Calculate the total boot time in seconds on a Systemd system

boot-time.sh

#!/bin/sh

# Copyright © 2024 Guiorgy
#
# This program is free software: you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free Software
# Foundation, either version 3 of the License, or (at your option) any later
# version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.
#
# You can see the full GNU General Public License at
# <https://www.gnu.org/licenses/> for more details.

# Extract the total boot time part after the '=' sign of 'systemd-analyze time' output
total_time=$(systemd-analyze time | head -n 1 | awk -F '= ' '{print $2}')

# Function to convert a single time interval ('dd.ddd[m|s|ms|us|ms]') to seconds
convert_interval_to_seconds() {
    interval=$1

    if echo "$interval" | grep -qP '\dy$'; then
        # Years
        years=$(echo "$interval" | grep -oP '\d+(?=y)')
        interval_seconds=$(echo "$years * 60 * 60 * 24 * 365" | bc)
    elif echo "$interval" | grep -qP '\dmonth$'; then
        # Months
        months=$(echo "$interval" | grep -oP '\d+(?=month)')
        interval_seconds=$(echo "$months * 60 * 60 * 24 * 30" | bc)
    elif echo "$interval" | grep -qP '\dw$'; then
        # Weeks
        weeks=$(echo "$interval" | grep -oP '\d+(?=w)')
        interval_seconds=$(echo "$weeks * 60 * 60 * 24 * 7" | bc)
    elif echo "$interval" | grep -qP '\dd$'; then
        # Days
        days=$(echo "$interval" | grep -oP '\d+(?=d)')
        interval_seconds=$(echo "$days * 60 * 60 * 24" | bc)
    elif echo "$interval" | grep -qP '\dh$'; then
        # Hours
        hours=$(echo "$interval" | grep -oP '\d+(?=h)')
        interval_seconds=$(echo "$hours * 60 * 60" | bc)
    elif echo "$interval" | grep -qP '\dmin$'; then
        # Minutes
        minutes=$(echo "$interval" | grep -oP '\d+(?=min)')
        interval_seconds=$(echo "$minutes * 60" | bc)
    elif echo "$interval" | grep -qP '\ds$'; then
        # Seconds
        seconds=$(echo "$interval" | grep -oP '\d+\.\d+|\d+(?=s)')
        interval_seconds=$seconds
    elif echo "$interval" | grep -qP '\dms$'; then
        # Milliseconds
        milliseconds=$(echo "$interval" | grep -oP '\d+\.\d+|\d+(?=ms)')
        interval_seconds=$(echo "$milliseconds / 1000" | bc -l)
    elif echo "$interval" | grep -qP '\dus$'; then
        # Microseconds
        microseconds=$(echo "$interval" | grep -oP '\d+\.\d+|\d+(?=us)')
        interval_seconds=$(echo "$microseconds / 1000000" | bc -l)
    elif echo "$interval" | grep -qP '\dns$'; then
        # Nanoseconds
        nanoseconds=$(echo "$interval" | grep -oP '\d+\.\d+|\d+(?=ns)')
        interval_seconds=$(echo "$nanoseconds / 1000000000" | bc -l)
    else
        # WTF?
        interval_seconds=$interval
    fi

    echo "$interval_seconds"
}

# Initialize total seconds
total_seconds=0

# Split the total_time into intervals and sum them
for interval in $total_time; do
    interval_seconds=$(convert_interval_to_seconds "$interval")
    total_seconds=$(echo "$total_seconds + $interval_seconds" | bc)
done

# Print the total time in seconds without trailing zeroes
echo "$total_seconds" | awk '{printf "%g\n", $0}'