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Linux does not install curl by default. Curl is a file transfer tool that uses URL to work on the command line. Not all linux systems come with curl commands. For example, a concise version of the Linux system may not exist, just install it by executing the "yum install curl" command.

The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

Curl command

Curl command in Linux system is a file transfer tool that uses URL to work on the command line, which is usually used to access services and download files in Linux system.

The curl command supports HTTP, HTTPS, FTP and other protocols, and can be used to simulate service requests and upload and download files.

Does linux install curl by default?

Linux does not install curl by default.

Not all systems come with the curl command, and a concise version of the Linux system may not exist, so you can use the yum command to install curl,yum install curl.

After the installation is complete, you can use the curl-- version command to view the curl version information on the system.

Syntax format of the curl command

The standard syntax for the curl command is: curl [options] [url], where options is used to specify the parameter item and url is the requested service address.

Execute the request without a parameter entry: curl http://www.baidu.com, in which case the command execution directly requests the specified service address and outputs the source code of the request result to the Linux command line.

Related parameters:

The curl command implements rich functions through different parameter items. Common parameter items are:

-I, that is,-- head, indicates that the request result displays the response header information.

-o, that is,-- output, followed by the file path, indicates that the request result is written to the specified file

-s, namely-- silent, silent mode, indicates that no additional information will appear in the request result at this time

-w, that is,-- write-out [format]. The parameter is followed by a format string, indicating that the output is specified after the command is executed.

You can usually use commands when testing whether the interface is working:

Curl-o / dev/null-s-w% {http_code} http://www.baidu.com

At this time, the return source code of the service is written to the empty address null, and the silent mode is enabled, and the http status code is output after the request. If the request is successful, 200 is returned.

For more available parameter items for curl, you can use the curl-h/--help query.

Upload and download files using curl

1. File upload

Command parameters for uploading files are provided in curl. You can initiate a request with-F followed by file information.

Curl-F 'file=@test.png;type=image/png' http://www.baidu.com/upload

Among them, it is important to pay attention to:

When using the-F parameter, curl considers the file to be uploaded, and specifies-H Content-Type: multipart/form-datas by default, indicating the format of file upload.

When the-F parameter specifies file information, you can specify multiple files and file types, which are separated by multiple parameters.

2. File download

There are many ways to download files in the curl command, which are:

For the requested result data, you can use the redirect function of Linux to save to a file. > > index.html

Request the file and save it with the-Ogamot Muro parameter, curl-o a.jpg http://www.baidu.com/b.jpg

If you request to download a file, you can also specify the-# parameter, which will show the progress of the file download and close it with-s.

If the file download process stops, you can add the-C parameter to execute the breakpoint continuation of the file.

Use curl to simulate GET/POST requests

Curl command supports POST request, Cookies, authentication and other operations, so it can also be well applied to the simulation of service interface requests in the development process.

1. Simulate GET request

A GET request is actually the simplest service request, which carries parameter information through url stitching, so you can directly use the simplest request method of curl.

Simulate the GET request to obtain data during development:

Curl http://localhost:8080/getUserInfo?id=1 .

2. Simulate POST request

POST request is a way of data submission, which is submitted with parameter information when requesting the service address. The method of carrying parameter information is also provided in the curl command.

-X, the parameter is followed by the request method, and the POST request can be executed

-H, the parameter is followed by a string. You can specify the request header information, such as "Content-Type:application/json" to indicate that the data is transmitted in json format.

-d. The parameter is followed by a string. You can specify the content of the request parameter in the form of a string. You should pay attention to the use of the-d parameter.

This command can be used multiple times to specify multiple parameter information respectively.

You can also use-d 'key1=val1&key2=val2' to specify more than one parameter at a time

If you specify a parameter of type json, you can pass a json object using-d'{"id": 1, "name": "shone"}'

After using the-d parameter, the request type defaults to POST, and the-X parameter can be omitted.

The-d parameter can also specify a file as a parameter, using @ followed by the file name,-d "@ test.txt"

For a complete POST request, it can be:

Curl-H "Content-Type:application/json"-d'{"id": 1, "name": "shone"} 'http://localhost:8080/queryInfo

3. Use Cookies

When making a service request, the browser usually saves the request information to Cookies. You can use the-D parameter to specify the Cookies to save the request.

Curl-o page1.html-D cookie.txt http://www.baidu.com

The curl command can also simulate the browser's request, using-A to specify browser information to imitate the browser to initiate the request and save the Cookies

Curl-A "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)"-o page.html-D cookie.txt http://mydomain.net

For the saved Cookie information, you can use the-b parameter to specify the Cookie when you request.

This is the end of curl-b cookie.txt http://www.baidu.com 's article on "whether linux installs curl by default". Thank you for reading! I believe you all have a certain understanding of "whether linux installs curl by default". If you want to learn more, you are welcome to follow the industry information channel.

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