How to change the title of an xterm

Ric Lister, ric@giccs.georgetown.edu

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 several shells, and the appendix gives escape sequences for some other terminal types.

1. Where to find this document
2. Static titles
3. Dynamic titles
4. Examples for different shells
5. Printing the current job name
6. Appendix: escapes for other terminal types
7. Appendix: examples in other languages
8. Credits

1. Where to find this document

This document is now part of the Linux HOWTO Index 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 Truumlmper.

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;_string_BEL -- Set icon name and window title to string
• ESC]1;_string_BEL -- Set icon name to string
• ESC]2;_string_BEL -- 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, which comes with the xterm distribution, or xterm.seq, which comes with the rxvt 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 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 "username@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 prefix 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

1. 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

1. include <stdio.h>

int main (int argc, char *argv[?) {

printf("%c]0;%s%c", '\033', argv[1?, '\007'); return(0);

}

7.2 Perl

1. /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 <psmith@!BayNetworks?.COM> and Christophe Martin <cmartin@ipnl.in2p3.fr> 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 <psmith@!BayNetworks?.COM> suggested the use of \[...\? in the bash prompt for embedding non-printing characters.
  
• Christophe Martin <cmartin@ipnl.in2p3.fr> provided the solution for ksh.
  
• Keith Turner <keith@silvaco.com> supplied the escape sequences for Sun cmdtool and shelltool.
  
• Jean-Albert Ferrez <ferrez@dma.epfl.ch> pointed out some inconsistencies in the use of "PWD" and "$PWD", and in the use of "\" vs "\\".
  
• Bob Ellison <papillo@hpellis.fc.hp.com> and Jim Searle <jims@broadcom.com> tested dtterm on HP-UX.
  
• Teng-Fong Seak <seak@drfc.cad.cea.fr> suggested the -s option for hostname, use of `pwd`, and use of echo under csh.
  
• Trilia <trilia@nmia.com> suggested examples in other languages.
  
• Brian Miller <bmiller@telstra.com.au> supplied the escape sequences and examples for hpterm.
  
• Lenny Mastrototaro <lenny@click3x.com> explained the Irix terminals' use of xterm escape sequences.
  
• Paolo Supino <paolo@init.co.il> suggested the use of \\$ in the bash prompt.