链接：https://www.cnblogs.com/huangSir-devops/p/18875948

Detailed Usage of the curl Command in Linux Systems

The table of contents is here, please message me for any modifications

• • Overview of curl
• • Application Scenarios of curl
• • Basic Usage of curl
• • Installation
• • Syntax of curl
• • Common Options and Parameters
• • Common Use Cases

Overview of curl

Official Documentation: https://curl.se/docs/GitHub Repository: https://github.com/curl/curl

curl, short for Client URL, is a command-line tool and library for transferring data via URLs, supporting over 100 protocols (HTTP/HTTPS, FTP, SMTP, POP3, RTSP, DICT, etc.).

Its main functions include sending network requests, receiving responses, supporting file uploads/downloads, handling authentication, proxies, cookies, redirection, and other complex network operations.

Its lightweight, simplicity, cross-platform compatibility (Linux, Windows, Mac), and script-friendly nature (suitable for automation and API testing) make it popular among programmers.

Application Scenarios of curl

• • API Debugging: Testing RESTful interfaces (GET/POST/PUT/DELETE, etc.).
• • File Transfer: Downloading remote files, uploading files to servers (e.g., FTP/SCP).
• • Network Diagnostics: Checking server response status, analyzing request/response headers.
• • Data Collection: Scraping web content (be mindful of the website’s robots.txt protocol).
• • Script Automation: Integrating network requests in Shell/Python scripts.

Basic Usage of curl

Installation

|     |     |
| --- | --- |
|     | # For Debian-based Linux |
|     | apt install -y curl |
|     |     |
|     | # For CentOS-based Linux |
|     | yum install -y curl |

Syntax of curl

|     |     |
| --- | --- |
|     | # where options are the option parameters, and url is the request path |
|     | curl [options] [url] |

Common Options and Parameters

Request Control Options

• • -X, –request: Specify the request method (GET, POST, PUT, DELETE…)

|     |     |
| --- | --- |
|     | curl -X GET https://www.baidu.com |

• • -H, –header: Add request headers, can be specified multiple times

|     |     |
| --- | --- |
|     | curl -H "content-type: application/json; charset=utf-8" \ 
|     | -H "Authorization: Bearer TOKEN" \ 
|     | https://api.example.com |

• • -d: Send POST data (form data, automatically sets Content-Type: application/x-www-form-urlencoded)

|     |     |
| --- | --- |
|     | curl -d "name=John&age=30" https://api.example.com/submit |

• • -D, –dump-header: Save response headers to a file

|     |     |
| --- | --- |
|     | curl -D headers.txt https://www.baidu.com |

• • -L, –location: Automatically follow redirects (301/302 status codes)

|     |     |
| --- | --- |
|     | curl -L http://www.baidu.com |

• • -b, –cookie: Send cookies (format: name=value or file path)

|     |     |
| --- | --- |
|     | curl -b "sessionid=12345" https://example.com |

• • -c, –cookie-jar: Save cookies returned by the server to a local file for later access

|     |     |
| --- | --- |
|     | curl -c cookies.txt https://example.com/login |

Data Transfer Options

• • -o: Save downloaded content to a file

|     |     |
| --- | --- |
|     | curl -o download.zip https://example.com/file.zip |

• • -O: Download content, file name follows the remote file

|     |     |
| --- | --- |
|     | curl -O https://example.com/file.zip |

• • -d: Send POST data (form data, automatically sets Content-Type: application/x-www-form-urlencoded)

|     |     |
| --- | --- |
|     | curl -d "name=John&age=30" https://api.example.com/submit |

• • -F, –form: Send form files/data (simulating browser upload, automatically sets multipart/form-data)

|     |     |
| --- | --- |
|     | curl -F "[email protected]" https://api.example.com/upload |

• • -T, –upload-file: Upload a file (PUT or POST request)

|     |     |
| --- | --- |
|     | curl -T report.pdf ftp://ftp.example.com/upload/ |

Output and Debugging Options

• • -v, –verbose: Show detailed debugging information (request headers, response headers, connection process, etc.)

|     |     |
| --- | --- |
|     | curl -v https://www.baidu.com |

• • -s, –silent: Silent mode (does not show progress bar), but error messages will still be displayed.

|     |     |
| --- | --- |
|     | curl -s https://example.com > content.txt |

• • -S, –show-error: Show error messages in silent mode (must be used with -s)

|     |     |
| --- | --- |
|     | curl -sS https://invalid-url.com |

• • –trace: Trace the request process (more detailed debugging logs)

|     |     |
| --- | --- |
|     | curl --trace trace.log https://example.com |

Other Advanced Options

• • –proxy: Use a proxy server (format: host:port, supports HTTP/SOCKS5)

|     |     |
| --- | --- |
|     | curl --proxy 127.0.0.1:8080 https://example.com |

• • –insecure, -k: Ignore HTTPS certificate verification (unsafe, for testing only)

|     |     |
| --- | --- |
|     | curl -k https://self-signed.example.com |

• • –user, -u: Basic authentication (username:password)

|     |     |
| --- | --- |
|     | curl -u admin:password123 https://auth.example.com |

• • –ntlm: Use NTLM authentication (Windows domain environment)

|     |     |
| --- | --- |
|     | curl --ntlm -u domain\user:password https://intranet.example.com |

• • –limit-rate: Limit transfer speed (e.g., 100k means 100KB/s)

|     |     |
| --- | --- |
|     | curl --limit-rate 100k https://example.com/big-file.zip |

• • –retry: Number of retries after failure (useful during network fluctuations)

|     |     |
| --- | --- |
|     | curl --retry 5 https://flaky-api.example.com |

• • –range: Resume downloads (request partial content, useful for downloading large files)

|     |     |
| --- | --- |
|     | curl --range 0-1024 https://example.com/large-file.zip |

• • -x, –compressed: Enable compression (automatically handles gzip/bzip2 encoding)

|     |     |
| --- | --- |
|     | curl -x https://example.com |

Common Use Cases

• • Simulating Domain Access

|     |     |
| --- | --- |
|     | # Purpose: Request 192.0.2.1, but tell the server "I am fake.example.com" |
|     | curl -H "Host: fake.example.com" http://192.0.2.1 |

• • Downloading Files

|     |     |
| --- | --- |
|     | # Short option -o, specify output file name |
|     | curl -o filename.html https://example.com/page.html |
|     |     |
|     | # Uppercase -O, use the file name from the URL |
|     | curl -O https://example.com/filename.zip |

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