Monitor Website Uptime From the Command Line

Monitor Website Uptime From the Command Line

Uptime monitoring services charge $10-50/month for what amounts to periodic HTTP requests with alerting. If you're monitoring a handful of sites for a side project or small team, you can build the same thing with curl, cron, and free APIs.

Here's how.

The Simplest Monitor

#!/bin/bash
# check-uptime.sh — Monitor a single URL
URL="https://example.com"
STATUS=$(curl -s -o /dev/null -w "%{http_code}" --max-time 10 "$URL")

if [ "$STATUS" != "200" ]; then
  echo "[$(date -u)] $URL returned $STATUS" >> /var/log/uptime.log
  # Send alert (email, Slack webhook, etc.)
fi

Add it to cron:

# Check every 5 minutes
*/5 * * * * /home/user/check-uptime.sh

That's a functional uptime monitor in 8 lines.

Going Further: Visual Verification

HTTP 200 doesn't always mean your site is working. A blank page, a crashed React app, or a database error can all return 200. For visual verification, take a screenshot and check it:

#!/bin/bash
URL="https://myapp.com"

# Get screenshot
curl -s -o /tmp/site-check.png \
  "https://hermesforge.dev/api/screenshot?url=${URL}&width=1280&height=720"

# Check file size — a tiny image likely means a blank/error page
SIZE=$(stat -f%z /tmp/site-check.png 2>/dev/null || stat -c%s /tmp/site-check.png)
if [ "$SIZE" -lt 5000 ]; then
  echo "[$(date -u)] WARNING: $URL screenshot suspiciously small (${SIZE} bytes)" >> /var/log/uptime.log
fi

A real page renders to a reasonably large image. If the screenshot is tiny (under 5KB), something is probably wrong.

Check Multiple Sites

#!/bin/bash
SITES=(
  "https://myapp.com"
  "https://api.myapp.com/health"
  "https://docs.myapp.com"
)

for URL in "${SITES[@]}"; do
  STATUS=$(curl -s -o /dev/null -w "%{http_code}" --max-time 10 "$URL")
  if [ "$STATUS" != "200" ]; then
    echo "[$(date -u)] DOWN: $URL ($STATUS)" >> /var/log/uptime.log
  fi
done

Add Dead Link Checking

Beyond uptime, broken links frustrate users and hurt SEO. Check for dead links on a schedule:

#!/bin/bash
# Weekly dead link scan
RESULT=$(curl -s "https://hermesforge.dev/api/deadlinks?url=https://myapp.com&depth=2")
BROKEN=$(echo "$RESULT" | python3 -c "import sys,json; d=json.load(sys.stdin); print(len(d.get('broken_links',[])))")

if [ "$BROKEN" -gt 0 ]; then
  echo "[$(date -u)] Found $BROKEN broken links on myapp.com" >> /var/log/uptime.log
  echo "$RESULT" >> /var/log/broken-links.json
fi

Check SSL Certificate Expiry

Expired certificates cause downtime that HTTP checks won't catch until it's too late:

#!/bin/bash
# Check SSL expiry for your domains
RESULT=$(curl -s "https://hermesforge.dev/api/ssl?url=https://myapp.com")
DAYS_LEFT=$(echo "$RESULT" | python3 -c "import sys,json; print(json.load(sys.stdin).get('days_until_expiry',0))")

if [ "$DAYS_LEFT" -lt 14 ]; then
  echo "[$(date -u)] SSL cert expires in $DAYS_LEFT days!" >> /var/log/uptime.log
fi

The Full Monitor Script

Combining all of the above into one script that runs every 5 minutes:

#!/bin/bash
# full-monitor.sh
LOG="/var/log/uptime.log"
ALERT_EMAIL="you@example.com"
BASE="https://hermesforge.dev"

SITES=("https://myapp.com" "https://api.myapp.com/health")

for URL in "${SITES[@]}"; do
  STATUS=$(curl -s -o /dev/null -w "%{http_code}" --max-time 10 "$URL")
  if [ "$STATUS" != "200" ]; then
    MSG="[$(date -u)] DOWN: $URL ($STATUS)"
    echo "$MSG" >> "$LOG"
    # Optional: send alert via your preferred method
  fi
done

# Visual check (hourly — don't overdo it)
MINUTE=$(date +%M)
if [ "$MINUTE" = "00" ]; then
  for URL in "${SITES[@]}"; do
    curl -s -o /tmp/check.png "${BASE}/api/screenshot?url=${URL}&width=1280"
    SIZE=$(stat -c%s /tmp/check.png 2>/dev/null || echo 0)
    if [ "$SIZE" -lt 5000 ]; then
      echo "[$(date -u)] VISUAL CHECK FAILED: $URL (${SIZE} bytes)" >> "$LOG"
    fi
  done
fi

Why Not Use a SaaS Monitor?

For production systems with SLAs, use a proper monitoring service — they offer multi-region checks, incident management, and status pages.

But for side projects, staging environments, or personal sites:

For a $0/month side project, a $0/month monitor makes sense.

All the APIs used in this tutorial are free with no signup required. Try them: Screenshot API, Dead Links API, SSL Checker.