如何通过curl命令调用某个请求，并且只返回请求的http状态码？

通过如下的命令来实现这个目的：

curl -s -w "%{http_code}\n" -o /dev/null 172.23.4.18:8888/healthcheck

执行结果：

[root@nccztsjb-node-14 ~]# curl -s -w "%{http_code}\n" -o /dev/null 172.23.4.18:8888/healthcheck
200

这样，就只返回了请求的状态码。

-w 引用变量的方法：-w "%{http_code}"

参数解释

• -s : 只显示返回结果
• -o: /dev/null 将输出定向到/dev/null设备
• -w: 输出要显示的内容

-w的作用及相关变量如下：

1. url_effective 最终获取的url地址，尤其是当你指定给curl的地址存在301跳转，且通过-L继续追踪的情形。
2. http_code http状态码，如200成功,301转向,404未找到,500服务器错误等。(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.)
3. 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)
4. time_total 总时间，按秒计。精确到小数点后三位。 （The total time, in seconds, that the full operation lasted. The time will be displayed with millisecond resolution.）
5. time_namelookup DNS解析时间,从请求开始到DNS解析完毕所用时间。(The time, in seconds, it took from the start until the name resolving was completed.)
6. time_connect 连接时间,从开始到建立TCP连接完成所用时间,包括前边DNS解析时间，如果需要单纯的得到连接时间，用这个time_connect时间减去前边time_namelookup时间。以下同理，不再赘述。(The time, in seconds, it took from the start until the TCP connect to the remote host (or proxy) was completed.)
7. time_appconnect 连接建立完成时间，如SSL/SSH等建立连接或者完成三次握手时间。(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))
8. time_pretransfer 从开始到准备传输的时间。(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.)
9. time_redirect 重定向时间，包括到最后一次传输前的几次重定向的DNS解析，连接，预传输，传输时间。(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))
10. time_starttransfer 开始传输时间。在发出请求之后，Web 服务器返回数据的第一个字节所用的时间(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.)
11. size_download 下载大小。(The total amount of bytes that were downloaded.)
12. size_upload 上传大小。(The total amount of bytes that were uploaded.)
13. size_header 下载的header的大小(The total amount of bytes of the downloaded headers.)
14. size_request 请求的大小。(The total amount of bytes that were sent in the HTTP request.)
15. speed_download 下载速度，单位-字节每秒。(The average download speed that curl measured for the complete download. Bytes per second.)
16. speed_upload 上传速度,单位-字节每秒。(The average upload speed that curl measured for the complete upload. Bytes per second.)
17. content_type 就是content-Type，不用多说了，这是一个访问我博客首页返回的结果示例(text/html; charset=UTF-8)；(The Content-Type of the requested document, if there was any.)
18. num_connects 最近的的一次传输中创建的连接数目。Number of new connects made in the recent transfer. (Added in 7.12.3)
19. num_redirects 在请求中跳转的次数。Number of redirects that were followed in the request. (Added in 7.12.3)
20. 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)
21. ftp_entry_path 当连接到远程的ftp服务器时的初始路径。The initial path libcurl ended up in when logging on to the remote FTP server. (Added in 7.15.4)
22. ssl_verify_result ssl认证结果，返回0表示认证成功。( The result of the SSL peer certificate verification that was requested. 0 means the verification was successful. (Added in 7.19.0))