Introduction to curl command

Introduction to curl command

01

Introduction

curl command is a file transfer tool that works from the command line using URL rules.It supports file uploading and downloading, so it is a comprehensive transfer tool, but according to tradition, curl is used to be called a download tool.As a powerful tool, curl supports many protocols including HTTP, HTTPS, ftp, etc. It also supports POST, cookies, authentication, downloading partial files from a specified offset, user agent string, speed limit, file size, progress bar and other features.To automate web page processing and data retrieval, curl can help.The command is briefly described below.

02

Syntax and parameters

Syntax:

curl(options)(parameters)

Common options:

-a/–append

When uploading a file, append to the target file

-A/–user-agent

Set the user agent to send to the server

-b/–cookie

cookie string or file read location

–basic

Use HTTP Basic Authentication

-c/–cookie-jar

Write the cookie to this file after the operation is complete

-C/–continue-at

Continue from breakpoint

-d/–data

HTTP POST method to transmit data

-D/–dump-header

Write header information to this file

-o/–output

Write output to this file

-O/–remote-name

Write output to this file, preserving the filename of the remote file

-R/–remote-time

Preserve remote file time when generating files locally

-u/–user

Set the server user and password

-U/–proxy-user

Set proxy username and password

03

Example

1. File download and upload

curl can download files through different protocols, and by setting specific command parameters, it can flexibly control the download output.Here are a few simple examples:

• Download a single file
  curl http://man.linuxde.net/text.iso
  - download multiple files
  curl –o http://man.linuxde.net/text1.iso –o http://man.linuxde.net/text.iso
  - After downloading the file, output to the specified file,And show progress bar
  curl http://man.linuxde.net/text.iso –o filename.iso –press
  - control download speed
  curl http://man.linuxde.net/text.iso --limit-rate 50k- control download quota
  curl http://man.linuxde.net/text.iso –max-filesize 1000k
  - download from ftp
  curl -u ftpuser:ftppass -O ftp://ftp_server/public_html/xss.php- resume the upload
  curl http://man.linuxde.net/text.iso -C offset
  #Offset is an integer in bytes. If you let curl automatically infer the correct resume position, use -C -: curl -C -http://man.linuxde.net/text.iso- File Upload
  curl --form “[email protected]” http://hostname/resource
  

2. Web page process processing

Curl can transmit data to the server and supports common protocols such as http, https, ftp, etc., so it can also be used to verify the correctness of different requests and the format of the returned data.Here are some common examples:

• View page code
  curl www.so.com
  - GETRequest
  curl 123-_360search POST request
  curl -d "userId=28090443&premium=100" "http://www.so.com//addStrategyKeyword
  - show headers
  curl –i http://www.so.com
  - show the communication process
  curl –v www.so.com
  - Cookie usage
  curl –cookie “type=xxx” www.so.com
  - add header information
  curl --header “xxx:xxx” http://www.so.com
  - http authentication curl –user name:password www.so.com
  

04

Summary

The above are just the common methods of curl command. If there are any deficiencies, you are welcome to correct them. For more detailed usage, you can check this link: http://man.linuxde.net/curl