# Step 3 — Multiple URLs + Sampling

## What this step delivers

- Multiple URLs accepted as positional arguments; each is measured in turn.
- `-n`/`--count` flag repeats each URL N times and reports **min / avg / max**
  per phase instead of a single value.
- With `n=1` (the default) the output is identical to Step 2.

## Build

```sh
cd go
go build -o latprobe .
```

## Usage

```sh
latprobe [flags] <url> [url ...]

  -n, --count int   Number of requests per URL (default 1)
```

## Examples

### Default (single sample, unchanged from Step 2)

```sh
$ ./latprobe https://example.com
https://example.com  (200)
  DNS lookup     :     13.74 ms
  TCP connect    :     11.20 ms
  TLS handshake  :     22.92 ms
  Server (TTFB)  :     14.88 ms
  Transfer       :      0.11 ms
  ─────────────────────────────
  Total          :     63.97 ms
```

### Multiple samples (`-n`)

```sh
$ ./latprobe -n 5 https://example.com
https://example.com  (200, 5 samples)
                          min        avg        max
  DNS lookup     :    1.50 ms    1.60 ms    1.70 ms
  TCP connect    :   10.20 ms   10.80 ms   11.50 ms
  TLS handshake  :   21.00 ms   22.10 ms   23.40 ms
  Server (TTFB)  :   12.00 ms   13.50 ms   15.20 ms
  Transfer       :    0.07 ms    0.09 ms    0.12 ms
  ─────────────────────────────────────────────────
  Total          :   45.00 ms   48.10 ms   52.00 ms
```

### Multiple URLs

```sh
$ ./latprobe -n 3 https://example.com https://www.google.com
https://example.com  (200, 3 samples)
                          min        avg        max
  ...
  ─────────────────────────────────────────────────
  Total          :   ...

https://www.google.com  (200, 3 samples)
                          min        avg        max
  ...
```

## Notes

- **DNS and connect on repeated requests**: after the first request the OS
  DNS cache and HTTP keep-alive may eliminate those phases in subsequent
  samples. The spread in TCP connect and DNS between min and max shows the
  true variance when caches are cold.
- **Partial failure**: if a sample fails mid-run, that URL is skipped and
  the exit code is 1. Successful samples already collected are discarded for
  that URL.