curl - Cliente HTTP y Transferencia de Datos¶

Comandos curl completos para solicitudes HTTP, pruebas de API y transferencia de datos en todas las plataformas.

Solicitudes HTTP Básicas¶

Solicitudes GET¶

Comando	Descripción
`curl https://api.example.com`	Solicitud GET básica
`curl -v https://api.example.com`	Salida detallada con encabezados
`curl -i https://api.example.com`	Incluir encabezados de respuesta
`curl -I https://api.example.com`	Solicitud HEAD únicamente
`curl -L https://example.com`	Seguir redirects
### Solicitudes POST
Comando	Descripción
---------	-------------
`curl -X POST https://api.example.com`	Solicitud POST básica
`curl -d "data" https://api.example.com`	POST con datos
`curl -d @file.json https://api.example.com`	Datos POST desde archivo
`curl -F "file=@upload.txt" https://api.example.com`	Carga de archivo
### Otros Métodos HTTP
Comando	Descripción
---------	-------------
`curl -X PUT -d "data" https://api.example.com`	Solicitud PUT
`curl -X DELETE https://api.example.com/item/1`	Solicitud DELETE
`curl -X PATCH -d "data" https://api.example.com`	Solicitud PATCH
## Encabezados y Autenticación

Encabezados Personalizados¶

Comando	Descripción
`curl -H "Content-Type: application/json" url`	Establecer tipo de contenido
`curl -H "Authorization: Bearer token" url`	Autenticación de token Bearer
`curl -H "User-Agent: MyApp/1.0" url`	Agente de usuario personalizado
`curl -H "Accept: application/xml" url`	Encabezado Accept
### Métodos de Autenticación
Comando	Descripción
---------	-------------
`curl -u username:password url`	Autenticación básica
`curl -u username url`	Solicitar contraseña
`curl --oauth2-bearer token url`	Token de portador OAuth2
`curl --digest -u user:pass url`	Autenticación Digest
### Autenticación con Clave API
`# API key in header curl -H "X-API-Key: your-api-key" https://api.example.com # API key in query parameter curl "https://api.example.com?api_key=your-api-key" # Multiple headers curl -H "Authorization: Bearer token" \ -H "Content-Type: application/json" \ https://api.example.com`

Formatos de Datos¶

Datos JSON¶

# POST JSON data
curl -X POST \
     -H "Content-Type: application/json" \
     -d '\\\\{"name":"John","age":30\\\\}' \
     https://api.example.com/users

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

Datos de Formulario¶

# URL-encoded form data
curl -d "name=John&age=30" https://api.example.com/users

# Multipart form data
curl -F "name=John" -F "age=30" https://api.example.com/users

# File upload with form data
curl -F "file=@document.pdf" \
     -F "description=Important document" \
     https://api.example.com/upload

Datos XML¶

# POST XML data
curl -X POST \
     -H "Content-Type: application/xml" \
     -d '<user><name>John</name><age>30</age></user>' \
     https://api.example.com/users

Operaciones con Archivos¶

Descargar Archivos¶

Comando	Descripción
`curl -O https://example.com/file.zip`	Descargar con nombre original
`curl -o myfile.zip https://example.com/file.zip`	Descargar con nombre personalizado
`curl -C - -O https://example.com/file.zip`	Reanudar descarga interrumpida
`curl --limit-rate 100k -O url`	Limitar velocidad de descarga
### Subir Archivos
Comando	Descripción
---------	-------------
`curl -T file.txt ftp://server/path/`	Cargar mediante FTP
`curl -F "file=@upload.txt" url`	Carga de archivos HTTP
`curl --upload-file file.txt url`	Subir archivo PUT
### Múltiples Archivos
`# Download multiple files curl -O https://example.com/file1.zip -O https://example.com/file2.zip # Upload multiple files curl -F "file1=@doc1.pdf" -F "file2=@doc2.pdf" https://api.example.com/upload`

Opciones Avanzadas¶

Timeouts y Reintentos¶

Comando	Descripción
`curl --connect-timeout 10 url`	Tiempo de espera de conexión (segundos)
`curl --max-time 30 url`	Tiempo total máximo
`curl --retry 3 url`	Reintentar en caso de fallo
`curl --retry-delay 5 url`	Intervalo entre reintentos
### Opciones SSL/TLS
Comando	Descripción
---------	-------------
`curl -k url`	Ignorar errores de certificado SSL
`curl --cacert ca.pem url`	Usar certificado de CA personalizado
`curl --cert client.pem url`	Usar certificado de cliente
`curl --tlsv1.2 url`	Forzar versión TLS
### Proxy y Red
Comando	Descripción
---------	-------------
`curl --proxy proxy.example.com:8080 url`	Usar proxy HTTP
`curl --socks5 proxy.example.com:1080 url`	Usar proxy SOCKS5
`curl --interface eth0 url`	Utilizar interfaz de red específica
`curl --dns-servers 8.8.8.8 url`	Usar servidores DNS personalizados
## Salida y Formato

Control de Salida¶

Comando	Descripción
`curl -s url`	Modo silencioso (sin progreso)
`curl -S url`	Mostrar errores incluso en modo silencioso
`curl -o /dev/null url`	Descartar salida
`curl -w "%\\{http_code\\}" url`	Mostrar solo código de estado HTTP
### Información de Respuesta
`# Get detailed timing information curl -w "@curl-format.txt" https://example.com # curl-format.txt content: # time_namelookup: %\\\\{time_namelookup\\\\}\n # time_connect: %\\\\{time_connect\\\\}\n # time_appconnect: %\\\\{time_appconnect\\\\}\n # time_pretransfer: %\\\\{time_pretransfer\\\\}\n # time_redirect: %\\\\{time_redirect\\\\}\n # time_starttransfer: %\\\\{time_starttransfer\\\\}\n # ----------\n # time_total: %\\\\{time_total\\\\}\n`

Procesamiento JSON¶

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

# Extract specific fields
curl -s https://api.example.com/users|jq '.[]|.name'

# Filter results
curl -s https://api.example.com/users|jq '.[]|select(.age > 25)'

Pruebas y Depuración¶

Pruebas de API¶

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Test REST API endpoints¶

curl -X GET https://api.example.com/users curl -X POST -d '\\{"name":"John"\\}' https://api.example.com/users curl -X PUT -d '\\{"name":"Jane"\\}' https://api.example.com/users/1 curl -X DELETE https://api.example.com/users/1

Test with different content types¶

curl -H "Accept: application/json" https://api.example.com/users curl -H "Accept: application/xml" https://api.example.com/users ```### Pruebas de Rendimiento

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

# Test multiple requests
for i in \\\\{1..10\\\\}; do
  curl -w "%\\\\{time_total\\\\}\n" -o /dev/null -s https://example.com
done
```### Manejo de Errores
```bash
# Check HTTP status codes
http_code=$(curl -s -o /dev/null -w "%\\\\{http_code\\\\}" https://example.com)
if [ $http_code -eq 200 ]; then
    echo "Success"
else
    echo "Error: HTTP $http_code"
fi
```## Configuración y Scripts
```bash
# ~/.curlrc configuration file
user-agent = "MyApp/1.0"
connect-timeout = 10
max-time = 30
show-error
silent
```### Archivo de Configuración
```bash
#!/bin/bash
# API testing script

BASE_URL="https://api.example.com"
API_KEY="your-api-key"

# Function to make authenticated requests
api_request() \\\\{
    local method=$1
    local endpoint=$2
    local data=$3

    curl -X "$method" \
         -H "Authorization: Bearer $API_KEY" \
         -H "Content-Type: application/json" \
         $\\\\{data:+-d "$data"\\\\} \
         "$BASE_URL$endpoint"
\\\\}

# Usage examples
api_request GET "/users"
api_request POST "/users" '\\\\{"name":"John","email":"john@example.com"\\\\}'
```### Scripting en Bash
```bash
# Use environment variables for sensitive data
export API_TOKEN="your-secret-token"
curl -H "Authorization: Bearer $API_TOKEN" https://api.example.com

# Read credentials from file
curl -K credentials.txt https://api.example.com

# credentials.txt:
# header = "Authorization: Bearer your-token"
```## Mejores Prácticas de Seguridad
```bash
# Always verify SSL certificates in production
curl --cacert /path/to/ca-bundle.crt https://api.example.com

# For development only (not recommended for production)
curl -k https://self-signed.example.com
```### Autenticación Segura
```bash
# Download webpage
curl -L https://example.com > page.html

# Follow redirects and save cookies
curl -L -c cookies.txt -b cookies.txt https://example.com

# Set user agent to avoid blocking
curl -H "User-Agent: Mozilla/5.0 (compatible; bot)" https://example.com
```### Verificación de Certificados
```bash
# GitHub API example
curl -H "Authorization: token your-github-token" \
     https://api.github.com/user/repos

# Weather API example
curl "https://api.openweathermap.org/data/2.5/weather?q=London&appid=your-api-key"

# Slack webhook example
curl -X POST \
     -H "Content-Type: application/json" \
     -d '\\\\{"text":"Hello from curl!"\\\\}' \
     https://hooks.slack.com/services/YOUR/SLACK/WEBHOOK
```## Casos de Uso Comunes
```bash
# Upload to cloud storage
curl -X PUT \
     -H "Authorization: Bearer token" \
     --upload-file document.pdf \
     https://api.storage.com/files/document.pdf

# Download with progress bar
curl --progress-bar -O https://example.com/largefile.zip
```### Web Scraping

| Problema | Solución |
|---------|----------|
| SSL certificate errors | Use `-k` for testing, fix certificates for production |
| Connection timeout | Increase `--connect-timeout` value |
| Slow downloads | Use `--limit-rate` to control bandwidth |
| Authentication failures | Verificar credenciales y método de autenticación |### Integración de API
```bash
# Verbose output for debugging
curl -v https://example.com

# Trace all network activity
curl --trace trace.txt https://example.com

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

# Test connectivity
curl -I --connect-timeout 5 https://example.com