Write a shell script that adds...

Here's an example shell script that adds, updates, or deletes DNS records to the NSD service based on an input CSV file:

#!/bin/bash

# Set variables
CSV_FILE="/path/to/csv/file"
ZONE_NAME="example.com"
NSD_CONTROL="/usr/sbin/nsd-control"

# Get list of current DNS records from NSD
NSD_ZONE=$($NSD_CONTROL dumpzone $ZONE_NAME)

# Loop through CSV file
while IFS=, read -r RECORD_NAME RECORD_TYPE RECORD_VALUE; do

  # Check if record exists in NSD zone
  if [[ "$NSD_ZONE" =~ (^|[[:space:]])"$RECORD_NAME[[:space:]]+([[:digit:]]+)[[:space:]]+IN[[:space:]]+$RECORD_TYPE[[:space:]]+$RECORD_VALUE($|[[:space:]])" ]]; then

    # Update existing record
    $NSD_CONTROL editzone $ZONE_NAME update $RECORD_NAME $RECORD_TYPE $RECORD_VALUE

  else

    # Add new record
    $NSD_CONTROL editzone $ZONE_NAME add $RECORD_NAME $RECORD_TYPE $RECORD_VALUE

  fi

done < "$CSV_FILE"

# Delete records that are not in the CSV file
for RECORD_NAME in $(grep -oP '(?<=\A)[^,]+' $CSV_FILE); do

  if [[ ! "$NSD_ZONE" =~ (^|[[:space:]])"$RECORD_NAME[[:space:]]+([[:digit:]]+)[[:space:]]+IN[[:space:]]+[[:upper:]]+($|[[:space:]])" ]]; then

    # Delete record
    $NSD_CONTROL editzone $ZONE_NAME del $RECORD_NAME

  fi

done

Here is how to use the script:

1. Replace the CSV_FILE variable with the path to your input CSV file.
2. Replace the ZONE_NAME variable with the name of your DNS zone.
3. Replace the NSD_CONTROL variable with the path to your nsd-control binary.
4. Set execute permission for the script: chmod +x /path/to/script.sh
5. Run the script: /path/to/script.sh

The script will loop through each line of the CSV file and determine whether to add, update, or delete DNS records based on the comparison with the current DNS records in NSD. The script will add new records, update existing records, and delete records that are not in the CSV file.