[GRLUG] Custom $PS1 settings

[Ben Rousch]

----- "Rick Vargo" <rick at vargo.org> wrote:
> Some of you guys need to get outside more.  See the sun!  Bunch of
> geeks!  :)  J/K
> 
> Rick
> 
> 
> Raymond McLaughlin wrote:
> > Michael Mol wrote:
> >   
> >> Like, I suspect, many people, I have custom settings for PS1 in my
> >> ~/.bashrc file:
> >>
> >> PS1="\u@\H\w\n\t \$ "
> >>
> >> This give me a conventient prompt:
> >>
> >> shortcircuit at caterpillar~
> >> 22:53:34 $
> >>
> >> I see my username, the name of the machine I'm logged into, my
> path,
> >> the current time, and whether or not I'm logged in as root.
> >>
> >> In the past, I've had prompts which executed scripts that displayed
> an
> >> indicator to tell me whether or not certain accounts were logged
> in.
> >>
> >> What do you use for a prompt?  What's the most unique prompt you've
> ever used?
> >>     
> >
> > Glad you asked, this is one of my favorite hacks. Most people know
> about
> > the $PS1 variable, but few know about the $PROMPT_COMMAND variable.
> > Where $PS1 defines how the prompt line looks, $PROMPT_COMMAND can
> define
> > a script to be run immediately before the command prompt is
> displayed.
> >
> > In my case $PROMPT_COMMAND=prompt_command where 'prompt_command' is
> a
> > function defined in a startup script named .prompt_command which is
> in
> > turned called from a line in .bashrc (test -s ~/.prompt_command &&
> .
> > ~/.prompt_command). In addition to setting $PS1 to show which device
> has
> > the current console, it defines a function prompt_command to write
> > $USERNAME@$HOST:$PWD , in colored text on contrasting background, at
> the
> > top right corner of the display.
> >
> > below is my startup script .prompt_command. I have been tweeking it
> for
> > a couple years. Note that I pasted it as a quotation to guard
> against
> > line wrap mangling. Each line begins with a leading '>' that should
> not
> > be included in the actual script.
> >
> >   
> >> # bash recognizess a variable called PROMPT_COMMAND and, if it is
> set,
> >> # executes whatever it evaluates to. This script needs to be called
> from .bashrc.
> >> # The first part defines a function, 'prompt_command', which
> evaluates
> >> # the current working and directory, (and hostname and username if
> desired), 
> >> # then writes it to the upper right corner of the display in
> contrasting color.
> >> # The variable PROMPT_COMMAND is then set equal to
> 'prompt_command'.
> >> # The second part provides a short prompt string indicating the
> current input device.
> >>
> >> ##############################
> >> # Step 1: Define function.
> >> ##############################
> >> function prompt_command 
> >> {
> >> tput sc   # Save the current cursor position
> >>
> >> # set background, forground color, bold
> >> if [ $UID = 0 ]
> >>   then tput setab 1 ; tput setaf 3 ; tput bold  # yellow text on
> red background for root
> >>   else tput setab 4 ; tput setaf 6 ; tput bold  # cyan text on blue
> background for users
> >> fi
> >>
> >> # Define DIR as current directory, with current users home reduced
> to ~
> >> DIR=$(pwd | sed s?$(echo ~)?~?)
> >>
> >> # OLDDIR is directory string most recently WRITTEN TO THE SCREEN.
> >> # If $OLDDIR longer than the current $DIR it will be necessary to
> clean up artifacts,
> >> # which might remain to the left of the new one, by over-writing
> with blank spaces.
> >> if [ -z $OLDDIR  ]; then OLDDIR=$DIR; fi # $OLDDIR must not be
> empty.
> >> DIFF=$(($(echo $OLDDIR | wc -m)-$(echo $DIR | wc -m)))
> >>
> >> ## Define SPLASH_STRING - pick one
> >> # SPLASH_STRING="$DIR"
> >> # SPLASH_STRING="$HOSTNAME:$DIR"
> >> user=$(echo ~ | sed s?/home?? |sed s?/??)
> >>
> >> SPLASH_STRING="$user@$HOSTNAME:$DIR"
> >>
> >> # Define pad as the total width of the terminal less the length
> >> # of the splash string
> >>  
> >> if [ $DIFF -gt 0 ];
> >>   then
> >>     let pad=$(tput cols)-$(echo $SPLASH_STRING | wc -m)-$DIFF+1
> >>     tput cup 0 $pad  # position the cursor so that the hostname and
> PWD are at top left (Y=0, X=$pad)
> >>     while [ $DIFF -gt 0 ]; do echo -n " "; DIFF=$(($DIFF-1));done
> >>
> >>   else
> >>     let pad=$(tput cols)-$(echo $SPLASH_STRING | wc -m)+1
> >>     tput cup 0 $pad  # position the cursor so that the hostname and
> PWD are at top left (Y=0, X=$pad)
> >> fi
> >>
> >> echo -n "$SPLASH_STRING"   #Show the hostname and present working
> directory.
> >>
> >> OLDDIR=$DIR   # Save directory string for DIFF in next execution.
> >> tput rc   # Return the cursor to the saved position
> >> }
> >>
> >> ########################################
> >> # Step 2: Set variable equal to function
> >> ########################################
> >> PROMPT_COMMAND=prompt_command
> >>
> >> ############################################################
> >> # Step 3: Set prompt string to display current input device
> >> ############################################################
> >>
> >> #Evaluate current logged device from output of 'tty'
> >> tty=$(echo $(tty) |sed s%/dev/%%)
> >>
> >> # Set command prompt to show current console
> >> PS1="$tty \\$ "
> >>     
> >
> >
> >
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> >   
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I got some sun last weekend, now my head is burned and peeling and the magnetic strips on my credit cards are being ground to nothing by sand in my wallet. My bash prompt has never caused such problems for me. I think I will take the sunless option from now on!

-- 
- Ben Rousch