# curl 快速参考

*HTTP 请求、头部、认证、表单、调试*

> Source: curl Documentation (curl.se/docs) · MIT

## 基本用法

### 简单请求

```
curl https://example.com          # GET request
curl -o file.html https://url     # save to file
curl -O https://url/file.tar.gz   # save with remote name
curl -L https://url               # follow redirects
```

### 常用参数

| Command | Description |
|---------|-------------|
| `-s` | 静默模式（不显示进度） |
| `-S` | 静默模式下显示错误 |
| `-f` | HTTP 错误时静默失败 |
| `-L` | 跟随重定向 |
| `-o file` | 输出写入文件 |
| `-O` | 使用远端文件名保存 |
| `-C -` | 续传中断的下载 |
| `--max-time 30` | 30 秒后超时 |

## HTTP 方法

### GET 与 HEAD

```
curl https://api.example.com/users
curl -I https://example.com       # HEAD (headers only)
curl -i https://example.com       # include response headers
```

### POST

```
curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d '{"name":"Jo","email":"jo@ex.com"}'
```

### PUT、PATCH 与 DELETE

```
curl -X PUT https://api.example.com/users/1 \
  -d '{"name":"Updated"}'
curl -X PATCH https://api.example.com/users/1 \
  -d '{"email":"new@ex.com"}'
curl -X DELETE https://api.example.com/users/1
```

## 请求头

### 设置请求头

```
curl -H "Content-Type: application/json" URL
curl -H "Accept: text/html" URL
curl -H "X-Custom: value" URL
curl -H "Header1: v1" -H "Header2: v2" URL
```

### 响应头

| Command | Description |
|---------|-------------|
| `-i` | 在输出中包含响应头 |
| `-I` | 仅获取响应头（HEAD） |
| `-D file` | 将响应头写入文件 |
| `-w '%{http_code}'` | 打印 HTTP 状态码 |

## 认证

### Basic 认证与 Token 认证

```
curl -u user:pass https://api.example.com
curl -H "Authorization: Bearer TOKEN" URL
curl -u user:pass --digest URL
curl --negotiate -u : URL   # Kerberos/SPNEGO
```

### 认证方式

| Command | Description |
|---------|-------------|
| `-u user:pass` | Basic 认证 |
| `--digest` | HTTP Digest 认证 |
| `--negotiate` | Kerberos/SPNEGO 认证 |
| `--ntlm` | NTLM 认证 |
| `-n` | 使用 ~/.netrc 凭证 |

## 数据与表单

### 发送数据

```
curl -d "key=val&key2=val2" URL   # form urlencoded
curl -d @data.json URL            # data from file
curl --data-raw '{"raw":"json"}' URL
curl --data-urlencode "q=hello world" URL
```

### 文件上传

```
curl -F "file=@photo.jpg" URL
curl -F "file=@doc.pdf;type=application/pdf" URL
curl -F "field=value" -F "file=@img.png" URL
```

### Multipart 与 URL 编码对比

| Command | Description |
|---------|-------------|
| `-d` | application/x-www-form-urlencoded |
| `-F` | multipart/form-data |
| `--json` | 简写：设置 Content-Type + Accept 为 JSON |
| `-T file` | 通过 PUT 上传文件 |

## SSL/TLS

### 证书选项

```
curl --cacert ca.pem URL          # custom CA bundle
curl --cert client.pem URL        # client certificate
curl --cert client.pem --key key.pem URL
curl -k URL                       # skip TLS verify (dev only)
```

### TLS 参数

| Command | Description |
|---------|-------------|
| `-k / --insecure` | 跳过 TLS 证书验证 |
| `--cacert file` | 使用自定义 CA 证书 |
| `--cert file` | 客户端证书 |
| `--key file` | 客户端私钥 |
| `--tlsv1.2` | 强制最低 TLS 1.2 |
| `--tlsv1.3` | 强制最低 TLS 1.3 |

## 输出与调试

### 详细输出与追踪

```
curl -v URL                       # verbose output
curl --trace dump.txt URL         # full trace to file
curl --trace-ascii - URL          # trace to stdout
curl -w "\n%{http_code}\n" URL    # custom output format
```

### Write-Out 变量

| Command | Description |
|---------|-------------|
| `%{http_code}` | HTTP 响应状态码 |
| `%{time_total}` | 总耗时（秒） |
| `%{time_connect}` | 建立连接耗时 |
| `%{size_download}` | 下载字节数 |
| `%{speed_download}` | 平均下载速度 |
| `%{redirect_url}` | 重定向 URL（如有） |
| `%{ssl_verify_result}` | SSL 验证结果（0 = 正常） |

### Write-Out 示例

```
curl -s -o /dev/null -w \
  "code: %{http_code}\ntime: %{time_total}s\n" \
  https://example.com
```

## 常用模式

### API 工作流

```
# GET JSON and pipe to jq
curl -s https://api.example.com/data | jq '.items[]'
# POST JSON with auth
curl -s -H "Authorization: Bearer $TOKEN" \
  --json '{"key":"val"}' https://api.example.com
```

### 下载模式

```
# Download with progress bar
curl -# -O https://releases.example.com/v2.tar.gz
# Resume interrupted download
curl -C - -O https://releases.example.com/v2.tar.gz
# Download multiple files
curl -O https://url/file1 -O https://url/file2
```

### 脚本辅助

```
# Check if URL is reachable
curl -sf -o /dev/null https://example.com && echo OK
# Save cookies and reuse
curl -c cookies.txt -b cookies.txt URL
# Rate-limit request
curl --limit-rate 100k URL
```

## 代理与网络

### 代理设置

```
curl -x http://proxy:8080 URL
curl -x socks5://proxy:1080 URL
curl --proxy-user user:pass -x http://proxy:8080 URL
curl --noproxy "*.local,localhost" URL
```

### DNS 与解析

| Command | Description |
|---------|-------------|
| `--resolve host:port:addr` | 强制 DNS 解析到指定地址 |
| `--dns-servers 8.8.8.8` | 使用自定义 DNS 服务器 |
| `--interface eth0` | 使用指定网络接口 |
| `-4 / -6` | 强制 IPv4 / IPv6 |

## 配置与进阶

### 配置文件

```
# ~/.curlrc — default options
--silent
--location
--max-time 30

# Use config file explicitly
curl -K myconfig.txt URL
```

### 实用参数

| Command | Description |
|---------|-------------|
| `--retry 3` | 遇到临时错误时重试 |
| `--retry-delay 2` | 重试间隔（秒） |
| `--compressed` | 请求并解压 gzip/br |
| `--limit-rate 100k` | 限制传输速度 |
| `-Z` | 并行传输（curl 7.66+） |
| `--create-dirs` | 为 -o 创建路径目录 |