cURL 显示所有时间 DNS解析 TCP连接　总时间

１、curl -w参数

curl -h |grep "write-out"

-w, --write-out <format> Use output FORMAT after completion

2、显示所有时间示例

curl -o /dev/null -s -w "time_namelookup:%{time_namelookup}\ntime_connect: %{time_connect}\ntime_starttransfer: %{time_starttransfer}\ntime_total: %{time_total}\n"  "https://const.net.cn/"

输出:

time_namelookup:0.058759
time_connect: 0.069912
time_starttransfer: 0.147355
time_total: 0.167685

3、参数说明

time_namelookup： DNS 服务器域名解析的时间（以上时间单位都是s）
time_connect： client 发出请求，到 c/s 建立TCP 的时间；里面包括 DNS 解析的时间
time_starttransfer： client 发出请求；到 server 响应发出第一个字节开始的时间；包括前面的2个时间
time_total： 从请求发起到链接关闭的总耗时

4、官方英文说明

time_appconnect:　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_connect: The time, in seconds, it took from the start until the TCP connect to the remote host (or proxy) was completed.
time_namelookup:　The time, in seconds, it took from the start until the name resolving was completed.
time_pretransfer:　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: The time, in seconds, it took for all redirection steps including 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:　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.
time_total:　The total time, in seconds, that the full operation lasted.

5、格式可以使用字符串，格式化文件以及标准输入

The format can　be specified as a literal "string", or you can have　curl read the format from a file with "@filename" and to tell curl to read the format from stdin you write "@-".

6、使用格式文件示例

cat curl-format.txt

   time_namelookup:%{time_namelookup}\n
      time_connect:%{time_connect}\n
   time_appconnect:%{time_appconnect}\n
     time_redirect:%{time_redirect}\n    
  time_pretransfer:%{time_pretransfer}\n  
time_starttransfer:%{time_starttransfer}\n
------------------------------\n
        time_total:  %{time_total}\n

使用示例：

curl -o /dev/null -s -w "@curl-format.txt"  "https://const.net.cn/"

输出结果：

   time_namelookup:0.165160
      time_connect:0.240436
   time_appconnect:0.326137
     time_redirect:0.000000
  time_pretransfer:0.326211
time_starttransfer:0.412927
------------------------------
        time_total:  0.486244

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