has examples please email them to the
author.

6. Appendix: escapes for other terminal types

Many modern terminals are descended from xterm or rxvt and support the
escape sequences we have used so far. Some proprietary terminals
shipped with various flavours of unix use their own escape sequences.

6.1. IBM aixterm

aixterm recognises the xterm escape sequences.

6.2. SGI wsh , xwsh and winterm

These terminals set $TERM=iris-ansi and use the following escapes:

ESCP1.ystringESC\ Set window title to string

ESCP3.ystringESC\ Set icon title to string

For the full list of xwsh escapes see the xwsh(1G) man page.

The Irix terminals also support the xterm escapes to individually set
window title and icon title, but not the escape to set both.

6.3. Sun cmdtool and shelltool

cmdtool and shelltool both set $TERM=sun-cmd and use the following
escapes:

ESC]lstringESC\ Set window title to string

ESC]LstringESC\ Set icon title to string

These are truly awful programs: use something else.

6.4. CDE dtterm

dtterm sets $TERM=dtterm, and appears to recognise both the standard
xterm escape sequences and the Sun cmdtool sequences (tested on
Solaris 2.5.1, Digital Unix 4.0, HP-UX 10.20).

6.5. HPterm

hpterm sets $TERM=hpterm and uses the following escapes:

ESC&f0klengthDstring Set window title to string of length length

ESC&f-1klengthDstring Set icon title to string of length length

A basic C program to calculate the length and echo the string looks
like this:

#include <string.h>
int main(int argc, char *argv[])
{
printf("\033&f0k%dD%s", strlen(argv[1]), argv[1]);
printf("\033&f-1k%dD%s", strlen(argv[1]), argv[1]);
return(0);
}

We may write a similar shell-script, using the ${#string} (zsh, bash,
ksh) or ${%string} (tcsh) expansion to find the string length. The
following is for zsh:

case $TERM in
hpterm)
str="\e]0;%n@%m: %~\a"
precmd () {print -Pn "\e&f0k${#str}D${str}"}
precmd () {print -Pn "\e&f-1k${#str}D${str}"}
;;
esac

7. Appendix: examples in other languages

It may be useful to write a small program to print an argument to the
title using the xterm escapes. Some examples are provided below.

7.1. C

#include <stdio.h>

int main (int argc, char *argv[]) {
printf("%c]0;%s%c", '\033', argv[1], '\007');
return(0);
}

7.2. Perl

#!/usr/bin/perl
print "\033]0;@ARGV\007";

8. Credits

Thanks to the following people who have provided advice, errata, and
examples for this document.

Paul D. Smith <[email protected]> and Christophe Martin
<[email protected]> both pointed out that I had the quotes the
wrong way round in the bash $PROMPT_COMMAND. Getting them right means
variables are expanded dynamically.

Paul D. Smith <[email protected]> suggested the use of \[...\] in
the bash prompt for embedding non-printing characters.

Christophe Martin <[email protected]> provided the solution for
ksh.

Keith Turner <[email protected]> supplied the escape sequences for Sun
cmdtool and shelltool.

Jean-Albert Ferrez <[email protected]> pointed out some
inconsistencies in the use of "PWD" and "$PWD", and in the use of "\"
vs "\\".

Bob Ellison <[email protected]> and Jim Searle
<[email protected]> tested dtterm on HP-UX.

Teng-Fong Seak <[email protected]> suggested the -s option for
hostname, use of `pwd`, and use of echo under csh.

Trilia <[email protected]> suggested examples in other languages.

Brian Miller <[email protected]> supplied the escape sequences
and examples for hpterm.

Lenny Mastrototaro <[email protected]> explained the Irix terminals'
use of xterm escape sequences.

Paolo Supino <[email protected]> suggested the use of \\$ in the bash
prompt.