Bash – How to change screen’s hardstatus color based on the logged in user

bashbashrccolorsgnu-screen

I haven't edited/created a .screenrc file in a while, but this is what I'm currently using:

# Turn off the screen startup message
startup_message off

# Define format of bottom navigation/status/date/etc. line
hardstatus alwayslastline "%{yk}[ %H ] %-Lw%50>%{gk}(%{-}%n-%t%{gk})%{-}%+Lw%< %=%{yk}[ %c %d.%m.%Y ]"

# Increase scrollback buffer to 30000 lines
defscrollback 30000

I honestly don't remember what everything in my hardstatus line stands for, but I want to figure out how I could change the hostname color based on the user that is logged in. Is this even possible? Right now, the hostname is yellow when I'm logged in under any user; but I want it to be red if I'm root. Is this something that can be changed in my .bashrc file? I have this in my .bashrc to change new screen window names to the hostname of the server I'm connected to:

# Set screen window title
case "$TERM" in
screen)
  PROMPT_COMMAND='echo -ne "\033k$HOSTNAME\033\\"'
  ;;
esac

Thanks for any help!

EDIT

I've tried adding this to my .bashrc file, but it just puts the ANSI code in-front of the hostname in my screen hardstatus:

case "$TERM" in
screen)
  if (( $UID == 0 )); then
    PROMPT_COMMAND='echo -ne "\033k$FRED$HOSTNAME$RS\033\\"'
  else
    PROMPT_COMMAND='echo -ne "\033k$HOSTNAME\033\\"'
  fi
  ;;
esac

EDIT 2

I've also added the actual ANSI color codes (ex: \[\033[31m\]) and the screen escape codes (ex: %kr) to the above statement in my .bashrc, but neither worked.

EDIT 3

If I use this as the prompt command line, the hostname appears in red in-front of my PS1:

PROMPT_COMMAND='echo -ne "\033[31m$HOSTNAME\033\\"'

If I use the following prompt, the window name changes to the hostname (YES!); but the color remains the default (NO!):

PROMPT_COMMAND='echo -ne "\033[31m\033k$HOSTNAME\033\\"'

I've also tried replacing \033[31m (and just [31m) with the screen color escape (%kr), but that did not work either.

Best Answer

Take a look at this U&L Q&A.

How can you change the GNU screen status line based on hostname?

Specifically this answer, https://unix.stackexchange.com/a/16433/7453.

The general idea is that you maintain 2 different screenrc files with the colors and based on your $USER in your bashrc file you point the environment variableSCREENRC to the one for a given user.

Related Solutions

Bash Command – Printing and Saving the Last Bash Input Command

You can access the just-executed command line with the history built-in. (I have no idea why history 1 prints the just-executed command line but fc -nl -1 prints the previous commmand, as does fc -nl 0.)

PROMPT_COMMAND='echo -en "\033[38;5;2m"; history 1; echo -en "\033[0m\n"'

This prints a number before the command text. Here's a version that removes the number. (It may be incorrect if you go beyond 99999 history lines, I don't know how bash formats the number then.)

prompt_function () {
  local prompt_history="$(history 1)"
  prompt_history=${prompt_history:7}
  echo -En $'\033[38;5;2m'"$prompt_history"$'\033[0m\n'
}
PROMPT_COMMAND=prompt_function

(Note that echo -en ..."$prompt_history"... would expand backslashes in the command line, so I use echo -E and let the shell expansion generate the control characters with $''.).

GNU Screen – How to Change Status Line Based on Hostname

I see two way to do this, the first one is to make a .screenrc file by host.
Like .screenrc_serverA, .screenrc_serverB, ...
In your shell startup script set SCREENRC to something like .screenrc_`hostname`
Of course you can use the source command of screen to include something like .screenrc_default in each custom .screenrc_… files so that they only contains a caption/hardstatus line and not the whole configuration each time.

The second way would be to execute commands like screen -X hardstatus lastline ... (using if tests to execute the command with different value for ... depending of the hostname) in your shell startup script. When you will log on the server, screen -X will do nothing because screen will not yet be launched, but each time you open a new windows in screen the hardstatus will be updated.

Of course the 1st solution is better because the second one will refresh the hardstatus line each time you opened a news windows which is probably useless as the hostname will not have changed.

Best Answer

Related Solutions

Bash Command – Printing and Saving the Last Bash Input Command

GNU Screen – How to Change Status Line Based on Hostname

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