https://daniel.haxx.se/blog/2020/03/17/curl-write-out-json/

例子如下：

{
  "url_effective": "https://example.com/",
  "http_code": 200,
  "response_code": 200,
  "http_connect": 0,
  "time_total": 0.44054,
  "time_namelookup": 0.001067,
  "time_connect": 0.11162,
  "time_appconnect": 0.336415,
  "time_pretransfer": 0.336568,
  "time_starttransfer": 0.440361,
  "size_header": 347,
  "size_request": 77,
  "size_download": 1256,
  "size_upload": 0,
  "speed_download": 0.002854,
  "speed_upload": 0,
  "content_type": "text/html; charset=UTF-8",
  "num_connects": 1,
  "time_redirect": 0,
  "num_redirects": 0,
  "ssl_verify_result": 0,
  "proxy_ssl_verify_result": 0,
  "filename_effective": "saved",
  "remote_ip": "93.184.216.34",
  "remote_port": 443,
  "local_ip": "192.168.0.1",
  "local_port": 44832,
  "http_version": "2",
  "scheme": "HTTPS",
  "curl_version": "libcurl/7.69.2 GnuTLS/3.6.12 zlib/1.2.11 brotli/1.0.7 c-ares/1.15.0 libidn2/2.3.0 libpsl/0.21.0 (+libidn2/2.3.0) nghttp2/1.40.0 librtmp/2.3"
}

如果所有 Unix 工具都能这样用 JSON 格式输出信息就好了。