Convert seconds past datetime to datetime

gistfile1.txt

#!/bin/bash

# Function to calculate datetime after a given number of seconds from a starting datetime
calculate_datetime() {
    local start_datetime="$1"
    local elapsed_seconds="$2"

    # Convert the start datetime to seconds since the epoch
    local start_epoch=$(date -d "$start_datetime" +%s)

    # Add the elapsed seconds (including fractional part)
    local result_epoch=$(echo "$start_epoch + $elapsed_seconds" | bc)

    # Convert the result back to a human-readable date-time format (without fractional seconds)
    local result_datetime=$(date -d "@$result_epoch" +"%Y-%m-%d %H:%M:%S")

    # Output the resulting datetime
    echo "$result_datetime"
}

# Example usage of the function
# Uncomment the lines below to test the function directly in the script
#start_datetime="2024-08-12 08:00:00"
#elapsed_seconds="45736.799"
#result=$(calculate_datetime "$start_datetime" "$elapsed_seconds")
#echo "The resulting datetime is: $result"

process_log_file.sh

#!/bin/bash

# Function to calculate datetime after a given number of seconds from a starting datetime
calculate_datetime() {
    local start_datetime="$1"
    local elapsed_seconds="$2"

    # Convert the start datetime to seconds since the epoch
    local start_epoch=$(date -d "$start_datetime" +%s)

    # Add the elapsed seconds (including fractional part)
    local result_epoch=$(echo "$start_epoch + $elapsed_seconds" | bc)

    # Convert the result back to a human-readable date-time format (without fractional seconds)
    local result_datetime=$(date -d "@$result_epoch" +"%Y-%m-%d %H:%M:%S")

    # Output the resulting datetime
    echo "$result_datetime"
}

# Check if the correct number of arguments is provided
if [ $# -ne 2 ]; then
    echo "Usage: $0 <log_file> <initial_datetime>"
    echo "Example: $0 /path/to/log_file.txt '2024-08-12 08:00:00'"
    exit 1
fi

# Assign arguments to variables
log_file="$1"
initial_datetime="$2"

# Check if the log file exists
if [ ! -f "$log_file" ]; then
    echo "Error: Log file not found!"
    exit 1
fi

# Process each line in the log file
while IFS= read -r log_line; do
    # Extract the time value (e.g., 12.592) from the log line using a regular expression
    elapsed_seconds=$(echo "$log_line" | grep -oP '\[\s*\K[\d\.]+')

    # If a valid elapsed time is found, calculate the corresponding datetime
    if [ ! -z "$elapsed_seconds" ]; then
        datetime=$(calculate_datetime "$initial_datetime" "$elapsed_seconds")

        # Replace the time value in the log line with the calculated datetime
        new_log_line=$(echo "$log_line" | sed "s/\[\s*$elapsed_seconds\]/[$datetime]/")

        # Output the modified log line
        echo "$new_log_line"
    else
        # If no time value is found, print the line as is
        echo "$log_line"
    fi
done < "$log_file"

Here's how to use it:

chmod +x process_log_file.sh

./process_log_file.sh /path/to/your_log_file.txt '2024-08-12 08:00:00'

curl https://gist.githubusercontent.com/meetnick/eccc5dfea67a6baa2300cb4853e575d6/raw/e70f1dc5525c5f0cb56144e52ce3ab9750aeb65a/process_log_file.sh | bash -s /var/log/Xorg.0.log "2024-08-07 11:44:32"