  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 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 <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.



