How to set a conditional newline in PS1?

Question

I am trying to set PS1 so that it prints out something just right after login, but preceded with a newline later.

Suppose export PS1=\"\\h:\\W \\u

Answer 1

Try the following:

function __ps1_newline_login {
  if [[ -z "${PS1_NEWLINE_LOGIN}" ]]; then
    PS1_NEWLINE_LOGIN=true
  else
    printf '\n'
  fi
}

PROMPT_COMMAND='__ps1_newline_login'
export PS1="\h:\W \u\$ "

Explanation:

• PROMPT_COMMAND is a special bash variable which is executed every time before the prompt is set.
• You need to use the -z flag to check if the length of a string is 0.