prepare-hosts

#!/bin/bash
WIN_HOSTS="/mnt/c/Windows/System32/drivers/etc/hosts"
TMP_HOSTS="/tmp/prepare-hosts"
WIN_IP=$(grep </etc/resolv.conf 'nameserver' | cut -f 2 -d ' ')
WSL_IP=$(ip addr show eth0 | grep 'inet ' | cut -f 6 -d ' ' | cut -f 1 -d '/')

export WIN_IP
export WSL_IP

check_ip() {
  IP_NAME=$1
  IP=$2

  if [[ "$IP" == "" ]]; then
    printf "%s: \x1b[31mIP is empty!\x1b[0m\n" "$IP_NAME"
  else
    printf "%s: \x1b[32m%s\x1b[0m\n" "$IP_NAME" "$IP"
  fi
}

prepare_hosts() {
  HOSTS_FILE=$1
  TMP_HOSTS_FILE=$2
  MARK=$3
  IP=$4

  if [[ "$IP" != "" ]]; then
    if grep -q "[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\s\{1,\}$MARK" "$HOSTS_FILE"; then
      printf "\x1b[32mFound %s marks!\x1b[0m\n" "$MARK"
      rm -f "$TMP_HOSTS_FILE"
      cp "$HOSTS_FILE" "$TMP_HOSTS_FILE"
      sed -i -e "s/[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\(\s\{1,\}\)$MARK/$IP\1$MARK/g" "$TMP_HOSTS_FILE"
      sed -i -e "s/[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\(\s\{1,\}\)\(.*\)\(\s\{1,\}\)#$MARK/$IP\1\2\3#$MARK/g" "$TMP_HOSTS_FILE"
      cat "$TMP_HOSTS_FILE" >"$HOSTS_FILE"
    else
      printf "%s %s\n" "$IP" "$MARK" >>"$HOSTS_FILE"
    fi
  fi

}

check_ip "Windows IP" "$WIN_IP"
check_ip "WSL IP" "$WSL_IP"

prepare_hosts $WIN_HOSTS $TMP_HOSTS "wsl2" "$WSL_IP"
prepare_hosts $WIN_HOSTS $TMP_HOSTS "winhost" "$WIN_IP"

printf "\nNew hosts file: \n\n"
printf "\x1b[34m=====================================================================\x1b[0m\n"
cat "$WIN_HOSTS"
printf "\x1b[34m=====================================================================\x1b[0m\n"
rm -f "$TMP_HOSTS"
printf "\n\x1b[32mDONE!\x1b[0m\n\n"