Custom Bash prompt is overwriting itself

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1) I would like to know why it is overwriting my prompt

Because every non-printable characters have to be escaped by \[ and \] otherwise readline cannot keep track of the cursor position correctly.

You must put \[ and \] around any non-printing escape sequences in your prompt.
Without the \[ \] bash will think the bytes which constitute the escape sequences for the color codes will actually take up space on the screen, so bash won’t be able to know where the cursor actually is.

\[ Begin a sequence of non-printing characters. (like color escape sequences). This
allows bash to calculate word wrapping correctly.

\] End a sequence of non-printing characters.
— BashFAQ

…note the escapes for the non printing characters, these ensure that readline can keep track of the cursor position correctly. — ss64.com

2) How to fix this issue when function is used

If you want to set colours inside a function whose output is used in PS you have two options.

  • Either escape the whole function call:

    PS1='\[ $(formattedGitBranch) \] '

  • Or replace the non-printing Escape sequences inside echo. That is, replace:

    \[ and \] with \001 \002

    (thanks to user grawity!)

  • echo -e is not aware of bash’s \[ \] so you have to substitute these with \001 & \002 ASCII control codes to delimit non-printable chars from printable:

    function formattedGitBranch { echo -e "\001\e[0;91m\002 ($_branch)"; }
    PS1='$(formattedGitBranch) '

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