Emoji in bash prompt

I saw this in a colleague’s laptop the other day. He had his bash prompt configured to show a black arrow when things are okay and a red arrow when the last command failed. I fiddled around with my bash prompt to achieve something similar.

This is for Mac by the way, but hopefully that shouldn’t be too important. Originally, I had setup my .bash_profile to use the git prompt:

. /Library/Developer/CommandLineTools/usr/share/git-core/git-completion.bash
. /Library/Developer/CommandLineTools/usr/share/git-core/git-prompt.sh

PS1='\h: \W $(__git_ps1 " (%s)") \u\$ '

To display colors (another thing I was missing), I had to change the PS1 line into PROMPT_COMMAND:

GIT_PS1_SHOWCOLORHINTS="1"
PROMPT_COMMAND='__git_ps1 "\u@\h:\w" "\\\$ "'

As __git_ps1 is just a function that sets PS1, I added my own function in .bash_profile:

__last_err_ps1() {
  local EXIT="$?"
  local RCol='\[\e[0m\]'
  local Red='\[\e[0;31m\]'
  if [ $EXIT != 0 ]; then
    PS1="🚨 ${Red}${EXIT}${RCol} ${PS1}"
  else
    PS1="🆗 ${PS1}"
  fi
}

This function checks the exit code and prepends a text to the PS1 prompt. If the exit code is zero, it adds the OK emoji. Otherwise, it adds an alarm emoji and also shows the exit code in red. I find the visual hint quite useful and showing the exit code saves the extra effort of typing echo $? to see it.

To use it, I modified PROMPT_COMMAND into:

PROMPT_COMMAND='__git_ps1 "\u@\h:\w" "\\\$ " ; __last_err_ps1'

Here’s how it looks like on a terminal:

Hope this helps!