gistfile1.py

from scrapy.spider import Spider
from scrapy import log

class DummySpider(Spider):
    name = "dummy"
    allowed_domains = ["example.com", "iana.org"]
    start_urls = (
        'http://www.example.com/',
        )

    def __init__(self, *args, **kwargs):
        super(DummySpider, self).__init__(*args, **kwargs)

    def parse(self, response):
        log.msg('DEBUG', level=log.DEBUG)
        log.msg('INFO', level=log.INFO)
        log.msg('WARNING', level=log.WARNING)
        log.msg('ERROR', level=log.ERROR)
        log.msg('CRITICAL', level=log.CRITICAL)

gistfile2.txt

$ scrapy crawl dummy
2014-09-05 16:08:56-0300 [dummy] INFO: Spider opened
2014-09-05 16:08:56-0300 [dummy] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2014-09-05 16:08:56-0300 [scrapy] INFO: Scrapy 0.25.1 started (bot: testspiders)
2014-09-05 16:08:56-0300 [scrapy] INFO: Optional features available: ssl, http11, boto
2014-09-05 16:08:56-0300 [scrapy] INFO: Overridden settings: {'CLOSESPIDER_TIMEOUT': 3600, 'CLOSESPIDER_PAGECOUNT': 1000, 'SPIDER_MODULES': ['testspiders.spiders'], 'NEWSPIDER_MODULE': 'testspiders.spiders', 'BOT_NAME': 'testspiders'}
2014-09-05 16:08:57-0300 [dummy] DEBUG: Crawled (200) <GET http://www.example.com/> (referer: None)
2014-09-05 16:08:57-0300 [scrapy] DEBUG: DEBUG
2014-09-05 16:08:57-0300 [scrapy] INFO: INFO
2014-09-05 16:08:57-0300 [scrapy] WARNING: WARNING
2014-09-05 16:08:57-0300 [scrapy] ERROR: ERROR
2014-09-05 16:08:57-0300 [scrapy] CRITICAL: CRITICAL
2014-09-05 16:08:57-0300 [dummy] INFO: Closing spider (finished)
2014-09-05 16:08:57-0300 [dummy] INFO: Dumping Scrapy stats:
	{'downloader/request_bytes': 214,
	 'downloader/request_count': 1,
	 'downloader/request_method_count/GET': 1,
	 'downloader/response_bytes': 1569,
	 'downloader/response_count': 1,
	 'downloader/response_status_count/200': 1,
	 'finish_reason': 'finished',
	 'finish_time': datetime.datetime(2014, 9, 5, 19, 8, 57, 54845),
	 'log_count/DEBUG': 1,
	 'log_count/INFO': 3,
	 'response_received_count': 1,
	 'scheduler/dequeued': 1,
	 'scheduler/dequeued/memory': 1,
	 'scheduler/enqueued': 1,
	 'scheduler/enqueued/memory': 1,
	 'start_time': datetime.datetime(2014, 9, 5, 19, 8, 56, 576870)}
2014-09-05 16:08:57-0300 [dummy] INFO: Spider closed (finished)

gistfile3.txt

$ scrapy crawl dummy -s LOG_LEVEL=WARNING
2014-09-05 16:09:46-0300 [scrapy] WARNING: WARNING
2014-09-05 16:09:46-0300 [scrapy] ERROR: ERROR
2014-09-05 16:09:46-0300 [scrapy] CRITICAL: CRITICAL

gistfile4.txt

$ scrapy crawl dummy -s LOG_LEVEL=INFO
2014-09-05 16:10:23-0300 [dummy] INFO: Spider opened
2014-09-05 16:10:23-0300 [dummy] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2014-09-05 16:10:23-0300 [scrapy] INFO: Scrapy 0.25.1 started (bot: testspiders)
2014-09-05 16:10:23-0300 [scrapy] INFO: Optional features available: ssl, http11, boto
2014-09-05 16:10:23-0300 [scrapy] INFO: Overridden settings: {'NEWSPIDER_MODULE': 'testspiders.spiders', 'LOG_LEVEL': 'INFO', 'SPIDER_MODULES': ['testspiders.spiders'], 'BOT_NAME': 'testspiders', 'CLOSESPIDER_TIMEOUT': 3600, 'CLOSESPIDER_PAGECOUNT': 1000}
2014-09-05 16:10:23-0300 [scrapy] INFO: INFO
2014-09-05 16:10:23-0300 [scrapy] WARNING: WARNING
2014-09-05 16:10:23-0300 [scrapy] ERROR: ERROR
2014-09-05 16:10:23-0300 [scrapy] CRITICAL: CRITICAL
2014-09-05 16:10:23-0300 [dummy] INFO: Closing spider (finished)
2014-09-05 16:10:23-0300 [dummy] INFO: Dumping Scrapy stats:
	{'downloader/request_bytes': 214,
	 'downloader/request_count': 1,
	 'downloader/request_method_count/GET': 1,
	 'downloader/response_bytes': 1569,
	 'downloader/response_count': 1,
	 'downloader/response_status_count/200': 1,
	 'finish_reason': 'finished',
	 'finish_time': datetime.datetime(2014, 9, 5, 19, 10, 23, 921165),
	 'log_count/INFO': 3,
	 'response_received_count': 1,
	 'scheduler/dequeued': 1,
	 'scheduler/dequeued/memory': 1,
	 'scheduler/enqueued': 1,
	 'scheduler/enqueued/memory': 1,
	 'start_time': datetime.datetime(2014, 9, 5, 19, 10, 23, 166550)}
2014-09-05 16:10:23-0300 [dummy] INFO: Spider closed (finished)