Bash Function to_timestamp_ms – Convert Dates to Unix Timestamp in Milliseconds

to_timestamp_ms.sh

#!/bin/bash
# File: to_timestamp_ms.sh
# Description: Convert a date in DD/MM/YYYY HH:MM:SS format to Unix timestamp in milliseconds
# Compatible with macOS (BSD date) and Linux (GNU date)
# 
# Example usage:
#   ./to_timestamp_ms.sh "25/08/2025 19:50:05"
#   # Output: 1756162205000
# 
# Or source the script and use the function directly in your shell:
#   source to_timestamp_ms.sh
#   to_timestamp_ms "25/08/2025 19:50:05"

to_timestamp_ms() {
  local input="$*"
  if command -v gdate >/dev/null 2>&1; then
    gdate -d "$input" "+%s%3N"
  elif date --version >/dev/null 2>&1; then
    date -d "$input" "+%s%3N"
  else
    date -j -f "%d/%m/%Y %H:%M:%S" "$input" "+%s000"
  fi
}