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Bash Prompt HOWTO

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  Bash Prompt HOWTO
  Giles Orr, [email protected]
  v0.76 31 December 1999

  Creating and controlling terminal and xterm prompts is discussed,
  including incorporating standard escape sequences to give username,
  current working directory, time, etc.  Further suggestions are made on
  how to modify xterm title bars, use external functions to provide
  prompt information, and how to use ANSI colours.
  ______________________________________________________________________

  Table of Contents



  1. Introduction and Administrivia

     1.1 Requirements
     1.2 How To Use This Document
     1.3 Translations
     1.4 Problems
     1.5 Send Me Comments and Suggestions
     1.6 Credits
     1.7 Copyright and Disclaimer

  2. Bash and Bash Prompts

     2.1 What is Bash?
     2.2 What Can Tweaking Your Bash Prompt Do For You?
     2.3 Why Bother?
     2.4 The First Step
     2.5 Bash Prompt Escape Sequences
     2.6 Setting the PS? Strings Permanently

  3. Bash Programming and Shell Scripts

     3.1 Variables
     3.2 Quotes and Special Characters
     3.3 Command Substitution
     3.4 Non-Printing Characters in Prompts
     3.5 Sourcing a File
     3.6 Functions, Aliases, and the Environment

  4. External Commands

     4.1 PROMPT_COMMAND
     4.2 External Commands in the Prompt
     4.3 What to Put in Your Prompt

  5. Xterm Title Bar Manipulations

  6. ANSI Escape Sequences: Colours and Cursor Movement

     6.1 Colours
     6.2 Cursor Movement
     6.3 Moving the Cursor With tput

  7. Special Characters: Octal Escape Sequences

  8. The Bash Prompt Package

     8.1 Availability
     8.2 Xterm Fonts
     8.3 Changing the Xterm Font

  9. Loading a Different Prompt

     9.1 Loading a Different Prompt, Later
     9.2 Loading a Different Prompt, Immediately

  10. Loading Prompt Colours Dynamically

     10.1 A "Proof of Concept" Example

  11. Prompt Code Snippets

     11.1 Built-in Escape Sequences
     11.2 Date and Time
     11.3 Counting Files in the Current Directory
     11.4 Total Bytes in the Current Directory
     11.5 Checking the Current TTY
     11.6 Suspended Job Count
     11.7 Uptime and Load
     11.8 Number of Processes
     11.9 Controlling the Width of $PWD
     11.10 Laptop Power
     11.11 Having the Prompt Ignored on Cut and Paste
     11.12 Setting the Window Title and Icon Title Separately

  12. Example Prompts

     12.1 Examples on the Web Over time, many people have e-mailed me excellent examples, and I've written some interesting ones myself.  There are far too many to include here, so I have put all of the examples together into some web pages which can be seen at
     12.2 A "Lightweight" Prompt
     12.3 Elite from Bashprompt Themes
     12.4 A "Power User" Prompt
     12.5 Prompt Depending on Connection Type
     12.6 A Prompt the Width of Your Term
     12.7 The Elegant Useless Clock Prompt


  ______________________________________________________________________

  1.  Introduction and Administrivia

  1.1.  Requirements

  You will need Bash.  The default version for most distributions is
  either 1.14.7, or 2.0.x.  1.14.7 was the standard for years, but is
  slowly being replaced.  I've been using Bash 2.0.x for quite a while
  now, but almost all code presented here should work under 1.14.7.  If
  I'm aware of a problem, I'll mention it.  You can check your Bash
  version by typing echo $BASH_VERSION at the prompt.  On my machine, it
  responds with 2.03.6(1)-release.


  Shell programming experience would be good, but isn't essential: the
  more you know, the more complex the prompts you'll be able to create.
  I assume a basic knowledge of shell programming and Unix utilities as
  I go through this tutorial.  However, my own shell programming skills
  are limited, so I give a lot of examples and explanation that may
  appear unnecessary to an experienced shell programmer.


  1.2.  How To Use This Document

  I include a lot of examples and explanatory text.  Different parts
  will be of varying usefulness to different people.  This has grown
  long enough that reading it straight through would be difficult - just
  read the sections you need, backtrack as necessary.


  1.3.  Translations

  Japanese: http://www.jf.linux.or.jp/JF/JF-ftp/other-formats/Bash-
  Prompt/Bash-Prompt-HOWTO.html, provided by Akira Endo,
  [email protected]


  German: translation is in progress by Thomas Keil, [email protected]
  preissler.de.


  Italian: by Daniel Dui, [email protected], available at
  http://www.crs4.it/~dui/linux.html.



  Portugese: translation is in progress by Mrio Gamito,
  [email protected]



  Spanish: translation by Iosu Santurtn [email protected] at
  http://mipagina.euskaltel.es/iosus/linux/Bash-Prompt-HOWTO.html.


  Dutch: translation is in progress by Ellen Bokhorst [email protected],
  and it will be available at http://www.nl.linux.org/doc/HOWTO.


  Chinese: translation in progress by Allen Huang
  [email protected]  I will include a URL when I have it.


  Many thanks to all of them!  URLs will be included as they're
  available.


  If you are working on a translation, please notify me - especially if
  it's available at a linkable URL.  Thanks.


  1.4.  Problems

  This is a list of problems I've noticed while programming prompts.
  Don't start reading here, and don't let this list discourage you -
  these are mostly quite minor details.  Just check back if you run into
  anything odd.


  o  Many Bash features (such as math within $(()) among others) are
     compile time options.  If you're using a binary distribution such
     as comes with a standard Linux distribution, all such features
     should be compiled in.  But if you're working on someone else's
     system, this is worth keeping in mind if something you expected to
     work doesn't.  Some notes about this in Learning the Bash Shell,
     p.260-262.

  o  The terminal screen manager "screen" doesn't always get along with
     ANSI colours.  I'm not a screen expert, unfortunately.  My current
     version of screen (3.7.6-1, an RPM package) seems to work well in
     all cases, but I've seen occasions where screen reduced all prompt
     colours to the standard foreground colour in X terminals.  This
     doesn't appear to be a problem on the console.

  o  Xdefaults files can override colours.  Look in ~/.Xdefaults for
     lines referring to XTerm*background and XTerm*foreground (or
     possibly XTerm*Background and XTerm*Foreground).

  o  One of the prompts mentioned in this document uses the output of
     "jobs" - as discussed at that time, "jobs" output to a pipe is
     broken in Bash 2.02.

  o  ANSI cursor movement escape sequences aren't all implemented in all
     X terminals.  That's discussed in its own section.

  o  Some nice looking pseudo-graphics can be created by using a VGA
     font rather than standard Linux fonts.  Unfortunately, these
     effects look awful if you don't use a VGA font, and there's no way
     to detect within a term what kind of font it's using.

  o  Bash 2.0+ is out, and it incorporates some new features, and
     changes some behaviour.  Things that work under 1.14.7 don't
     necessarily work the same under 2.0+, or vice versa.


  1.5.  Send Me Comments and Suggestions

  This is a learning experience for me.  I've come to know a fair bit
  about what can be done to create interesting and useful Bash Prompts,
  but I need your input to correct and improve this document.  I've
  tried to check suggestions I make against different versions of Bash
  (2.0x and 1.14.7), but let me know of any incompatibilities you find.


  The latest version of this document should always be available at
  http://www.interlog.com/~giles/bashprompt/.  Please check this out,
  and feel free to e-mail me at [email protected] with suggestions.


  I use the Linux Documentation Project HOWTOs almost exclusively in the
  HTML format, so when I convert this from SGML (its native format),
  HTML is the only format I check thoroughly.  If there are problems
  with other formats, I may not know about them, and I'd appreciate a
  note about them.


  1.6.  Credits

  In producing this document, I have borrowed heavily from the work of
  the Bashprompt project at http://bash.current.nu/.  Other sources used
  include the xterm Title mini-HOWTO by Ric Lister, available at
  http://sunsite.unc.edu/LDP/HOWTO/mini/Xterm-Title.html, Ansi Prompts
  by Keebler, available at http://www.ncal.verio.com/~keebler/ansi.html,
  How to make a Bash Prompt Theme by Stephen Webb, available at
  http://bash.current.nu/bash/HOWTO.html, and X ANSI Fonts by Stumpy,
  available at http://home.earthlink.net/~us5zahns/enl/ansifont.html.


  Also of immense help were several conversations and e-mails from Dan,
  an ex-co-worker at Georgia College & State University, whose knowledge
  of Unix far exceeds mine.  He's given me several excellent
  suggestions, and ideas of his have led to some interesting prompts.


  Three books that have been very useful while programming prompts are
  Linux in a Nutshell by Jessica Heckman Perry (O'Reilly, 1997),
  Learning the Bash Shell by Cameron Newham and Bill Rosenblatt
  (O'Reilly, 2nd. ed., 1998) and Unix Shell Programming by Lowell Jay
  Arthur (Wiley, 1986.  This is the first edition, the fourth came out
  in 1997).


  1.7.  Copyright and Disclaimer

  This document is copyright 1998-1999 by Giles Orr.  You are encouraged
  to redistribute it.  You may not modify this document (see the section
  on contacting me: I incorporate most changes recommended by readers).
  Please contact me if you're interested in doing a translation.


  This document is available for free, and, while I have done the best I
  can to make it accurate and up to date, I take no responsibility for
  any problems you may encounter resulting from the use of this
  document.



  2.  Bash and Bash Prompts

  2.1.  What is Bash?

  Descended from the Bourne Shell, Bash is a GNU product, the "Bourne
  Again SHell."  It's the standard command line interface on most Linux
  machines.  It excels at interactivity, supporting command line
  editing, completion, and recall.  It also supports configurable
  prompts - most people realize this, but don't know how much can be
  done.


  2.2.  What Can Tweaking Your Bash Prompt Do For You?

  Most Linux systems have a default prompt in one colour (usually gray)
  that tells you your user name, the name of the machine you're working
  on, and some indication of your current working directory.  This is
  all useful information, but you can do much more with the prompt: all
  sorts of information can be displayed (tty number, time, date, load,
  number of users, uptime ...) and the prompt can use ANSI colours,
  either to make it look interesting, or to make certain information
  stand out.  You can also manipulate the title bar of an Xterm to
  reflect some of this information.


  2.3.  Why Bother?

  Beyond looking cool, it's often useful to keep track of system
  information.  One idea that I know appeals to some people is that it
  makes it possible to put prompts on different machines in different
  colours.  If you have several Xterms open on several different
  machines, or if you tend to forget what machine you're working on and
  delete the wrong files (or shut down the server instead of the
  workstation), you'll find this a great way to remember what machine
  you're on.


  For myself, I like the utility of having information about my machine
  and work environment available all the time.  And I like the challenge
  of trying to figure out how to put the maximum amount of information
  into the smallest possible space while maintaining readability.



  2.4.  The First Step

  The appearance of the prompt is governed by the shell variable PS1.
  Command continuations are indicated by the PS2 string, which can be
  modified in exactly the same ways discussed here - since controlling
  it is exactly the same, and it isn't as "interesting," I'll mostly be
  modifying the PS1 string.  (There are also PS3 and PS4 strings.  These
  are never seen by the average user - see the Bash man page if you're
  interested in their purpose.)  To change the way the prompt looks, you
  change the PS1 variable.  For experimentation purposes, you can enter
  the PS1 strings directly at the prompt, and see the results
  immediately (this only affects your current session, and the changes
  go away when you log out).  If you want to make a change to the prompt
  permanent, look at the section below ``Setting the PS? Strings
  Permanently''.


  Before we get started, it's important to remember that the PS1 string
  is stored in the environment like any other environment variable.  If
  you modify it at the command line, your prompt will change.  Before
  you make any changes, you can save your current prompt to another
  environment variable:
       [[email protected] giles]$ SAVE=$PS1
       [[email protected] giles]$



  The simplest prompt would be a single character, such as:



       [[email protected] giles]$ PS1=$
       $ls
       bin   mail
       $



  This demonstrates the best way to experiment with basic prompts,
  entering them at the command line.  Notice that the text entered by
  the user appears immediately after the prompt: I prefer to use



       $PS1="$ "
       $ ls
       bin   mail
       $



  which forces a space after the prompt, making it more readable.  To
  restore your original prompt, just call up the variable you stored:



       $ PS1=$SAVE
       [[email protected] giles]$



  2.5.  Bash Prompt Escape Sequences

  There are a lot of escape sequences offered by the Bash shell for
  insertion in the prompt.  From the Bash 2.02 man page:



  When executing interactively, bash  displays  the  primary
  prompt  PS1  when  it  is ready to read a command, and the
  secondary prompt PS2 when it needs more input to  complete
  a  command.   Bash  allows these prompt strings to be cus-
  tomized by inserting a number of backslash-escaped special
  characters that are decoded as follows:
         \a     an ASCII bell character (07)
         \d     the  date  in  "Weekday  Month  Date" format
                (e.g., "Tue May 26")
         \e     an ASCII escape character (033)
         \h     the hostname up to the first `.'
         \H     the hostname
         \n     newline
         \r     carriage return
         \s     the name of the shell, the  basename  of  $0
                (the portion following the final slash)
         \t     the current time in 24-hour HH:MM:SS format
         \T     the current time in 12-hour HH:MM:SS format
         \@     the current time in 12-hour am/pm format
         \u     the username of the current user
         \v     the version of bash (e.g., 2.00)
         \V     the  release  of  bash, version + patchlevel
                (e.g., 2.00.0)
         \w     the current working directory
         \W     the basename of the current  working  direc-
                tory
         \!     the history number of this command
         \#     the command number of this command
         \$     if  the effective UID is 0, a #, otherwise a
                $
         \nnn   the character  corresponding  to  the  octal
                number nnn
         \\     a backslash
         \[     begin a sequence of non-printing characters,
                which could be used to embed a terminal con-
                trol sequence into the prompt
         \]     end a sequence of non-printing characters



  Continuing where we left off:



       [[email protected] giles]$ PS1="\[email protected]\h \W> "
       [email protected] giles> ls
       bin   mail
       [email protected] giles>



  This is similar to the default on most Linux distributions.  I wanted
  a slightly different appearance, so I changed this to:



       [email protected] giles> PS1="[\t][\[email protected]\h:\w]\$ "
       [21:52:01][[email protected]:~]$ ls
       bin   mail
       [21:52:15][[email protected]:~]$


  2.6.  Setting the PS? Strings Permanently

  Various people and distributions set their PS? strings in different
  places.  The most common places are /etc/profile, /etc/bashrc,
  ~/.bash_profile, and ~/.bashrc .  Johan Kullstam ([email protected])
  writes:



       the PS1 string should be set in .bashrc.  this is because
       non-interactive bashes go out of their way to unset PS1.
       the bash man page tells how the presence or absence of PS1
       is a good way of knowing whether one is in an interactive vs
       non-interactive (ie script) bash session.


       the way i realized this is that startx is a bash script.
       what this means is, startx will wipe out your prompt.  when
       you set PS1 in .profile (or .bash_profile), login at
       console, fire up X via startx, your PS1 gets nuked in the
       process leaving you with the default prompt.


       one workaround is to launch xterms and rxvts with the -ls
       option to force them to read .profile.  but any time a shell
       is called via a non-interactive shell-script middleman PS1
       is lost.  system(3) uses sh -c which if sh is bash will kill
       PS1.  a better way is to place the PS1 definition in
       .bashrc.  this is read every time bash starts and is where
       interactive things - eg PS1 should go.


       therefore it should be stressed that PS1=..blah.. should be
       in .bashrc and not .profile.



  I tried to duplicate the problem he explains, and encountered a
  different one: my PROMPT_COMMAND variable (which will be introduced
  later) was blown away.  My knowledge in this area is somewhat shaky,
  so I'm going to go with what Johan says.



  3.  Bash Programming and Shell Scripts

  3.1.  Variables

  I'm not going to try to explain all the details of Bash scripting in a
  section of this HOWTO, just the details pertaining to prompts.  If you
  want to know more about shell programming and Bash in general, I
  highly recommend Learning the Bash Shell by Cameron Newham and Bill
  Rosenblatt (O'Reilly, 1998).  Oddly, my copy of this book is quite
  frayed.  Again, I'm going to assume that you know a fair bit about
  Bash already.  You can skip this section if you're only looking for
  the basics, but remember it and refer back if you proceed much
  farther.


  Variables in Bash are assigned much as they are in any programming
  language:



  testvar=5
  foo=zen
  bar="bash prompt"



  Quotes are only needed in an assignment if a space (or special
  character, discussed shortly) is a part of the variable.


  Variables are referenced slightly differently than they are assigned:



       > echo $testvar
       5
       > echo $foo
       zen
       > echo ${bar}
       bash prompt
       > echo $NotAssigned

       >



  A variable can be referred to as $bar or ${bar}.  The braces are
  useful when it is unclear what is being referenced: if I write $barley
  do I mean ${bar}ley or ${barley}?  Note also that referencing a value
  that hasn't been assigned doesn't generate an error, instead returning
  nothing.


  3.2.  Quotes and Special Characters

  If you wish to include a special character in a variable, you will
  have to quote it differently:



       > newvar=$testvar
       > echo $newvar
       5
       > newvar="$testvar"
       > echo $newvar
       5
       > newvar='$testvar'
       > echo $newvar
       $testvar
       > newvar=\$testvar
       > echo $newvar
       $testvar
       >



  The dollar sign isn't the only character that's special to the Bash
  shell, but it's a simple example.  An interesting step we can take to
  make use of assigning a variable name to another variable name is to
  use eval to dereference the stored variable name:



  > echo $testvar
  5
  > echo $newvar
  $testvar
  > eval echo $newvar
  5
  >



  Normally, the shell does only one round of substitutions on the
  expression it is evaluating: if you say echo $newvar the shell will
  only go so far as to determine that $newvar is equal to the text
  string $testvar, it won't evaluate what $testvar is equal to.  eval
  forces that evaluation.


  3.3.  Command Substitution

  In almost all cases in this document, I use the $(<command>)
  convention for command substitution: that is,



       $(date +%H%M)



  means "substitute the output from the date +%H%M command here." This
  works in Bash 2.0+.  In some older versions of Bash, prior to 1.14.7,
  you may need to use backquotes (`date +%H%M`).  Backquotes can be used
  in Bash 2.0+, but are being phased out in favor of $(), which nests
  better.  If you're using an earlier version of Bash, you can usually
  substitute backquotes where you see $().  If the command substitution
  is escaped (ie.  \$(command) ), then use backslashes to escape BOTH
  your backquotes (ie.  \'command\' ).


  3.4.  Non-Printing Characters in Prompts

  Many of the changes that can be made to Bash prompts that are
  discussed in this HOWTO use non-printing characters.  Changing the
  colour of the prompt text, changing an Xterm title bar, and moving the
  cursor position all require non-printing characters.


  If I want a very simple prompt consisting of a greater-than sign and a
  space:



       [[email protected] giles]$ PS1='> '
       >



  This is just a two character prompt.  If I modify it so that it's a
  bright yellow greater-than sign (colours are discussed in their own
  section):



  > PS1='\033[1;33m>\033[0m '
  >



  This works fine - until you type in a large command line.  Because the
  prompt still only consists of two printing characters (a greater-than
  sign and a space) but the shell thinks that this prompt is eleven
  characters long (I think it counts '\033' , '[1' and '[0' as one
  character each).  You can see this by typing a really long command
  line - you will find that the shell wraps the text before it gets to
  the edge of the terminal, and in most cases wraps it badly.  This is
  because it's confused about the actual length of the prompt.


  So use this instead:



       > PS1='\[\033[1;33m\]>\[\033[0m\] '



  This is more complex, but it works.  Command lines wrap properly.
  What's been done is to enclose the '\033[1;33m' that starts the yellow
  colour in square brackets, including the brackets themselves, is a
  non-printing character."  The same is done with the '\033[0m' that
  ends the colour.


  3.5.  Sourcing a File

  When a file is sourced (by typing either source filename or .
  filename at the command line), the lines of code in the file are
  executed as if they were printed at the command line.  This is
  particularly useful with complex prompts, to allow them to be stored
  in files and called up by sourcing the file they are in.


  In examples, you will find that I often include #!/bin/bash at the
  beginning of files including functions.  This is not necessary if you
  are sourcing a file, just as it isn't necessary to chmod +x a file
  that is going to be sourced.  I do this because it makes Vim (my
  editor of choice, no flames please - you use what you like) think I'm
  editing a shell script and turn on colour syntax highlighting.


  3.6.  Functions, Aliases, and the Environment

  As mentioned earlier, PS1, PS2, PS3, PS4, and PROMPT_COMMAND are all
  stored in the Bash environment.  For those of us coming from a DOS
  background, the idea of tossing big hunks of code into the environment
  is horrifying, because that DOS environment was small, and didn't
  exactly grow well.  There are probably practical limits to what you
  can and should put in the environment, but I don't know what they are,
  and we're probably talking a couple of orders of magnitude larger than
  what DOS users are used to.  As Dan put it:


  "In my interactive shell I have 62 aliases and 25 functions.  My rule
  of thumb is that if I need something solely for interactive use and
  can handily write it in bash I make it a shell function (assuming it
  can't be easily expressed as an alias).  If these people are worried
  about memory they don't need to be using bash.  Bash is one of the
  largest programs I run on my linux box (outside of Oracle).  Run top
  sometime and press 'M' to sort by memory - see how close bash is to
  the top of the list.  Heck, it's bigger than sendmail!  Tell 'em to go
  get ash or something."


  I guess he was using console only the day he tried that: running X and
  X apps, I have a lot of stuff larger than Bash.  But the idea is the
  same: the environment is something to be used, and don't worry about
  overfilling it.


  I risk censure by Unix gurus when I say this (for the crime of over-
  simplification), but functions are basically small shell scripts that
  are loaded into the environment for the purpose of efficiency.
  Quoting Dan again: "Shell functions are about as efficient as they can
  be.  It is the approximate equivalent of sourcing a bash/bourne shell
  script save that no file I/O need be done as the function is already
  in memory.  The shell functions are typically loaded from [.bashrc or
  .bash_profile] depending on whether you want them only in the initial
  shell or in subshells as well.  Contrast this with running a shell
  script: Your shell forks, the child does an exec, potentially the path
  is searched, the kernel opens the file and examines enough bytes to
  determine how to run the file, in the case of a shell script a shell
  must be started with the name of the script as its argument, the shell
  then opens the file, reads it and executes the statements.  Compared
  to a shell function, everything other than executing the statements
  can be considered unnecessary overhead."


  Aliases are simple to create:



       alias d="ls --color=tty --classify"
       alias v="d --format=long"
       alias rm="rm -i"



  Any arguments you pass to the alias are passed to the command line of
  the aliased command (ls in the first two cases).  Note that aliases
  can be nested, and they can be used to make a normal unix command
  behave in a different way.  (I agree with the argument that you
  shouldn't use the latter kind of aliases - if you get in the habit of
  relying on "rm *" to ask you if you're sure, you may lose important
  files on a system that doesn't use your alias.)


  Functions are used for more complex program structures.  As a general
  rule, use an alias for anything that can be done in one line.
  Functions differ from shell scripts in that they are loaded into the
  environment so that they work more quickly.  As a general rule again,
  you would want to keep functions relatively small, and any shell
  script that gets relatively large should remain a shell script rather
  than turning it into a function.  Your decision to load something as a
  function is also going to depend on how often you use it.  If you use
  a small shell script infrequently, leave it as a shell script.  If you
  use it often, turn it into a function.


  To modify the behaviour of ls, you could do something like the
  following:


       function lf
       {
           ls --color=tty --classify $*
           echo "$(ls -l $* | wc -l) files"
       }



  This could readily be set as an alias, but for the sake of example,
  we'll make it a function.  If you type the text shown into a text file
  and then source that file, the function will be in your environment,
  and be immediately available at the command line without the overhead
  of a shell script mentioned previously.  The usefulness of this
  becomes more obvious if you consider adding more functionality to the
  above function, such as using an if statement to execute some special
  code when links are found in the listing.



  4.  External Commands

  4.1.  PROMPT_COMMAND

  Bash provides another environment variable called PROMPT_COMMAND.  The
  contents of this variable are executed as a regular Bash command just
  before Bash displays a prompt.



       [21:55:01][[email protected]:~] PS1="[\[email protected]\h:\w]\$ "
       [[email protected]:~] PROMPT_COMMAND="date +%H%M"
       2155
       [[email protected]:~] d
       bin   mail
       2156
       [[email protected]:~]



  What happened above was that I changed PS1 to no longer include the \t
  escape sequence, so the time was no longer a part of the prompt.  Then
  I used date +%H%M to display the time in a format I like better.  But
  it appears on a different line than the prompt.  Tidying this up using
  echo -n ... as shown below works with Bash 2.0+, but appears not to
  work with Bash 1.14.7: apparently the prompt is drawn in a different
  way, and the following method results in overlapping text.



       2156
       [[email protected]:~] PROMPT_COMMAND="echo -n [$(date +%H%M)]"
       [2156][[email protected]:~]$
       [2156][[email protected]:~]$ d
       bin   mail
       [2157][[email protected]:~]$ unset PROMPT_COMMAND
       [[email protected]:~]



  echo -n ... controls the output of the date command and supresses the
  trailing newline, allowing the prompt to appear all on one line.  At
  the end, I used the unset command to remove the PROMPT_COMMAND
  environment variable.



  4.2.  External Commands in the Prompt

  You can use the output of regular Linux commands directly in the
  prompt as well.  Obviously, you don't want to insert a lot of
  material, or it will create a large prompt.  You also want to use a
  fast command, because it's going to be executed every time your prompt
  appears on the screen, and delays in the appearance of your prompt
  while you're working can be very annoying.  (Unlike the previous
  example that this closely resembles, this does work with Bash 1.14.7.)



       [21:58:33][[email protected]:~]$ PS1="[\$(date +%H%M)][\[email protected]\h:\w]\$ "
       [2159][[email protected]:~]$ ls
       bin   mail
       [2200][[email protected]:~]$



  It's important to notice the backslash before the dollar sign of the
  command substitution.  Without it, the external command is executed
  exactly once: when the PS1 string is read into the environment.  For
  this prompt, that would mean that it would display the same time no
  matter how long the prompt was used.  The backslash protects the
  contents of $() from immediate shell interpretation, so "date" is
  called every time a prompt is generated.


  Linux comes with a lot of small utility programs like date, grep, or
  wc that allow you to manipulate data.  If you find yourself trying to
  create complex combinations of these programs within a prompt, it may
  be easier to make an alias, function, or shell script of your own, and
  call it from the prompt.  Escape sequences are often required in bash
  shell scripts to ensure that shell variables are expanded at the
  correct time (as seen above with the date command): this is raised to
  another level within the prompt PS1 line, and avoiding it by creating
  functions is a good idea.


  An example of a small shell script used within a prompt is given
  below:


  ______________________________________________________________________
  #!/bin/bash
  #     lsbytesum - sum the number of bytes in a directory listing
  TotalBytes=0
  for Bytes in $(ls -l | grep "^-" | cut -c30-41)
  do
      let TotalBytes=$TotalBytes+$Bytes
  done
  TotalMeg=$(echo -e "scale=3 \n$TotalBytes/1048576 \nquit" | bc)
  echo -n "$TotalMeg"
  ______________________________________________________________________



  I have at times kept this both as a function, or as a shell script in
  my ~/bin directory, which is on my path.  Used in a prompt:



       [2158][[email protected]:~]$ PS1="[\[email protected]\h:\w (\$(lsbytesum) Mb)]\$ "
       [[email protected]:~ (0 Mb)]$ cd /bin
       [[email protected]:/bin (4.498 Mb)]$



  4.3.  What to Put in Your Prompt

  You'll find I put username, machine name, time, and current directory
  name in most of my prompts.  With the exception of the time, these are
  very standard items to find in a prompt, and time is probably the next
  most common addition.  But what you include is entirely a matter of
  personal taste.  Here are examples from people I know to help give you
  ideas.


  Dan's prompt is minimal but very effective, particularly for the way
  he works.



       [[email protected]:~]$ cur_tty=$(tty | sed -e "s/.*tty\(.*\)/\1/")
       [[email protected]:~]$ echo $cur_tty
       p4
       [[email protected]:~]$ PS1="\!,$cur_tty,\$?\$ "
       1095,p4,0$



  Dan doesn't like that having the current working directory can resize
  the prompt drastically as you move through the directory tree, so he
  keeps track of that in his head (or types "pwd").  He learned Unix
  with csh and tcsh, so he uses his command history extensively
  (something many of us weened on Bash do not do), so the first item in
  the prompt is the history number.  The second item is the significant
  characters of the tty (the output of "tty" is cropped with sed), an
  item that can be useful to "screen" users.  The third item is the exit
  value of the last command/pipeline (note that this is rendered useless
  by any command executed within the prompt - you could work around that
  by capturing it to a variable and playing it back, though).  Finally,
  the "\$" is a dollar sign for a regular user, and switches to a hash
  mark ("#") if the user is root.


  Torben Fjerdingstad ([email protected]) wrote to tell me that he
  often suspends jobs and then forgets about them.  He uses his prompt
  to remind himself of suspended jobs:



  [[email protected]:~]$ function jobcount {
  > jobs|wc -l| awk '{print $1}'
  > }
  [[email protected]:~]$ export PS1='\W[`jobcount`]# '
  giles[0]# man ls &
  [1] 4150

  [1]+  Stopped (tty output)    man ls
  giles[1]#



  Torben uses awk to trim the whitespace from the output of wc, while I
  would have used sed or tr - not because they're better, but because
  I'm more familiar with them.  There are probably other ways as well.
  Torben also surrounds his PS1 string in single quotes, which prevent
  Bash from immediately interpreting the backquotes, so he doesn't have
  to escape them as I have mentioned.


  NOTE: There is a known bug in Bash 2.02 that causes the jobs command
  (a shell builtin) to return nothing to a pipe.  If you try the above
  under Bash 2.02, you will always get a "0" back regardless of how many
  jobs you have suspended.  This problem is fixed in 2.03.



  5.  Xterm Title Bar Manipulations

  Non-printing escape sequences can be used to produce interesting
  effects in prompts.  To use these escape sequences, you need to
  enclose them in \[ and \] (as discussed in ``Non-Printing Characters
  in Prompts''), telling Bash to ignore this material while calculating
  the size of the prompt.  Failing to include these delimiters results
  in line editing code placing the cursor incorrectly because it doesn't
  know the actual size of the prompt.  Escape sequences must also be
  preceded by \033[ in Bash prior to version 2, or by either \033[ or
  \e[ in later versions.


  If you try to change the title bar of your Xterm with your prompt when
  you're at the console, you'll produce garbage in your prompt.  To
  avoid this, test the TERM environment variable to tell if your prompt
  is going to be in an Xterm.



  ______________________________________________________________________
  function proml
  {
  case $TERM in
      xterm*)
          local TITLEBAR='\[\033]0;\[email protected]\h:\w\007\]'
          ;;
      *)
          local TITLEBAR=''
          ;;
  esac

  PS1="${TITLEBAR}\
  [\$(date +%H%M)]\
  [\[email protected]\h:\w]\
  \$ "
  PS2='> '
  PS4='+ '
  }
  ______________________________________________________________________



  This is a function that can be incorporated into ~/.bashrc.  The
  function name could then be called to execute the function.  The
  function, like the PS1 string, is stored in the environment.  Once the
  PS1 string is set by the function, you can remove the function from
  the environment with unset proml.  Since the prompt can't change from
  being in an Xterm to being at the console, the TERM variable isn't
  tested every time the prompt is generated.  I used continuation
  markers (backslashes) in the definition of the prompt, to allow it to
  be continued on multiple lines.  This improves readability, making it
  easier to modify and debug.


  I define this as a function because this is how the Bashprompt package
  (discussed later in this document: ``The Bash Prompt Package'') deals
  with prompts: it's not the only way to do it, but it works well.  As
  the prompts you use become more complex, it becomes more and more
  cumbersome to type them in at the prompt, and more practical to make
  them into some sort of text file.  In this case, to test this at the
  prompt, save the above as a text file called "proml".  You can work
  with it as follows:



       [[email protected]:/bin (4.498 Mb)]$ cd          -> Go where you want to save the prompt
       [[email protected]:~ (0 Mb)]$ vi proml           -> Edit the prompt file
       ...                                         -> Enter the text given above
       [[email protected]:~ (0 Mb)]$ source proml       -> Read the prompt function
       [[email protected]:~ (0 Mb)]$ proml              -> Execute the prompt function



  The first step in creating this prompt is to test if the shell we're
  starting is an xterm or not: if it is, the shell variable
  (${TITLEBAR}) is defined.  It consists of the appropriate escape
  sequences, and \[email protected]\h:\w, which puts <user>@<machine>:<working
  directory> in the Xterm title bar.  This is particularly useful with
  minimized Xterms, making them more rapidly identifiable.  The other
  material in this prompt should be familiar from previous prompts we've
  created.

  The only drawback to manipulating the Xterm title bar like this occurs
  when you log into a system on which you haven't set up the title bar
  hack: the Xterm will continue to show the information from the
  previous system that had the title bar hack in place.



  6.  ANSI Escape Sequences: Colours and Cursor Movement

  6.1.  Colours

  As mentioned before, non-printing escape sequences have to be enclosed
  in \[\033[ and \].  For colour escape sequences, they should also be
  followed by a lowercase m.


  If you try out the following prompts in an xterm and find that you
  aren't seeing the colours named, check out your ~/.Xdefaults file (and
  possibly its bretheren) for lines like "XTerm*Foreground:
  BlanchedAlmond".  This can be commented out by placing an exclamation
  mark ("!") in front of it.  Of course, this will also be dependent on
  what terminal emulator you're using.  This is the likeliest place that
  your term foreground colours would be overridden.


  To include blue text in the prompt:



       PS1="\[\033[34m\][\$(date +%H%M)][\[email protected]\h:\w]$ "



  The problem with this prompt is that the blue colour that starts with
  the 34 colour code is never switched back to the regular colour, so
  any text you type after the prompt is still in the colour of the
  prompt.  This is also a dark shade of blue, so combining it with the
  bold code might help:



       PS1="\[\033[1;34m\][\$(date +%H%M)][\[email protected]\h:\w]$\[\033[0m\] "



  The prompt is now in light blue, and it ends by switching the colour
  back to nothing (whatever foreground colour you had previously).


  Here are the rest of the colour equivalences:



       Black       0;30     Dark Gray     1;30
       Blue        0;34     Light Blue    1;34
       Green       0;32     Light Green   1;32
       Cyan        0;36     Light Cyan    1;36
       Red         0;31     Light Red     1;31
       Purple      0;35     Light Purple  1;35
       Brown       0;33     Yellow        1;33
       Light Gray  0;37     White         1;37

  Daniel Dui ([email protected]) points out that to be strictly accurate, we
  must mention that the list above is for colours at the console.  In an
  xterm, the code 1;31 isn't "Light Red," but "Bold Red."  This is true
  of all the colours.


  You can also set background colours by using 44 for Blue background,
  41 for a Red background, etc.  There are no bold background colours.
  Combinations can be used, like Light Red text on a Blue background:
  \[\033[44;1;31m\], although setting the colours separately seems to
  work better (ie. \[\033[44m\]\[\033[1;31m\]).  Other codes available
  include 4: Underscore, 5: Blink, 7: Inverse, and 8: Concealed.


  Aside: Many people (myself included) object strongly to the "blink"
  attribute.  Fortunately, it doesn't work in any terminal emulators
  that I'm aware of - but it will still work on the console.  And, if
  you were wondering (as I did) "What use is a 'Concealed' attribute?!"
  - I saw it used in an example shell script (not a prompt) to allow
  someone to type in a password without it being echoed to the screen.


  Based on a prompt called "elite2" in the Bashprompt package (which I
  have modified to work better on a standard console, rather than with
  the special xterm fonts required to view the original properly), this
  is a prompt I've used a lot:


  ______________________________________________________________________

  function elite
  {

  local GRAY="\[\033[1;30m\]"
  local LIGHT_GRAY="\[\033[0;37m\]"
  local CYAN="\[\033[0;36m\]"
  local LIGHT_CYAN="\[\033[1;36m\]"

  case $TERM in
      xterm*)
          local TITLEBAR='\[\033]0;\[email protected]\h:\w\007\]'
          ;;
      *)
          local TITLEBAR=""
          ;;
  esac

  local GRAD1=$(tty|cut -d/ -f3)
  PS1="$TITLEBAR\
  $GRAY-$CYAN-$LIGHT_CYAN(\
  $CYAN\[email protected]$CYAN\h\
  $LIGHT_CYAN)$CYAN-$LIGHT_CYAN(\
  $CYAN\#$GRAY/$CYAN$GRAD1\
  $LIGHT_CYAN)$CYAN-$LIGHT_CYAN(\
  $CYAN\$(date +%H%M)$GRAY/$CYAN\$(date +%d-%b-%y)\
  $LIGHT_CYAN)$CYAN-$GRAY-\
  $LIGHT_GRAY\n\
  $GRAY-$CYAN-$LIGHT_CYAN(\
  $CYAN\$$GRAY:$CYAN\w\
  $LIGHT_CYAN)$CYAN-$GRAY-$LIGHT_GRAY "
  PS2="$LIGHT_CYAN-$CYAN-$GRAY-$LIGHT_GRAY "
  }
  ______________________________________________________________________



  I define the colours as temporary shell variables in the name of
  readability.  It's easier to work with.  The "GRAD1" variable is a
  check to determine what terminal you're on.  Like the test to
  determine if you're working in an Xterm, it only needs to be done
  once.  The prompt you see look like this, except in colour:



       --([email protected])-(75/ttyp7)-(1908/12-Oct-98)--
       --($:~/tmp)--



  To help myself remember what colours are available, I wrote the
  following script which echoes all the colours to screen:



  ______________________________________________________________________
  #!/bin/bash
  #
  #   This file echoes a bunch of colour codes to the terminal to demonstrate
  #   what's available.  Each line is one colour on black and gray
  #   backgrounds, with the code in the middle.  Verified to work on white,
  #   black, and green BGs (2 Dec 98).
  #
  echo "  On Light Gray:        On Black:"
  echo -e "\033[47m\033[1;37m  White        \033[0m\
   1;37m \
  \033[40m\033[1;37m  White        \033[0m"
  echo -e "\033[47m\033[37m  Light Gray   \033[0m\
     37m \
  \033[40m\033[37m  Light Gray   \033[0m"
  echo -e "\033[47m\033[1;30m  Gray         \033[0m\
   1;30m \
  \033[40m\033[1;30m  Gray         \033[0m"
  echo -e "\033[47m\033[30m  Black        \033[0m\
     30m \
  \033[40m\033[30m  Black        \033[0m"
  echo -e "\033[47m\033[31m  Red          \033[0m\
     31m \
  \033[40m\033[31m  Red          \033[0m"
  echo -e "\033[47m\033[1;31m  Light Red    \033[0m\
   1;31m \
  \033[40m\033[1;31m  Light Red    \033[0m"
  echo -e "\033[47m\033[32m  Green        \033[0m\
     32m \
  \033[40m\033[32m  Green        \033[0m"
  echo -e "\033[47m\033[1;32m  Light Green  \033[0m\
   1;32m \
  \033[40m\033[1;32m  Light Green  \033[0m"
  echo -e "\033[47m\033[33m  Brown        \033[0m\
     33m \
  \033[40m\033[33m  Brown        \033[0m"
  echo -e "\033[47m\033[1;33m  Yellow       \033[0m\
   1;33m \
  \033[40m\033[1;33m  Yellow       \033[0m"
  echo -e "\033[47m\033[34m  Blue         \033[0m\
     34m \
  \033[40m\033[34m  Blue         \033[0m"
  echo -e "\033[47m\033[1;34m  Light Blue   \033[0m\
   1;34m \
  \033[40m\033[1;34m  Light Blue   \033[0m"
  echo -e "\033[47m\033[35m  Purple       \033[0m\
     35m \
  \033[40m\033[35m  Purple       \033[0m"
  echo -e "\033[47m\033[1;35m  Pink         \033[0m\
   1;35m \
  \033[40m\033[1;35m  Pink         \033[0m"
  echo -e "\033[47m\033[36m  Cyan         \033[0m\
     36m \
  \033[40m\033[36m  Cyan         \033[0m"
  echo -e "\033[47m\033[1;36m  Light Cyan   \033[0m\
   1;36m \
  \033[40m\033[1;36m  Light Cyan   \033[0m"
  ______________________________________________________________________



  6.2.  Cursor Movement

  ANSI escape sequences allow you to move the cursor around the screen
  at will.  This is more useful for full screen user interfaces
  generated by shell scripts, but can also be used in prompts.  The
  movement escape sequences are as follows:



       - Position the Cursor:
         \033[<L>;<C>H
            Or
         \033[<L>;<C>f
         puts the cursor at line L and column C.
       - Move the cursor up N lines:
         \033[<N>A
       - Move the cursor down N lines:
         \033[<N>B
       - Move the cursor forward N columns:
         \033[<N>C
       - Move the cursor backward N columns:
         \033[<N>D

       - Clear the screen, move to (0,0):
         \033[2J
       - Erase to end of line:
         \033[K

       - Save cursor position:
         \033[s
       - Restore cursor position:
         \033[u



  The latter two codes are NOT honoured by many terminal emulators.  The
  only ones that I'm aware of that do are xterm and nxterm - even though
  the majority of terminal emulators are based on xterm code.  As far as
  I can tell, rxvt, kvt, xiterm, and Eterm do not support them.  They
  are supported on the console.


  Try putting in the following line of code at the prompt (it's a little
  clearer what it does if the prompt is several lines down the terminal
  when you put this in): echo -en "\033[7A\033[1;35m BASH
  \033[7B\033[6D" This should move the cursor seven lines up screen,
  print the word " BASH ", and then return to where it started to
  produce a normal prompt.  This isn't a prompt: it's just a
  demonstration of moving the cursor on screen, using colour to
  emphasize what has been done.


  Save this in a file called "clock":



  ______________________________________________________________________
  #!/bin/bash

  function prompt_command {
  let prompt_x=$COLUMNS-5
  }

  PROMPT_COMMAND=prompt_command

  function clock {
  local       BLUE="\[\033[0;34m\]"
  local        RED="\[\033[0;31m\]"
  local  LIGHT_RED="\[\033[1;31m\]"
  local      WHITE="\[\033[1;37m\]"
  local  NO_COLOUR="\[\033[0m\]"
  case $TERM in
      xterm*)
          TITLEBAR='\[\033]0;\[email protected]\h:\w\007\]'
          ;;
      *)
          TITLEBAR=""
          ;;
  esac

  PS1="${TITLEBAR}\
  \[\033[s\033[1;\$(echo -n \${prompt_x})H\]\
  $BLUE[$LIGHT_RED\$(date +%H%M)$BLUE]\[\033[u\033[1A\]
  $BLUE[$LIGHT_RED\[email protected]\h:\w$BLUE]\
  $WHITE\$$NO_COLOUR "
  PS2='> '
  PS4='+ '
  }
  ______________________________________________________________________



  This prompt is fairly plain, except that it keeps a 24 hour clock in
  the upper right corner of the terminal (even if the terminal is
  resized).  This will NOT work on the terminal emulators that I
  mentioned that don't accept the save and restore cursor position
  codes.  If you try to run this prompt in any of those terminal
  emulators, the clock will appear correctly, but the prompt will be
  trapped on the second line of the terminal.


  See also ``The Elegant Useless Clock Prompt'' for a more extensive use
  of these codes.


  6.3.  Moving the Cursor With tput

  As with so many things in Unix, there is more than one way to achieve
  the same ends.  A utility called "tput" can also be used to move the
  cursor around the screen, or get back information about the status of
  the terminal.  "tput" for cursor positioning is less flexible than
  ANSI escape sequences: you can only move the cursor to an absolute
  position, you can't move it relative to its current position.  I don't
  use "tput," so I'm not going to explain it in detail.  Type "man tput"
  and you'll know as much as I do.



  7.  Special Characters: Octal Escape Sequences

  Outside of the characters that you can type on your keyboard, there
  are a lot of other characters you can print on your screen.  I've
  created a script to allow you to check out what the font you're using
  has available for you.  The main command you need to use to utilise
  these characters is "echo -e".  The "-e" switch tells echo to enable
  interpretation of backslash-escaped characters.  What you see when you
  look at octal 200-400 will be very different with a VGA font from what
  you will see with a standard Linux font.  Be warned that some of these
  escape sequences have odd effects on your terminal, and I haven't
  tried to prevent them from doing whatever they do.  The linedraw and
  block characters (which many of us became familiar with with Word
  Perfect) that are used heavily by the Bashprompt project are between
  octal 260 and 337.



  ______________________________________________________________________
  #!/bin/bash

  #   Script: escgen

  function usage {
     echo -e "\033[1;34mescgen\033[0m <lower_octal_value> [<higher_octal_value>]"
     echo "   Octal escape sequence generator: print all octal escape sequences"
     echo "   between the lower value and the upper value.  If a second value"
     echo "   isn't supplied, print eight characters."
     echo "   1998 - Giles Orr, no warranty."
     exit 1
  }

  if [ "$#" -eq "0" ]
  then
     echo -e "\033[1;31mPlease supply one or two values.\033[0m"
     usage
  fi
  let lower_val=${1}
  if [ "$#" -eq "1" ]
  then
     #   If they don't supply a closing value, give them eight characters.
     upper_val=$(echo -e "obase=8 \n ibase=8 \n $lower_val+10 \n quit" | bc)
  else
     let upper_val=${2}
  fi
  if [ "$#" -gt "2" ]
  then
     echo -e "\033[1;31mPlease supply two values.\033[0m"
     echo
     usage
  fi
  if [ "${lower_val}" -gt "${upper_val}" ]
  then
     echo -e "\033[1;31m${lower_val} is larger than ${upper_val}."
     echo
     usage
  fi
  if [ "${upper_val}" -gt "777" ]
     then
     echo -e "\033[1;31mValues cannot exceed 777.\033[0m"
     echo
     usage
  fi

  let i=$lower_val
  let line_count=1
  let limit=$upper_val
  while [ "$i" -lt "$limit" ]
  do
     octal_escape="\\$i"
     echo -en "$i:'$octal_escape' "
     if [ "$line_count" -gt "7" ]
     then
        echo
        #   Put a hard return in.
        let line_count=0
     fi
     let i=$(echo -e "obase=8 \n ibase=8 \n $i+1 \n quit" | bc)
     let line_count=$line_count+1
  done
  echo
  ______________________________________________________________________


  You can also use xfd to display all the characters in an X font, with
  the command "xfd -fn <fontname>".  Clicking on any given character
  will give you lots of information about that character, including its
  octal value.  The script given above will be useful on the console,
  and if you aren't sure of the current font name.



  8.  The Bash Prompt Package

  8.1.  Availability

  The Bash Prompt package is available at http://bash.current.nu, and is
  the work of several people, co-ordinated by Rob Current (aka
  BadLandZ).  The package is an early beta, but offers a simple way of
  using multiple prompts (or themes), allowing you to set prompts for
  login shells, and for subshells (ie. putting PS1 strings in
  ~/.bash_profile and ~/.bashrc).  Most of the themes use the extended
  VGA character set, so they look bad unless they're used with VGA fonts
  (which aren't the default on most systems).


  8.2.  Xterm Fonts

  To use some of the most attractive prompts in the Bash Prompt package,
  you need to get and install fonts that support the character sets
  expected by the prompts.  These are "VGA Fonts," which support
  different character sets than regular Xterm fonts.  Standard Xterm
  fonts support an extended alphabet, including a lot of letters with
  accents.  In VGA fonts, this material is replaced by graphical
  characters - blocks, dots, lines.  I asked for an explanation of this
  difference, and Srgio Vale e Pace ([email protected]) wrote me:



       I love computer history so here goes:


       When IBM designed the first PC they needed some character
       codes to use, so they got the ASCII character table (128
       numbers, letters, and some punctuation) and to fill a byte
       addressed table they added 128 more characters.  Since the
       PC was designed to be a home computer, they fill the
       remaining 128 characters with dots, lines, points, etc, to
       be able to do borders, and grayscale effects (remember that
       we are talking about 2 color graphics).


       Time passes, PCs become a standard, IBM creates more
       powerful systems and the VGA standard is born, along with
       256 colour graphics, and IBM continues to include their IBM-
       ASCII characters table.


       More time passes, IBM has lost their leadership in the PC
       market, and the OS authors dicover that there are other
       languages in the world that use non-english characters, so
       they add international alphabet support in their systems.
       Since we now have bright and colorful screens, we can trash
       the dots, lines, etc. and use their space for accented
       characters and some greek letters, which you'll see in
       Linux.



  8.3.  Changing the Xterm Font

  Getting and installing these fonts is a somewhat involved process.
  First, retrieve the font(s).  Next, ensure they're .pcf or .pcf.gz
  files.  If they're .bdf files, investigate the "bdftopcf" command (ie.
  read the man page).  Drop the .pcf or .pcf.gz files into the
  /usr/X11R6/lib/X11/fonts/misc dir (this is the correct directory for
  RedHat 5.1 and Slackware 3.4, it may be different on other
  distributions).  "cd" to that directory, and run the "mkfontdir"
  command.  Then run "xset fp rehash".  Sometimes it's a good idea to go
  into the fonts.alias file in the same directory, and create shorter
  alias names for the fonts.


  To use the new fonts, you start your Xterm program of choice with the
  appropriate command to your Xterm, which can be found either in the
  man page or by using the "--help" parameter on the command line.
  Popular terms would be used as follows:



       xterm -font <fontname>



  OR


       xterm -fn <fontname> -fb <fontname-bold>
       Eterm -F <fontname>
       rxvt -fn <fontname>



  VGA fonts are available from Stumpy's ANSI Fonts page at
  http://home.earthlink.net/~us5zahns/enl/ansifont.html (which I have
  borrowed from extensively while writing this).



  9.  Loading a Different Prompt

  9.1.  Loading a Different Prompt, Later

  The explanations in this HOWTO have shown how to make PS1 environment
  variables, or how to incorporate those PS1 and PS2 strings into
  functions that could be called by ~/.bashrc or as a theme by the
  bashprompt package.


  Using the bashprompt package, you would type bashprompt -i to see a
  list of available themes.  To set the prompt in future login shells
  (primarily the console, but also telnet and Xterms, depending on how
  your Xterms are set up), you would type bashprompt -l themename.
  bashprompt then modifies your ~/.bash_profile to call the requested
  theme when it starts.  To set the prompt in future subshells (usually
  Xterms, rxvt, etc.), you type bashprompt -s themename, and bashprompt
  modifies your ~/.bashrc file to call the appropriate theme at startup.


  See also ``Setting the PS? Strings Permanently'' for Johan Kullstam's
  note regarding the importance of putting the PS?  strings in ~/.bashrc
  .


  9.2.  Loading a Different Prompt, Immediately

  You can change the prompt in your current terminal (using the example
  "elite" function above) by typing "source elite" followed by "elite"
  (assuming that the elite function file is the working directory).
  This is somewhat cumbersome, and leaves you with an extra function
  (elite) in your environment space - if you want to clean up the
  environment, you would have to type "unset elite" as well.  This would
  seem like an ideal candidate for a small shell script, but a script
  doesn't work here because the script cannot change the environment of
  your current shell: it can only change the environment of the subshell
  it runs in.  As soon as the script stops, the subshell goes away, and
  the changes the script made to the environment are gone.  What can
  change environment variables of your current shell are environment
  functions.  The bashprompt package puts a function called
  "callbashprompt" into your environment, and, while they don't document
  it, it can be called to load any bashprompt theme on the fly.  It
  looks in the theme directory it installed (the theme you're calling
  has to be there), sources the function you asked for, loads the
  function, and then unsets the function, thus keeping your environment
  uncluttered.  "callbashprompt" wasn't intended to be used this way,
  and has no error checking, but if you keep that in mind, it works
  quite well.



  10.  Loading Prompt Colours Dynamically

  10.1.  A "Proof of Concept" Example

  This is a "proof of concept" more than an attractive prompt: changing
  colours within the prompt dynamically.  In this example, the colour of
  the host name changes depending on the load (as a warning).



  ______________________________________________________________________
  #!/bin/bash
  #   "hostloadcolour" - 17 October 98, by Giles
  #
  #   The idea here is to change the colour of the host name in the prompt,
  #   depending on a threshold load value.

  # THRESHOLD_LOAD is the value of the one minute load (multiplied
  # by one hundred) at which you want
  # the prompt to change from COLOUR_LOW to COLOUR_HIGH
  THRESHOLD_LOAD=200
  COLOUR_LOW='1;34'
            # light blue
  COLOUR_HIGH='1;31'
             # light red

  function prompt_command {
  ONE=$(uptime | sed -e "s/.*load average: \(.*\...\), \(.*\...\), \(.*\...\)/\1/" -e "s/ //g")
  #   Apparently, "scale" in bc doesn't apply to multiplication, but does
  #   apply to division.
  ONEHUNDRED=$(echo -e "scale=0 \n $ONE/0.01 \nquit \n" | bc)
  if [ $ONEHUNDRED -gt $THRESHOLD_LOAD ]
  then
      HOST_COLOUR=$COLOUR_HIGH
          # Light Red
  else
      HOST_COLOUR=$COLOUR_LOW
          # Light Blue
  fi
  }

  function hostloadcolour {

  PROMPT_COMMAND=prompt_command
  PS1="[$(date +%H%M)][\[email protected]\[\033[\$(echo -n \$HOST_COLOUR)m\]\h\[\033[0m\]:\w]$ "
  }
  ______________________________________________________________________



  Using your favorite editor, save this to a file named
  "hostloadcolour".  If you have the Bashprompt package installed, this
  will work as a theme.  If you don't, type source hostloadcolour and
  then hostloadcolour.  Either way, "prompt_command" becomes a function
  in your environment.  If you examine the code, you will notice that
  the colours ($COLOUR_HIGH and $COLOUR_LOW) are set using only a
  partial colour code, ie. "1;34" instead of "\[\033[1;34m\]", which I
  would have preferred.  I have been unable to get it to work with the
  complete code.  Please let me know if you manage this.



  11.  Prompt Code Snippets

  This section shows how to put various pieces of information into the
  Bash prompt.  There are an infinite number of things that could be put
  in your prompt.  Feel free to send me examples, I will try to include
  what I think will be most widely used.  If you have an alternate way
  to retrieve a piece of information here, and feel your method is more
  efficient, please contact me.  It's easy to write bad code, I do it
  often, but it's great to write elegant code, and a pleasure to read
  it.  I manage it every once in a while, and would love to have more of
  it to put in here.

  To incorporate shell code in prompts, it has to be escaped.  Usually,
  this will mean putting it inside \$(<command>) so that the output of
  command is substituted each time the prompt is generated.


  11.1.  Built-in Escape Sequences

  See ``Bash Prompt Escape Sequences'' for a complete list of built-in
  escape sequences.  This list is taken directly from the Bash man page,
  so you can also look there.


  11.2.  Date and Time

  If you don't like the built-ins for date and time, extracting the same
  information from the date command is relatively easy.  Examples
  already seen in this HOWTO include date +%H%M, which will put in the
  hour in 24 hour format, and the minute.  date "+%A, %d %B %Y" will
  give something like "Sunday, 06 June 1999".  For a full list of the
  interpreted sequences, type date --help or man date.


  11.3.  Counting Files in the Current Directory

  To determine how many files there are in the current directory, put in
  ls -l | wc -l.  This uses wc wordcount to do a count of the number of
  lines (-l) in the output of ls -l.  It doesn't count dotfiles.  If you
  want to count only files and NOT include symbolic links (just an
  example of what else you could do), you could use ls -l | grep -v ^l |
  wc -l.  Here, grep checks for any line beginning with "l" (indicating
  a link), and discards that line (-v).


  11.4.  Total Bytes in the Current Directory

  If you want to know how much space the contents of the current
  directory take up, you can use something like the following:



  ______________________________________________________________________
  # The sed command replaces all the spaces with only one space.
  # cut -d" " -f5 : -d determines a delimiter, which means that (in
  # this case) a space begins a new column.
  # -f says to take out a certain column, in this case the fifth one

  let TotalBytes=0

  for Bytes in $(ls -l | grep "^-" | sed -e "s/ \+/ /g" | cut -d" " -f5)
  do
     let TotalBytes=$TotalBytes+$Bytes
  done

  # The if...fi's give a more specific output in byte, kilobyte, megabyte,
  # and gigabyte

  if [ $TotalBytes -lt 1024 ]; then
     TotalSize=$(echo -e "scale=3 \n$TotalBytes \nquit" | bc)
  else if [ $TotalBytes -lt 1048576 ]; then
     TotalSize=$(echo -e "scale=3 \n$TotalBytes/1024 \nquit" | bc)
  else if [ $TotalBytes -lt 1073741824 ]; then
     TotalSize=$(echo -e "scale=3 \n$TotalBytes/1048576 \nquit" | bc)
  else
     TotalSize=$(echo -e "scale=3 \n$TotalBytes/1073741824 \nquit" | bc)
  fi
  fi
  fi
  ______________________________________________________________________



  Code courtesy of Sam Schmit ([email protected]) and his uncle Jean-Paul, who
  ironed out a fairly major bug in my original code, and just generally
  cleaned it up.


  11.5.  Checking the Current TTY

  The tty command returns the filename of the terminal connected to
  standard input.  This comes in two formats on the Linux systems I have
  used, either "/dev/tty4" or "/dev/pts/2".  I have taken to using a
  more general solution to this: tty | sed -e "s:/dev/::", which removes
  the leading "/dev/".  Older systems (in my experience, RedHat through
  5.2) returned only filenames in the "/dev/tty4" format, so I used tty
  | sed -e "s/.*tty\(.*\)/\1/".


  An alternative method: ps aux | grep $$ | awk '{ print $7 }'.


  11.6.  Suspended Job Count

  To find out how many suspended jobs you have, use jobs | wc -l | awk
  otherwise include blank spaces that waste space in a prompt.  If you
  start netscape from an xterm, this will also be counted.  If you want
  to avoid that, and only count stopped jobs, use jobs -s instead.  Type
  help jobs for more info on jobs.  jobs will always return nothing to a
  pipe in version 2.02 of Bash: this problem is not present in any other
  version.


  11.7.  Uptime and Load

  Current load is taken from the uptime command.  What I use at the
  moment is uptime | sed -e "s/.*load average: \(.*\...\), .*\...,
  .*\.../\1/" -e "s/ //g" which is clunky in the extreme, but works.
  Replacements welcome.  uptime can also be used in a very similar
  manner to find out how long the machine has been up (obviously) or how
  many users are logged in, and the data could be massaged with sed to
  look the way you want it to.


  11.8.  Number of Processes

  ps ax | wc -l | tr -d " " OR ps ax | wc -l | awk each case, tr or awk
  or sed is used to remove the undesirable whitespace.


  11.9.  Controlling the Width of $PWD

  Unix allows long file names, which can lead to the value of $PWD being
  very long.  Some people (notably the default RedHat prompt) choose to
  use the basename of the current working directory (ie. "giles" if
  $PWD="/home/giles").  I like more info than that, but it's often
  desirable to limit the length of the directory name, and it makes the
  most sense to truncate on the left.


  ______________________________________________________________________
  #   How many characters of the $PWD should be kept
  local pwd_length=30
  if [ $(echo -n $PWD | wc -c | tr -d " ") -gt $pwd_length ]
  then
     newPWD="...$(echo -n $PWD | sed -e "s/.*\(.\{$pwd_length\}\)/\1/")"
  else
     newPWD="$(echo -n $PWD)"
  fi
  ______________________________________________________________________



  The above code can be executed as part of PROMPT_COMMAND, and the
  environment variable generated (newPWD) can then be included in the
  prompt.


  11.10.  Laptop Power

  Again, this isn't elegant, but it works (most of the time).  If you
  have a laptop with APM installed, try power=$(apm | sed -e "s/.*:
  \([1-9][0-9]*\)%/\1/" | tr -d " ") executed from PROMPT_COMMAND to
  create an environment variable you can add to your prompt.  This will
  indicate percentage power remaining.


  11.11.  Having the Prompt Ignored on Cut and Paste


  This one is weird but cool.  Rory Toma ([email protected]) wrote to
  suggest a prompt like this: : [email protected] ; .  How is this useful?
  Well, if you type a command after the prompt (odd idea, that), you can
  triple click on that line (in Linux, anyway) to highlight the whole
  line, then paste that line in front of another prompt, and the stuff
  between the ":" and the """ is ignored, like so:



  ______________________________________________________________________
  : [email protected] ; uptime
    5:15pm  up 6 days, 23:04,  2 users,  load average: 0.00, 0.00, 0.00
  : [email protected] ; : [email protected] ; uptime
    5:15pm  up 6 days, 23:04,  2 users,  load average: 0.00, 0.00, 0.00
  ______________________________________________________________________



  The prompt is a no-op, and if your PS2 is set to a space, multiple
  lines can be cut and pasted as well.


  11.12.  Setting the Window Title and Icon Title Separately

  A suggestion from Charles Lepple ([email protected]) on setting
  the window title of the Xterm and the title of the corresponding icon
  separately (first check out the earlier section ``Xterm Title Bar
  Manipulations'').  He uses this under WindowMaker because the title
  that's appropriate for an Xterm is usually too long for a 64x64 icon.
  "\[\e]1;icon-title\007\e]2;main-title\007\]".  He says to set this in
  the prompt command because "I tried putting the string in PS1, but it
  causes flickering under some window managers because it results in
  setting the prompt multiple times when you are editing a multi-line
  command (at least under bash 1.4.x -- and I was too lazy to fully
  explore the reasons behind it)."  I had no trouble with it in the PS1
  string, but didn't use any multi-line commands.  He also points out
  that it works under xterm, xwsh, and dtterm, but not gnome-terminal
  (which uses only the main title).  I also found it to work with rxvt,
  but not kterm.



  12.  Example Prompts

  12.1.  Over time, many people have e-mailed me excellent examples, and
  I've written some interesting ones myself.  There are far too many to
  include here, so I have put all of the examples together into some web
  pages which can be seen athttp://www.interlog.com/~giles/bash-
  prompt/prompts.  Web pages also allow me to include pictures, which I
  can't include in a standard HOWTO.  All of the examples given here
  except Bradley Alexander's "Prompts Depending on Connection Types" can
  also be seen on the web.  Examples on the Web

  12.2.  A "Lightweight" Prompt



  ______________________________________________________________________

  function proml {
  local BLUE="\[\033[0;34m\]"
  local RED="\[\033[0;31m\]"
  local LIGHT_RED="\[\033[1;31m\]"
  local WHITE="\[\033[1;37m\]"
  local NO_COLOUR="\[\033[0m\]"
  case $TERM in
      xterm*)
          TITLEBAR='\[\033]0;\[email protected]\h:\w\007\]'
          ;;
      *)
          TITLEBAR=""
          ;;
  esac

  PS1="${TITLEBAR}\
  $BLUE[$RED\$(date +%H%M)$BLUE]\
  $BLUE[$LIGHT_RED\[email protected]\h:\w$BLUE]\
  $WHITE\$$NO_COLOUR "
  PS2='> '
  PS4='+ '
  }
  ______________________________________________________________________



  12.3.  Elite from Bashprompt Themes

  Note that this requires a VGA font.


  ______________________________________________________________________

  # Created by KrON from windowmaker on IRC
  # Changed by Spidey 08/06
  function elite {
  PS1="\[\033[31m\]\332\304\[\033[34m\](\[\033[31m\]\u\[\033[34m\]@\[\033[31m\]\h\
  \[\033[34m\])\[\033[31m\]-\[\033[34m\](\[\033[31m\]\$(date +%I:%M%P)\
  \[\033[34m\]-:-\[\033[31m\]\$(date +%m)\[\033[34m\033[31m\]/\$(date +%d)\
  \[\033[34m\])\[\033[31m\]\304-\[\033[34m]\\371\[\033[31m\]-\371\371\
  \[\033[34m\]\372\n\[\033[31m\]\300\304\[\033[34m\](\[\033[31m\]\W\[\033[34m\])\
  \[\033[31m\]\304\371\[\033[34m\]\372\[\033[00m\]"
  PS2="> "
  }
  ______________________________________________________________________



  12.4.  A "Power User" Prompt

  I actually do use this prompt, but it results in noticeable delays in
  the appearance of the prompt on a single-user PII-400, so I wouldn't
  recommend using it on a multi-user P-100 or anything ...  Look at it
  for ideas, rather than as a practical prompt.



  ______________________________________________________________________

  #!/bin/bash
  #----------------------------------------------------------------------
  #       POWER USER PROMPT "pprom2"
  #----------------------------------------------------------------------
  #
  #   Created August 98, Last Modified 9 November 98 by Giles
  #
  #   Problem: when load is going down, it says "1.35down-.08", get rid
  #   of the negative

  function prompt_command
  {
  #   Create TotalMeg variable: sum of visible file sizes in current directory
  local TotalBytes=0
  for Bytes in $(ls -l | grep "^-" | cut -c30-41)
  do
      let TotalBytes=$TotalBytes+$Bytes
  done
  TotalMeg=$(echo -e "scale=3 \nx=$TotalBytes/1048576\n if (x<1) {print \"0\"} \n print x \nquit" | bc)

  #      This is used to calculate the differential in load values
  #      provided by the "uptime" command.  "uptime" gives load
  #      averages at 1, 5, and 15 minute marks.
  #
  local one=$(uptime | sed -e "s/.*load average: \(.*\...\), \(.*\...\), \(.*\...\)/\1/" -e "s/ //g")
  local five=$(uptime | sed -e "s/.*load average: \(.*\...\), \(.*\...\), \(.*\...\).*/\2/" -e "s/ //g")
  local diff1_5=$(echo -e "scale = scale ($one) \nx=$one - $five\n if (x>0) {print \"up\"} else {print \"down\"}\n print x \nquit \n" | bc)
  loaddiff="$(echo -n "${one}${diff1_5}")"

  #   Count visible files:
  let files=$(ls -l | grep "^-" | wc -l | tr -d " ")
  let hiddenfiles=$(ls -l -d .* | grep "^-" | wc -l | tr -d " ")
  let executables=$(ls -l | grep ^-..x | wc -l | tr -d " ")
  let directories=$(ls -l | grep "^d" | wc -l | tr -d " ")
  let hiddendirectories=$(ls -l -d .* | grep "^d" | wc -l | tr -d " ")-2
  let linktemp=$(ls -l | grep "^l" | wc -l | tr -d " ")
  if [ "$linktemp" -eq "0" ]
  then
      links=""
  else
      links=" ${linktemp}l"
  fi
  unset linktemp
  let devicetemp=$(ls -l | grep "^[bc]" | wc -l | tr -d " ")
  if [ "$devicetemp" -eq "0" ]
  then
      devices=""
  else
      devices=" ${devicetemp}bc"
  fi
  unset devicetemp

  }

  PROMPT_COMMAND=prompt_command

  function pprom2 {

  local        BLUE="\[\033[0;34m\]"
  local  LIGHT_GRAY="\[\033[0;37m\]"
  local LIGHT_GREEN="\[\033[1;32m\]"
  local  LIGHT_BLUE="\[\033[1;34m\]"
  local  LIGHT_CYAN="\[\033[1;36m\]"
  local      YELLOW="\[\033[1;33m\]"
  local       WHITE="\[\033[1;37m\]"
  local         RED="\[\033[0;31m\]"
  local   NO_COLOUR="\[\033[0m\]"

  case $TERM in
      xterm*)
          TITLEBAR='\[\033]0;\[email protected]\h:\w\007\]'
          ;;
      *)
          TITLEBAR=""
          ;;
  esac

  PS1="$TITLEBAR\
  $BLUE[$RED\$(date +%H%M)$BLUE]\
  $BLUE[$RED\[email protected]\h$BLUE]\
  $BLUE[\
  $LIGHT_GRAY\${files}.\${hiddenfiles}-\
  $LIGHT_GREEN\${executables}x \
  $LIGHT_GRAY(\${TotalMeg}Mb) \
  $LIGHT_BLUE\${directories}.\
  \${hiddendirectories}d\
  $LIGHT_CYAN\${links}\
  $YELLOW\${devices}\
  $BLUE]\
  $BLUE[${WHITE}\${loaddiff}$BLUE]\
  $BLUE[\
  $WHITE\$(ps ax | wc -l | sed -e \"s: ::g\")proc\
  $BLUE]\
  \n\
  $BLUE[$RED\$PWD$BLUE]\
  $WHITE\$\
  \
  $NO_COLOUR "
  PS2='> '
  PS4='+ '
  }
  ______________________________________________________________________



  12.5.  Prompt Depending on Connection Type

  Bradley M Alexander ([email protected]) had the excellent idea of
  reminding his users what kind of connection they were using to his
  machine(s), so he colour-codes prompts dependent on connection type.
  Here's the bashrc he supplied to me:



  ______________________________________________________________________

  # /etc/bashrc

  # System wide functions and aliases
  # Environment stuff goes in /etc/profile

  # For some unknown reason bash refuses to inherit
  # PS1 in some circumstances that I can't figure out.
  # Putting PS1 here ensures that it gets loaded every time.

  # Set up prompts. Color code them for logins. Red for root, white for
  # user logins, green for ssh sessions, cyan for telnet,
  # magenta with red "(ssh)" for ssh + su, magenta for telnet.
  THIS_TTY=tty`ps aux | grep $$ | grep bash | awk '{ print $7 }'`
  SESS_SRC=`who | grep $THIS_TTY | awk '{ print $6 }'`

  SSH_FLAG=0
  SSH_IP=`echo $SSH_CLIENT | awk '{ print $1 }'`
  if [ $SSH_IP ] ; then
    SSH_FLAG=1
  fi
  SSH2_IP=`echo $SSH2_CLIENT | awk '{ print $1 }'`
  if [ $SSH2_IP ] ; then
    SSH_FLAG=1
  fi
  if [ $SSH_FLAG -eq 1 ] ; then
    CONN=ssh
  elif [ -z $SESS_SRC ] ; then
    CONN=lcl
  elif [ $SESS_SRC = "(:0.0)" -o $SESS_SRC = "" ] ; then
    CONN=lcl
  else
    CONN=tel
  fi

  # Okay...Now who we be?
  if [ `/usr/bin/whoami` = "root" ] ; then
    USR=priv
  else
    USR=nopriv
  fi

  #Set some prompts...
  if [ $CONN = lcl -a $USR = nopriv ] ; then
    PS1="[\u \W]\\$ "
  elif [ $CONN = lcl -a $USR = priv ] ; then
    PS1="\[\033[01;31m\][\w]\\$\[\033[00m\] "
  elif [ $CONN = tel -a $USR = nopriv ] ; then
    PS1="\[\033[01;34m\][\[email protected]\h \W]\\$\[\033[00m\] "
  elif [ $CONN = tel -a $USR = priv ] ; then
    PS1="\[\033[01;30;45m\][\[email protected]\h \W]\\$\[\033[00m\] "
  elif [ $CONN = ssh -a $USR = nopriv ] ; then
    PS1="\[\033[01;32m\][\[email protected]\h \W]\\$\[\033[00m\] "
  elif [ $CONN = ssh -a $USR = priv ] ; then
    PS1="\[\033[01;35m\][\[email protected]\h \W]\\$\[\033[00m\] "
  fi

  # PS1="[\[email protected]\h \W]\\$ "
  export PS1
  alias which="type -path"
  alias dir="ls -lF --color"
  alias dirs="ls -lFS --color"
  alias h=history
  ______________________________________________________________________

  12.6.  A Prompt the Width of Your Term

  A friend complained that he didn't like having a prompt that kept
  changing size because it had $PWD in it, so I wrote this prompt that
  adjusts its size to exactly the width of your term, with the working
  directory on the top line of two.



  ______________________________________________________________________

  #!/bin/bash

  #   termwide prompt
  #      by Giles - created 2 November 98
  #
  #   The idea here is to have the upper line of this two line prompt
  #   always be the width of your term.  Do this by calculating the
  #   width of the text elements, and putting in fill as appropriate
  #   or left-truncating $PWD.
  #

  function prompt_command {

  TERMWIDTH=${COLUMNS}

  #   Calculate the width of the prompt:

  hostnam=$(echo -n $HOSTNAME | sed -e "s/[\.].*//")
  #   "whoami" and "pwd" include a trailing newline
  usernam=$(whoami)
  let usersize=$(echo -n $usernam | wc -c | tr -d " ")
  newPWD="${PWD}"
  let pwdsize=$(echo -n ${newPWD} | wc -c | tr -d " ")
  #   Add all the accessories below ...
  let promptsize=$(echo -n "--(${usernam}@${hostnam})---(${PWD})--" \
                   | wc -c | tr -d " ")
  let fillsize=${TERMWIDTH}-${promptsize}
  fill=""
  while [ "$fillsize" -gt "0" ]
  do
     fill="${fill}-"
     let fillsize=${fillsize}-1
  done

  if [ "$fillsize" -lt "0" ]
  then
     let cut=3-${fillsize}
     newPWD="...$(echo -n $PWD | sed -e "s/\(^.\{$cut\}\)\(.*\)/\2/")"
  fi
  }

  PROMPT_COMMAND=prompt_command

  function termwide {

  local GRAY="\[\033[1;30m\]"
  local LIGHT_GRAY="\[\033[0;37m\]"
  local WHITE="\[\033[1;37m\]"
  local NO_COLOUR="\[\033[0m\]"

  local LIGHT_BLUE="\[\033[1;34m\]"
  local YELLOW="\[\033[1;33m\]"

  case $TERM in
      xterm*)
          TITLEBAR='\[\033]0;\[email protected]\h:\w\007\]'
          ;;
      *)
          TITLEBAR=""
          ;;
  esac

  PS1="$TITLEBAR\
  $YELLOW-$LIGHT_BLUE-(\
  $YELLOW\${usernam}[email protected]$YELLOW\${hostnam}\
  ${LIGHT_BLUE})-${YELLOW}-\${fill}${LIGHT_BLUE}-(\
  $YELLOW\${newPWD}\
  $LIGHT_BLUE)-$YELLOW-\
  \n\
  $YELLOW-$LIGHT_BLUE-(\
  $YELLOW\$(date +%H%M)$LIGHT_BLUE:$YELLOW\$(date \"+%a,%d %b %y\")\
  $LIGHT_BLUE:$WHITE\$$LIGHT_BLUE)-\
  $YELLOW-\
  $NO_COLOUR "

  PS2="$LIGHT_BLUE-$YELLOW-$YELLOW-$NO_COLOUR "

  }
  ______________________________________________________________________



  12.7.  The Elegant Useless Clock Prompt

  This is one of the more attractive (and useless) prompts I've made.
  Because many X terminal emulators don't implement cursor position save
  and restore, the alternative when putting a clock in the upper right
  corner is to anchor the cursor at the bottom of the terminal.  This
  builds on the idea of the "termwide" prompt above, drawing a line up
  the right side of the screen from the prompt to the clock.  A VGA font
  is required.


  Note: There is an odd substitution in here, that may not print
  properly being translated from SGML to other formats: I had to
  substitute the screen character for \304 - I would normally have just
  included the sequence "\304", but it was necessary to make this
  substitution in this case.



  ______________________________________________________________________

  #!/bin/bash

  #   This prompt requires a VGA font.  The prompt is anchored at the bottom
  #   of the terminal, fills the width of the terminal, and draws a line up
  #   the right side of the terminal to attach itself to a clock in the upper
  #   right corner of the terminal.

  function prompt_command {
  #   Calculate the width of the prompt:
  hostnam=$(echo -n $HOSTNAME | sed -e "s/[\.].*//")
  #   "whoami" and "pwd" include a trailing newline
  usernam=$(whoami)
  newPWD="${PWD}"
  #   Add all the accessories below ...
  let promptsize=$(echo -n "--(${usernam}@${hostnam})---(${PWD})-----" \
                   | wc -c | tr -d " ")
  #   Figure out how much to add between [email protected] and PWD (or how much to
  #   remove from PWD)
  let fillsize=${COLUMNS}-${promptsize}
  fill=""
  #   Make the filler if prompt isn't as wide as the terminal:
  while [ "$fillsize" -gt "0" ]
  do
     fill="${fill}"
     # The A with the umlaut over it (it will appear as a long dash if
     # you're using a VGA font) is \304, but I cut and pasted it in
     # because Bash will only do one substitution - which in this case is
     # putting $fill in the prompt.
     let fillsize=${fillsize}-1
  done
  #   Right-truncate PWD if the prompt is going to be wider than the terminal:
  if [ "$fillsize" -lt "0" ]
  then
     let cutt=3-${fillsize}
     newPWD="...$(echo -n $PWD | sed -e "s/\(^.\{$cutt\}\)\(.*\)/\2/")"
  fi
  #
  #   Create the clock and the bar that runs up the right side of the term
  #
  local LIGHT_BLUE="\033[1;34m"
  local     YELLOW="\033[1;33m"
  #   Position the cursor to print the clock:
  echo -en "\033[2;$((${COLUMNS}-9))H"
  echo -en "$LIGHT_BLUE($YELLOW$(date +%H%M)$LIGHT_BLUE)\304$YELLOW\304\304\277"
  local i=${LINES}
  echo -en "\033[2;${COLUMNS}H"
  #   Print vertical dashes down the side of the terminal:
  while [ $i -ge 4 ]
  do
     echo -en "\033[$(($i-1));${COLUMNS}H\263"
     let i=$i-1
  done

  let prompt_line=${LINES}-1
  #   This is needed because doing \${LINES} inside a Bash mathematical
  #   expression (ie. $(())) doesn't seem to work.
  }

  PROMPT_COMMAND=prompt_command

  function clock3 {
  local LIGHT_BLUE="\[\033[1;34m\]"
  local     YELLOW="\[\033[1;33m\]"
  local      WHITE="\[\033[1;37m\]"
  local LIGHT_GRAY="\[\033[0;37m\]"
  local  NO_COLOUR="\[\033[0m\]"

  case $TERM in
      xterm*)
          TITLEBAR='\[\033]0;\[email protected]\h:\w\007\]'
          ;;
      *)
          TITLEBAR=""
          ;;
  esac

  PS1="$TITLEBAR\
  \[\033[\${prompt_line};0H\]
  $YELLOW\332$LIGHT_BLUE\304(\
  $YELLOW\${usernam}[email protected]$YELLOW\${hostnam}\
  ${LIGHT_BLUE})\304${YELLOW}\304\${fill}${LIGHT_BLUE}\304(\
  $YELLOW\${newPWD}\
  $LIGHT_BLUE)\304$YELLOW\304\304\304\331\
  \n\
  $YELLOW\300$LIGHT_BLUE\304(\
  $YELLOW\$(date \"+%a,%d %b %y\")\
  $LIGHT_BLUE:$WHITE\$$LIGHT_BLUE)\304\
  $YELLOW\304\
  $LIGHT_GRAY "

  PS2="$LIGHT_BLUE\304$YELLOW\304$YELLOW\304$NO_COLOUR "

  }
  ______________________________________________________________________