My bash prompt

Background

this page is more a resource for me to have a place i can come back to if i wanted to customize my bash prompt.

the knowledge section is a reference for the things i’ve learnt about customizing the bash prompt, and the my prompt section describes my prompt.

Knowledge

The basic structure of an ANSI escape code is:
\e[<Attribute>;<ForegroundColor>;<BackgroundColor>m
or
\033[<Attribute>;<ForegroundColor>;<BackgroundColor>m

<Attribute> values: | Code | Effect | | :— | :——– | | 0 | Reset | | 1 | Bold | | 4 | Underline |

ESC[38;5;{ID}m Set foreground color.
ESC[48;5;{ID}m Set background color.

<ForegroundColor>;<BackgroundColor> values: | Color Name | Foreground Color Code | Background Color Code | | —————- | ——————— | ——————— | | Black | 30 | 40 | | Black (bright) | 90 | 100 | | Blue | 34 | 44 | | Blue (bright) | 94 | 104 | | Cyan | 36 | 46 | | Cyan (bright) | 96 | 106 | | Green | 32 | 42 | | Green (bright) | 92 | 102 | | Magenta | 35 | 45 | | Magenta (bright) | 95 | 105 | | Red | 31 | 41 | | Red (bright) | 91 | 101 | | White | 37 | 47 | | White (bright) | 97 | 107 | | Yellow | 33 | 43 | | Yellow (bright) | 93 | 103 | | Reset | 0 | 0 | | Default | 39 | 49 |

\u: The username of the current user.
\h: The hostname of the system, up to the first dot.
\H: The full hostname.
\w: The current working directory, with the home directory abbreviated to ~.
\W: The basename of the current working directory.
\$: The prompt symbol ($ for a regular user, # for the root user).
\d: The current date.
\t: The current time in 24-hour HH:MM:SS format.
\A: The current time in 24-hour HH:MM format.
\e: An escape character, used in conjunction with ANSI escape sequences for terminal control (e.g., color changes).
\[ and \]: Markers for non-printable characters (like color codes) to ensure proper cursor positioning by readline.
\!: The history number of the current command.
\v: The version of Bash.

My prompt

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# Format: \e[<Attribute>;<ForegroundColor>;<BackgroundColor>m

# --- Attribute Variables ---
# Text Attributes
ATTR_RESET="0" # RESETs all attributes
ATTR_BOLD="1"  # Bold text

# --- Color Variables ---
# Foreground Colors
FG_BLACK="30"
FG_BLACK_BRGHT="90"
FG_BLUE="34"
FG_BLUE_BRGHT="94"
FG_CYAN="36"
FG_CYAN_BRGHT="96"
FG_GREEN="32"
FG_GREEN_BRGHT="92"
FG_MAGENTA="35"
FG_MAGENTA_BRGHT="95"
FG_RED="31"
FG_RED_BRGHT="91"
FG_WHITE="37"
FG_WHITE_BRGHT="97"
FG_YELLOW="33"
FG_YELLOW_BRGHT="93"
FG_RESET="0"
FG_DEFAULT="39"

# Background Colors
BG_BLACK="40"
BG_BLACK_BRGHT="100"
BG_BLUE="44"
BG_BLUE_BRGHT="104"
BG_CYAN="46"
BG_CYAN_BRGHT="106"
BG_GREEN="42"
BG_GREEN_BRGHT="102"
BG_MAGENTA="45"
BG_MAGENTA_BRGHT="105"
BG_RED="41"
BG_RED_BRGHT="101"
BG_WHITE="47"
BG_WHITE_BRGHT="107"
BG_YELLOW="43"
BG_YELLOW_BRGHT="103"
BG_RESET="0"
BG_DEFAULT="49"

# --- Prompt Sections ---
# Define colors for different parts of the prompt.
# Change these to quickly theme your prompt.
COLOR_USER_BG=$BG_RED
COLOR_USER_FG=$FG_BRIGHT_WHITE

COLOR_DIR_BG=$BG_BLACK
COLOR_DIR_FG=$FG_RED

COLOR_NONE_BG=$BG_DEFAULT
COLOR_USER_SEP_FG=$FG_RED
COLOR_DIR_SEP_FG=$FG_BLACK

# --- Prompt Symbols ---
# Powerline symbols for a modern look.
SEPARATOR_R="" # Separator pointing right
SEPARATOR_L="" # Separator pointing left

# --- Directory Truncation Function ---
# Truncates the current working directory to a specified length.
prompt_dir() {
  local dir_path="${PWD/$HOME/\~}" # Replace home with ~
  local max_len=35                 # Max length of the path

  if [ ${#dir_path} -gt $max_len ]; then
    # Truncate by showing the first directory and the last two.
    local truncated_path=$(echo "$dir_path" | awk -F'/' '{
      if (NF>3) {
        print $1 "/.../" $(NF-1) "/" $NF
      } else {
        print $0
      }
    }')
    echo "$truncated_path"
  else
    echo "$dir_path"
  fi
}

# --- PROMPT_COMMAND ---
# This command is executed before the prompt is displayed.
PROMPT_COMMAND='short_pwd="$(prompt_dir)"'

# --- PS1 Prompt String ---
# Build the prompt using the color variables.

# Start of the prompt
PS1="\[\e[${ATTR_RESET};${COLOR_USER_SEP_FG};${COLOR_NONE_BG}m\]${SEPARATOR_L}"
PS1+="\[\e[${ATTR_BOLD};${COLOR_USER_FG};${COLOR_USER_BG}m\]"

# User section
PS1+="\u" # \u is the username

# Separator between user and directory
PS1+="\[\e[${ATTR_RESET};${COLOR_USER_SEP_FG};${COLOR_DIR_BG}m\]${SEPARATOR_R}"

# Directory section
PS1+="\[\e[${ATTR_RESET};${COLOR_DIR_FG};${COLOR_DIR_BG}m\]"
PS1+=" \$short_pwd" # The truncated directory path

# Final separator
PS1+="\[\e[${ATTR_RESET};${COLOR_DIR_SEP_FG};${BG_DEFAULT}m\]${SEPARATOR_R}"

# RESET colors and add the final prompt character
PS1+="\[\e[${ATTR_RESET}m\]\$ "