curl - HTTP客户端

用于发起HTTP请求和传输数据的命令行工具。

基础请求

GET请求

# Simple GET request
curl https://api.example.com

# Save output to file
curl https://example.com -o output.html
curl https://example.com/file.zip -O  # Use remote filename

# Follow redirects
curl -L https://example.com

# Show response headers
curl -i https://example.com

# Show only headers
curl -I https://example.com

# Verbose output (debugging)
curl -v https://example.com

POST请求

# POST with data
curl -X POST https://api.example.com/users \
  -d "name=John&email=john@example.com"

# POST JSON data
curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d '{"name":"John","email":"john@example.com"}'

# POST from file
curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d @data.json

# Form upload
curl -X POST https://api.example.com/upload \
  -F "file=@document.pdf" \
  -F "description=My document"

其他HTTP方法

# PUT request
curl -X PUT https://api.example.com/users/1 \
  -H "Content-Type: application/json" \
  -d '{"name":"Jane"}'

# DELETE request
curl -X DELETE https://api.example.com/users/1

# PATCH request
curl -X PATCH https://api.example.com/users/1 \
  -H "Content-Type: application/json" \
  -d '{"email":"newemail@example.com"}'

请求头与身份验证

自定义请求头

# Add custom header
curl -H "User-Agent: MyApp/1.0" https://example.com

# Multiple headers
curl -H "Accept: application/json" \
     -H "Authorization: Bearer token123" \
     https://api.example.com

身份验证

# Basic auth
curl -u username:password https://api.example.com

# Bearer token
curl -H "Authorization: Bearer YOUR_TOKEN" \
  https://api.example.com

# API key in header
curl -H "X-API-Key: your_api_key" \
  https://api.example.com

# API key in URL
curl "https://api.example.com?api_key=your_key"

高级功能

超时与重试

# Connection timeout (seconds)
curl --connect-timeout 10 https://example.com

# Max time for entire operation
curl --max-time 30 https://example.com

# Retry on failure
curl --retry 3 https://example.com

# Retry delay
curl --retry 3 --retry-delay 5 https://example.com

Cookie处理

# Send cookies
curl -b "session=abc123" https://example.com

# Save cookies to file
curl -c cookies.txt https://example.com

# Load cookies from file
curl -b cookies.txt https://example.com

# Both save and load
curl -b cookies.txt -c cookies.txt https://example.com

代理设置

# Use HTTP proxy
curl -x http://proxy.example.com:8080 https://api.example.com

# With proxy authentication
curl -x http://proxy:8080 -U user:pass https://api.example.com

# SOCKS proxy
curl --socks5 127.0.0.1:1080 https://api.example.com

SSL/TLS配置

# Ignore SSL certificate errors (not recommended for production)
curl -k https://self-signed.example.com

# Use specific SSL version
curl --tlsv1.2 https://example.com

# Use client certificate
curl --cert client.crt --key client.key https://example.com

# Show SSL handshake details
curl -v https://example.com 2>&1 | grep -i ssl

响应处理

输出格式化

# Silent mode (no progress bar)
curl -s https://api.example.com

# Show only HTTP status code
curl -s -o /dev/null -w "%{http_code}" https://example.com

# Custom output format
curl -w "\nTime: %{time_total}s\nStatus: %{http_code}\n" \
  https://example.com

# Pretty print JSON (with jq)
curl -s https://api.example.com | jq '.'

范围请求

# Download specific byte range
curl -r 0-1000 https://example.com/large-file.zip

# Resume download
curl -C - -O https://example.com/large-file.zip

文件操作

文件下载

# Download file
curl -O https://example.com/file.zip

# Download with custom name
curl -o myfile.zip https://example.com/file.zip

# Download multiple files
curl -O https://example.com/file1.zip \
     -O https://example.com/file2.zip

# Resume interrupted download
curl -C - -O https://example.com/large-file.zip

文件上传

# FTP upload
curl -T file.txt ftp://ftp.example.com/upload/

# HTTP PUT upload
curl -T file.txt https://example.com/upload

# Form file upload
curl -F "file=@document.pdf" https://example.com/upload

测试与调试

API测试

# Test REST API
curl -X GET https://api.example.com/users
curl -X GET https://api.example.com/users/1
curl -X POST https://api.example.com/users -d @user.json
curl -X PUT https://api.example.com/users/1 -d @updated.json
curl -X DELETE https://api.example.com/users/1

# Test with verbose output
curl -v -X POST https://api.example.com/login \
  -H "Content-Type: application/json" \
  -d '{"username":"test","password":"pass"}'

性能测试

# Measure request time
curl -w "Total time: %{time_total}s\n" https://example.com

# Detailed timing
curl -w "\nDNS: %{time_namelookup}s\nConnect: %{time_connect}s\nTLS: %{time_appconnect}s\nTransfer: %{time_starttransfer}s\nTotal: %{time_total}s\n" \
  -o /dev/null -s https://example.com

常见调试方法

# Show request and response headers
curl -v https://api.example.com

# Trace request
curl --trace-ascii trace.txt https://api.example.com

# Include response headers in output
curl -i https://api.example.com

常见模式

快速JSON API测试：

curl -s https://api.github.com/users/octocat | jq '{name, bio, followers}'

带进度条下载：

curl -# -O https://example.com/large-file.zip

POST JSON并提取字段：

curl -s -X POST https://api.example.com/login \
  -H "Content-Type: application/json" \
  -d '{"user":"test","pass":"secret"}' | jq -r '.token'

检查URL是否可访问：

if curl -s --head --fail https://example.com > /dev/null; then
  echo "Site is up"
else
  echo "Site is down"
fi

并行下载：

for i in {1..10}; do
  curl -O https://example.com/file$i.jpg &
done
wait

实用标志

• -X：HTTP方法（GET、POST、PUT、DELETE等）
• -d：发送的数据（POST/PUT）
• -H：自定义头部
• -o：输出文件
• -O：使用远程文件名保存
• -L：跟随重定向
• -i：在输出中包含头部
• -I：仅头部
• -v：详细输出
• -s: 静默模式
• -S: 即使在静默模式下也显示错误
• -f: 在HTTP错误时静默失败
• -k: 不安全（忽略SSL）
• -u: 基本身份验证
• -F: 多部分表单数据
• -b: 发送Cookie
• -c: 保存Cookie
• -w: 自定义输出格式

提示

• 在脚本中使用-s以抑制进度条
• 组合使用-sS实现静默但显示错误
• 使用-L用于处理重定向（例如，短网址）
• 添加-v用于调试
• 使用jq处理JSON响应
• 将常用请求保存为shell别名或脚本
• 使用--config处理复杂的可复用请求

文档

官方文档：https://curl.se/docs/手册：man curlHTTP方法：https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods