S6 Recap: Is Your Site Actually Working?

Session: S6

What You Built

~/scripts/site-check.sh PAGE [PAGE ...] constructs URLs from any supplied page paths using $USER, checks each response, and prints a diagnosis. It does not regenerate the report or publish files automatically.

Three Questions

• DNS: what records, such as addresses, exist for this name? Use host.
• ICMP (Internet Control Message Protocol): carries network diagnostics and errors. Use ping to ask whether echo replies return and how long they take.
• HTTP: what happened when we requested this page? Use curl.

DNS success does not prove a page exists. Failed ping does not prove HTTPS is down. The public ping target is not the classroom server.

On the classroom server, curl can use /etc/hosts to reach local Caddy. Open the pages in your laptop browser too: the script alone does not test public reachability.

Read HTTP

• curl URL: GET, prints the response body.
• curl -i URL: GET, prints headers and body.
• curl -I URL: HEAD, prints headers without a body.
• -L: follow redirects. The lesson’s exact-URL example deliberately does not use it.

With -w '%{http_code}', curl prints 000 when no HTTP response code was received. It is not an HTTP status or an exit code.

Two Decisions

for each page:
  if curl completes successfully:
    if HTTP status is 200: print OK
    elif report is 404: print the report repair
    else: print the actual status and an inspection hint
  else: report a connection failure and read curl's error

$() captures the HTTP status in status. Start each iteration with curl_exit_code=0; || curl_exit_code=$? records a failure. The outer [[ "$curl_exit_code" -eq 0 ]] checks curl’s exit code; the inner [[ "$status" == "200" ]] checks HTTP. A 404 can still give curl exit code 0 because a response arrived.

Keep set -euo pipefail. Handling the failed capture with || lets the script report the error and continue the loop under set -e.

for page in "$@" extends the early page="$1" exercise to all supplied arguments. "" selects the homepage; zero arguments print usage and exit 2. elif tries another condition. The report repair requires both the report filename and 404, using &&.

That describes the lesson example, not a required source layout. Identify each page by URL, path, or homepage/report label and print its HTTP code with a diagnosis, or a clear transport-failure diagnosis. Never call a failed request successful, even if curl printed 200 before exiting nonzero.

Run And Repair

bash -n ~/scripts/site-check.sh
bash ~/scripts/site-check.sh "" maker-report.html
bash ~/scripts/site-check.sh not-a-page.html

Use an unused path for a real 404, without editing statuses or deleting files. That path must not trigger report-regeneration advice. For a missing report, run ~/scripts/maker-report.sh "S5 Report", then build-website, then the checker again.

If the generator is missing, use the provided report script. Your S5 version in ~/src stays untouched.

Each request has a ten-second timeout. Keep certificate verification enabled. This script prints human-readable results; its exit code is not an aggregate health result, and HEAD 200 does not prove the page contents are correct or fresh.

Live Core

You can explain the three network questions, inspect headers and a body, and explain which branch handles an HTTP response versus a command failure. Both real paths return 200, and the pages open in your laptop browser.

Use the diagnostic cases to explain your script’s decisions to another learner. Compare predictions with your actual output. A real 404 is an HTTP response, not a connection failure; do not damage the site to create failures.

Next Session

You already know HTTP statuses, headers, and bodies. In S7, Run Your Own Web Server, start a backend manually, watch requests in its log, match its PID to its listening port, send raw HTTP, and diagnose and recover three safe incidents. Publishing, notes, and Git remain optional practice.

Reinforcement

Repeat the DNS, ping, header, and checker exercises. Explain your actual observations to another learner. No ping reply is valid evidence; do not invent latency.

Optional: repeat the traceroute warm-up to explore hops, or try while to repeat while a condition succeeds. Preserving your script in Git is also optional practice.

Full Autonomy

Use the self-study guide for every stage, the full checker, diagnostic predictions, and recovery steps.