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Extend your bash PS1 with a git branch without breaking your prompt

Adding the current Git branch to Bash PS1 without breaking prompt width calculation.

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I wanted my terminal prompt to show the current branch of the Git repository in which I was working.

Many guides explain how to add a branch name, but the first one I followed left me with a broken Bash prompt. It ignored newlines and behaved strangely whenever the prompt exceeded the terminal width.

The problem was that non-printing color sequences confused Bash’s prompt-width calculation. Wrapping those sequences in \[ and \] tells Bash not to count them as visible characters.

The following commented snippet extends ~/.bash_login, or another Bash startup file that contains user-specific configuration:

# write a function to compute the current git branch
parse_git_branch() {
  local b=$(git symbolic-ref HEAD 2> /dev/null)
  echo -n "${b#refs/heads/}"
}

# set the PS1 variable
PS1="\w\[\e[0;33;49m\]\$(parse_git_branch)\[\e[0;0m\]$ "

# on any regular directory it will output:
# /path/to/directory$ [PROMPT]

# on a git repository it will output:
# /path/to/directory(branch_name_in_yellow)$ [PROMPT]

Understanding the PS1 components

  • \w inserts the full path to the current directory.
  • \W inserts the name of the current directory.
  • \[ begins a non-printing-character escape sequence.
  • \] ends a non-printing-character escape sequence.
  • \e inserts an escape character, much like \033.
  • \e[X;Y;Zm begins a Bash color sequence whose values style all subsequent characters.
    X selects the effect: 0 resets it, 1 increases brightness, 4 underlines, 5 blinks, 7 swaps the foreground and background, and 8 hides the text.
    Y selects the foreground color: 30 is black, 31 red, 32 green, 33 yellow, 34 blue, 35 magenta, 36 cyan, 37 white, and 39 the default.
    Z selects the background color by adding ten to the corresponding foreground code; for example, 40 is black.
  • \e[0;0m resets the color so that subsequent characters use their previous appearance.
  • \$(function_name) inserts the output of a function call.

The rule

Always wrap color sequences in non-printing-character escape brackets.