Custom bash theme

custom_ps1.bash

# SPDX-License-Identifier: MIT
# Copyright (c) 2025 Siddh Raman Pant <@siddhpant on GitHub>

# Design skeletal inspired from Kali Linux theme PS1: https://superuser.com/a/1781707

# -----------------------------------------------------------------------------


# Check add_starting_line() and add_ending_line()
____custom_ps1_separator="─"

# Colour codes.
____custom_ps1_colour_stop='\[\033[00m\]'
____custom_ps1_bold_yellow_start='\[\033[01;32m\]'  # For separator.
____custom_ps1_bold_blue_start='\[\033[01;34m\]'  # For dir.
____custom_ps1_bold_red_start='\[\033[01;31m\]'  # For shell level.
____custom_ps1_red_start='\[\033[31m\]'    # For command info.
____custom_ps1_green_start='\[\033[32m\]'  # For command info.


# The text in parenthesis and brackets are not joiners. So stop the yellow
# color before the text, and start after the text.

____custom_ps1_left_parenthesis="($____custom_ps1_colour_stop"
____custom_ps1_right_parenthesis="$____custom_ps1_bold_yellow_start)"

____custom_ps1_left_square_bracket="[$____custom_ps1_colour_stop"
____custom_ps1_right_square_bracket="$____custom_ps1_bold_yellow_start]"


# -----------------------------------------------------------------------------


# Save the command start time using PS0, so we can calculate the amount of time
# taken by a command, and also detect whether we actually executed a command or
# just pressed enter / did Ctrl+C / wrote a comment / etc.

____custom_ps1_previous_command_start_time=''

# Use parameter substitution trick to assign the value to our variable.
# We cannot use a simple function as that will execute in a subshell.
____custom_ps1_start_time_assigner='${____custom_ps1_previous_command_start_time:=${EPOCHREALTIME/[^0-9]/}}'

# Since the above results in a string, but we don't want it to be printed,
# let's use the replace parameter substitution trick on the same variable so
# that the assignment happens, but the initial empty string stays empty.
PS0='${____custom_ps1_previous_command_start_time//?/'
PS0+=$____custom_ps1_start_time_assigner
PS0+='}'

# -----------------------------------------------------------------------------


____custom_ps1_format_duration_us()
{
	local us=$1
	local day=$(( us / 86400000000 ))
	local hr=$((  us / 3600000000 % 24 ))
	local min=$(( us / 60000000 % 60 ))
	local sec=$(( us / 1000000 % 60 ))
	local ms=$((  us / 1000 % 1000))

	local formatted_duration=""

	if (( $day != 0 )); then formatted_duration+="${day}d "; fi
	if (( $hr != 0 )); then formatted_duration+="${hr}h "; fi
	if (( $min != 0 )); then formatted_duration+="${min}m "; fi

	if [[ "$formatted_duration" == "" ]] && [[ "$sec" == "0" ]] ; then
		formatted_duration+="${ms}ms"
	else
		printf -v ms "%03d" $ms
		formatted_duration+="${sec}.${ms}s"
	fi

	echo $formatted_duration
}


____custom_ps1_exit_code_to_str()
{
	local exit_code_int=$1
	local exit_code_str="$exit_code_int"

	case $exit_code_int in
		1) exit_code_str="ERROR";;
		2) exit_code_str="USAGE";;

		64) exit_code_str="USAGE";;
		65) exit_code_str="DATAERR";;
		66) exit_code_str="NOINPUT";;
		67) exit_code_str="NOUSER";;
		68) exit_code_str="NOHOST";;
		69) exit_code_str="UNAVAILABLE";;
		70) exit_code_str="SOFTWARE";;
		71) exit_code_str="OSERR";;
		72) exit_code_str="OSFILE";;
		73) exit_code_str="CANTCREAT";;
		74) exit_code_str="IOERR";;
		75) exit_code_str="TEMPFAIL";;
		76) exit_code_str="PROTOCOL";;
		77) exit_code_str="NOPERM";;
		78) exit_code_str="CONFIG";;

		126) exit_code_str="NOPERM";;
		127) exit_code_str="NOTFOUND";;

		# From output of `kill -l`, with codes 128 + n.
		129) exit_code_str="SIGHUP";;
		130) exit_code_str="SIGINT";;
		131) exit_code_str="SIGQUIT";;
		132) exit_code_str="SIGILL";;
		133) exit_code_str="SIGTRAP";;
		134) exit_code_str="SIGABRT";;
		135) exit_code_str="SIGBUS";;
		136) exit_code_str="SIGFPE";;
		137) exit_code_str="SIGKILL";;
		138) exit_code_str="SIGUSR1";;
		139) exit_code_str="SIGSEGV";;
		140) exit_code_str="SIGUSR2";;
		141) exit_code_str="SIGPIPE";;
		142) exit_code_str="SIGALRM";;
		143) exit_code_str="SIGTERM";;
		144) exit_code_str="SIGSTKFLT";;
		145) exit_code_str="SIGCHLD";;
		146) exit_code_str="SIGCONT";;
		147) exit_code_str="SIGSTOP";;
		148) exit_code_str="SIGTSTP";;
		149) exit_code_str="SIGTTIN";;
		150) exit_code_str="SIGTTOU";;
		151) exit_code_str="SIGURG";;
		152) exit_code_str="SIGXCPU";;
		153) exit_code_str="SIGXFSZ";;
		154) exit_code_str="SIGVTALRM";;
		155) exit_code_str="SIGPROF";;
		156) exit_code_str="SIGWINCH";;
		157) exit_code_str="SIGIO";;
		158) exit_code_str="SIGPWR";;
		159) exit_code_str="SIGSYS";;
		162) exit_code_str="SIGRTMIN";;
		163) exit_code_str="SIGRTMIN+1";;
		164) exit_code_str="SIGRTMIN+2";;
		165) exit_code_str="SIGRTMIN+3";;
		166) exit_code_str="SIGRTMIN+4";;
		167) exit_code_str="SIGRTMIN+5";;
		168) exit_code_str="SIGRTMIN+6";;
		169) exit_code_str="SIGRTMIN+7";;
		170) exit_code_str="SIGRTMIN+8";;
		171) exit_code_str="SIGRTMIN+9";;
		172) exit_code_str="SIGRTMIN+10";;
		173) exit_code_str="SIGRTMIN+11";;
		174) exit_code_str="SIGRTMIN+12";;
		175) exit_code_str="SIGRTMIN+13";;
		176) exit_code_str="SIGRTMIN+14";;
		177) exit_code_str="SIGRTMIN+15";;
		178) exit_code_str="SIGRTMAX-14";;
		179) exit_code_str="SIGRTMAX-13";;
		180) exit_code_str="SIGRTMAX-12";;
		181) exit_code_str="SIGRTMAX-11";;
		182) exit_code_str="SIGRTMAX-10";;
		183) exit_code_str="SIGRTMAX-9";;
		184) exit_code_str="SIGRTMAX-8";;
		185) exit_code_str="SIGRTMAX-7";;
		186) exit_code_str="SIGRTMAX-6";;
		187) exit_code_str="SIGRTMAX-5";;
		188) exit_code_str="SIGRTMAX-4";;
		189) exit_code_str="SIGRTMAX-3";;
		190) exit_code_str="SIGRTMAX-2";;
		191) exit_code_str="SIGRTMAX-1";;
		192) exit_code_str="SIGRTMAX";;
	esac

	echo $exit_code_str
}


# -----------------------------------------------------------------------------


# Initialise PS1 here so we can set it in functions later.
# This is the only place where it will be an empty string.
# So it will be empty only before the first prompt of the terminal window.
PS1=''
____custom_ps1_previous_command_exit_status=''


____custom_ps1_show_previous_command_info()
{
	____custom_ps1_previous_command_exit_status=$?

	# First prompt of terminal doesn't need to account for last command.
	if [[ "$PS1" == '' ]] && (( $SHLVL == 1 )); then
		return
	fi

	# We don't need to account for "previous" command if the last prompt
	# had no command execution. In that case, there will be no PS0 and thus
	# no previous_command_start_time.
	if [[ $____custom_ps1_previous_command_start_time == '' ]]; then
		# Add a newline regardless.
		PS1="\n"
		return
	fi

	# Save previous info in local variables for better naming.
	local previous_start_time=$____custom_ps1_previous_command_start_time
	local previous_exit_status=$(
		____custom_ps1_exit_code_to_str \
			$____custom_ps1_previous_command_exit_status
	)

	# Reset global variables now itself.
	PS1=''
	____custom_ps1_previous_command_start_time=''

	# If the last command didn't end with a newline (like a printf), then
	# our right prompt for info will get messed up. So in that case, we
	# will add a new line and just make it explicit like GitHub that there
	# is no newline using a symbol.
	local row_pos
	local col_pos
	local newline_start=" "

	# https://unix.stackexchange.com/a/183121
	IFS=';' read -sdR -p $'\E[6n' row_pos col_pos

	if [[ "${col_pos#*[}" != "1" ]]; then
		# In the above check, we stripped escape codes from col_pos.
		PS1+="\n"
		newline_start=$____custom_ps1_bold_red_start
		newline_start+="⊖"
		newline_start+=$____custom_ps1_colour_stop
	fi

	local current_time=${EPOCHREALTIME/[^0-9]/}
	local runtime_us=$(( current_time - previous_start_time	))

	local time_taken_str=$(____custom_ps1_format_duration_us $runtime_us)

	local info=""
	local info_colour=""

	if [[ "$previous_exit_status" == "0" ]]; then
		info_colour=$____custom_ps1_green_start
		info="[$time_taken_str]"
	else
		info_colour=$____custom_ps1_red_start
		info="[$previous_exit_status / $time_taken_str]"
	fi

	# Right align info (acounting for extra char we will add later).
	printf -v info "%$(( $COLUMNS - 1 ))s" "$info"

	PS1+=$newline_start
	PS1+=$info_colour
	PS1+=$info
	PS1+=$____custom_ps1_colour_stop
	PS1+="\n"
}


____custom_ps1_add_starting_line()
{
	PS1+=$____custom_ps1_bold_yellow_start
	PS1+='┌──'
	PS1+='${debian_chroot:+($debian_chroot)}'
}


____custom_ps1_add_ending_line()
{
	PS1+='\n'
	PS1+='└─'
	PS1+=$____custom_ps1_colour_stop
	PS1+='\$ '  # \$ is an escape sequence for PS1 (# if UID 0, else $).
}


____custom_ps1_add_shell_level()
{
	if (( $SHLVL == 1 )); then
		return
	fi

	PS1+=$____custom_ps1_separator

	PS1+=$____custom_ps1_left_parenthesis
	PS1+=$____custom_ps1_bold_red_start
	PS1+=" Lvl $SHLVL"
	PS1+=$____custom_ps1_colour_stop
	PS1+=$____custom_ps1_right_parenthesis
}


____custom_ps1_add_pwd()
{
	PS1+=$____custom_ps1_separator

	PS1+=$____custom_ps1_left_square_bracket
	PS1+=$____custom_ps1_bold_blue_start
	PS1+='\w'
	PS1+=$____custom_ps1_colour_stop
	PS1+=$____custom_ps1_right_square_bracket
}


____custom_ps1_add_git()
{
	____custom_ps1_git_ps1="$(
		GIT_PS1_SHOWDIRTYSTATE=1
		GIT_PS1_SHOWSTASHSTATE=1
		GIT_PS1_SHOWCONFLICTSTATE=1
		GIT_PS1_SHOWUNTRACKEDFILES=1
		GIT_PS1_SHOWUPSTREAM="verbose"
		GIT_PS1_DESCRIBE_STYLE=default
		__git_ps1
	)"

	if [[ "$____custom_ps1_git_ps1" == "" ]]; then
		return
	fi

	# Remove starting space and parentheses.
	____custom_ps1_git_ps1=${____custom_ps1_git_ps1:2:-1}

	PS1+=$____custom_ps1_separator

	PS1+=$____custom_ps1_left_square_bracket
	PS1+=$____custom_ps1_git_ps1
	PS1+=$____custom_ps1_right_square_bracket
}

____custom_ps1_build_ps1()
{
	____custom_ps1_show_previous_command_info
	____custom_ps1_add_starting_line
	____custom_ps1_add_shell_level
	____custom_ps1_add_pwd
	____custom_ps1_add_git
	____custom_ps1_add_ending_line
}

PROMPT_COMMAND="____custom_ps1_build_ps1"