通過CURL命令可以方便的查詢各種http請求的問題，-w參數對於我們診斷問題非常重要，以下是-w參數對應的一些變量以及對應的解釋：
- url_effective 最終獲取的url地址，尤其是當你指定給curl的地址存在301跳轉，且通過-L繼續追蹤的情形。
- http_code http狀態碼，如200成功,301轉向,404未找到,500服務器錯誤等。(The numerical response code that was found in the last retrieved HTTP(S) or FTP(s) transfer. In 7.18.2 the alias response_code was added to show the same info.)
- http_connect The numerical code that was found in the last response (from a proxy) to a curl CONNECT request. (Added in 7.12.4)
- time_total 總時間，按秒計。精確到小數點後三位。 （The total time, in seconds, that the full operation lasted. The time will be displayed with millisecond resolution.）
- time_namelookup DNS解析時間,從請求開始到DNS解析完畢所用時間。(The time, in seconds, it took from the start until the name resolving was completed.)
- time_connect 連接時間,從開始到建立TCP連接完成所用時間,包括前邊DNS解析時間，如果需要單純的得到連接時間，用這個time_connect時間減去前邊time_namelookup時間。以下同理，不再贅述。(The time, in seconds, it took from the start until the TCP connect to the remote host (or proxy) was completed.)
- time_appconnect 連接建立完成時間，如SSL/SSH等建立連接或者完成三次握手時間。(The time, in seconds, it took from the start until the SSL/SSH/etc connect/handshake to the remote host was completed. (Added in 7.19.0))
- time_pretransfer 從開始到準備傳輸的時間。(The time, in seconds, it took from the start until the file transfer was just about to begin. This includes all pre-transfer commands and negotiations that are specific to the particular protocol(s) involved.)
- time_redirect 重定向時間，包括到最後一次傳輸前的幾次重定向的DNS解析，連接，預傳輸，傳輸時間。(The time, in seconds, it took for all redirection steps include name lookup, connect, pretransfer and transfer before the final transaction was started. time_redirect shows the complete execution time for multiple redirections. (Added in 7.12.3))
- time_starttransfer 開始傳輸時間。在發出請求之後，Web 服務器返回數據的第一個字節所用的時間(The time, in seconds, it took from the start until the first byte was just about to be transferred. This includes time_pretransfer and also the time the server needed to calculate the result.)
- size_download 下載大小。(The total amount of bytes that were downloaded.)
- size_upload 上傳大小。(The total amount of bytes that were uploaded.)size_header 下載的header的大小(The total amount of bytes of the downloaded headers.)
- size_request 請求的大小。(The total amount of bytes that were sent in the HTTP request.)
- speed_download 下載速度，單位-字節每秒。(The average download speed that curl measured for the complete download. Bytes per second.)
- speed_upload 上傳速度,單位-字節每秒。(The average upload speed that curl measured for the complete upload. Bytes per second.)
- content_type 就是content-Type，不用多說了，這是一個訪問我博客首頁返回的結果示例(text/html; charset=UTF-8)；(The Content-Type of the requested document, if there was any.)
- num_connects 最近的的一次傳輸中創建的連接數目。Number of new connects made in the recent transfer. (Added in 7.12.3)
- num_redirects 在請求中跳轉的次數。Number of redirects that were followed in the request. (Added in 7.12.3)
- redirect_url When a HTTP request was made without -L to follow redirects, this variable will show the actual URL a redirect would take you to. (Added in 7.18.2)
- ftp_entry_path 當連接到遠程的ftp服務器時的初始路徑。The initial path libcurl ended up in when logging on to the remote FTP server. (Added in 7.15.4)
- ssl_verify_result ssl認證結果，返回0表示認證成功。( The result of the SSL peer certificate verification that was requested. 0 means the verification was successful. (Added in 7.19.0))
使用案例
以下是使用curl診斷服務器到微信api服務器的網絡訪問情況
curl -o /dev/null -s -w "time_connect: %{time_connect}\ntime_starttransfer: %{time_starttransfer}\ntime_nslookup:%{time_namelookup}\ntime_total: %{time_total}\n" "https://api.weixin.qq.com"
1
結果如下：
time_connect: 0.154
time_starttransfer: 0.243
time_nslookup:0.150
time_total: 0.243
說明: 以上顯示網絡連接時間爲0.154秒（其中DNS解析爲0.150秒），總體請求0.243秒。DNS解析出現故障的概率在正式環境中比較高，所以在診斷時候千萬別漏了time_namelookup這個參數。
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版權聲明：本文爲CSDN博主「weifangan」的原創文章，遵循CC 4.0 BY-SA版權協議，轉載請附上原文出處鏈接及本聲明。
原文鏈接：https://blog.csdn.net/weifangan/article/details/80741981