curl brief introduction

curl Is an open source command line tool , It is based on network protocol , Specify URL Network transmission , After getting the data, there is no specific processing （ Such as ：html And so on ）, Display directly in " standard output "（stdout） On .

curl There are many supported network protocols , Include ：DICT、FILE、FTP、FTPS、GOPHER、GOPHERS、HTTP、HTTPS、IMAP、IMAPS、LDAP、LDAPS、MQTT、POP3、POP3S、RTMP、RTMPS、RTSP、SCP、SFTP、SMB、SMBS、SMTP、SMTPS、TELNET and TFTP.

curl There are also many parameters , Here are some common parameters , It is recommended to save .

send out GET request

When curl Without any parameters ,curl Default issue GET request , The content returned by the server will not be parsed and will be displayed directly on the command line . Example ：

curl http://www.csdn.net

Because you need to jump to HTTPS, So back 301：

<html>

<head><title>301 Moved Permanently</title></head>

<body>

<center><h1>301 Moved Permanently</h1></center>

<hr><center>openresty</center>

</body>

</html>

send out POST request

Use -d When parameters are ,header Of Content-Type Is automatically assigned to application/x-www-form-urlencoded, And send POST request . Example ：

 curl -d 'user= Wanmao society &pwd=onemore' http://csdn.net/login

Because you need to jump to HTTPS, Also return to 301：

<html>

<head><title>301 Moved Permanently</title></head>

<body>

<center><h1>301 Moved Permanently</h1></center>

<hr><center>openresty</center>

</body>

</html>

send out json request

send out json The request also requires two parameters ：-X Parameter assignment HTTP Requested method ,-H Parameter assignment HTTP Requested header. Example ：

curl -X POST -H "Content-Type: application/json; charset=UTF-8" -d '{"user":" Wan Maoxue ","pwd":"onemore"}' http://www.csdn.net/login

among ,-X Parameter assignment HTTP The request method is POST,-H Nibble at specified header Of Content-Type by application/json; charset=UTF-8 ,-d The parameter specifies that the data is {"user":" Wan Maoxue ","pwd":"onemore"} .

Show HTTP Response head

-i The parameter displays the response content of the server at the same time , It also shows HTTP Response head . Example ：

curl -i http://www.csdn.net

The response header of the server will be displayed first , Then leave a blank line , Then display the server response content , as follows ：

HTTP/1.1 301 Moved Permanently

Server: openresty

Date: Thu, 20 Jan 2022 11:59:42 GMT

Content-Type: text/html

Content-Length: 166

Connection: keep-alive

Keep-Alive: timeout=20

Location: https://www.csdn.net/

<html>

<head><title>301 Moved Permanently</title></head>

<body>

<center><h1>301 Moved Permanently</h1></center>

<hr><center>openresty</center>

</body>

</html>

Show the response process

-v The whole response process of parameter display , We can see what happened at the bottom . Example ：

curl -v http://www.csdn.net

It is shown as follows ：

* About to connect() to www.csdn.net port 80 (#0)

*   Trying 39.106.226.142...

* Connected to www.csdn.net (39.106.226.142) port 80 (#0)

> GET / HTTP/1.1

> User-Agent: curl/7.29.0

> Host: www.csdn.net

> Accept: */*

>

< HTTP/1.1 301 Moved Permanently

< Server: openresty

< Date: Thu, 20 Jan 2022 12:07:40 GMT

< Content-Type: text/html

< Content-Length: 166

< Connection: keep-alive

< Keep-Alive: timeout=20

< Location: https://www.csdn.net/

<

<html>

<head><title>301 Moved Permanently</title></head>

<body>

<center><h1>301 Moved Permanently</h1></center>

<hr><center>openresty</center>

</body>

</html>

among , With * The first line indicates curl Additional information provided , With > The first line represents the request header , < The first line represents the response header .

Only response headers are displayed

Sometimes the response content is too long , When you only care about the response header , have access to -I Parameters . Example ：

curl -v http://www.csdn.net

It is shown as follows ：

HTTP/1.1 301 Moved Permanently

Server: openresty

Date: Thu, 20 Jan 2022 12:15:30 GMT

Content-Type: text/html

Content-Length: 166

Connection: keep-alive

Keep-Alive: timeout=20

Location: https://www.csdn.net/

Reference link ：

https://curl.se/docs/manpage.html

https://www.ruanyifeng.com/blog/2019/09/curl-reference.html

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