SSL certificates expire after a certain period, and once invalid, clients often block access. Monitoring expiration dates ensures timely renewal, preventing service disruptions and maintaining trust.

With cURL’s verbose mode and filters, the server’s certificate details, including the expiration date, can be extracted. Regular checks help maintain continuous secure operations.

By proactively tracking certificate lifecycles, administrators can renew in advance, avoiding downtime, preserving credibility, and ensuring uninterrupted secure communication.

Steps to check SSL certificate expiration using cURL:

  1. Open a terminal.
  2. Request headers and certificate details.
    $ curl --verbose --head --insecure "https://example.com" 2>&1 | grep 'expire date'
    *  expire date: Apr 15 23:59:59 2024 GMT

    --insecure avoids blocking due to invalid certificates.

  3. Note the expiration date and schedule renewals beforehand.

    Prevent warnings and downtime by renewing before expiry.

  4. Automate checks for multiple domains using scripts.
    #!/bin/bash
    sites=("example.com" "another.com")
    for site in "${sites[@]}"; do
      expiration=$(curl --verbose --head --insecure "https://$site" 2>&1 | grep 'expire date' | awk '{print $3,$4,$5,$6,$7}')
      echo "$site: $expiration"
    done

    Automated checks ensure proactive certificate management.

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