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)][\u@\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:
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 (ddui@iee.org) 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='\[\033]0;\u@\h:\w\007\]'
;;
*)
local TITLEBAR=""
;;
esac
local GRAD1=$(tty|cut -d/ -f3)
PS1="$TITLEBAR\
$GRAY-$CYAN-$LIGHT_CYAN(\
$CYAN\u$GRAY@$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:
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='\[\033]0;\u@\h:\w\007\]'
;;
*)
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\u@\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.
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.
