s3-bucket-list

#!/usr/bin/env python3
import html
import http.client
import os
import shlex
import sys
import urllib.parse


# Arguments
i = 1
withListUrls = False
listUrlsFD = None
startMarker = None
format = '{url}'
args = []
while i < len(sys.argv):
	arg = sys.argv[i]
	if arg == '--help':
		print('s3-bucket-list [options] BUCKETURL', file = sys.stderr)
		print('', file = sys.stderr)
		print('Options:', file = sys.stderr)
		print(f'  --format FORMAT    Modify the output format; FORMAT defaults to {format!r}; available fields: url, key, size, and all fields returned by S3 (e.g. LastModified)', file = sys.stderr)
		print( '  --marker KEY       Start after a particular key instead of from the beginning', file = sys.stderr)
		print( '  --with-list-urls   Enables printing the list URLs retrieved to FD 3', file = sys.stderr)
		sys.exit(1)
	elif arg == '--with-list-urls':
		withListUrls = True
		try:
			listUrlsFD = os.fdopen(3, 'w')
		except OSError:
			print('Error: FD 3 not open', file = sys.stderr)
			sys.exit(1)
	elif arg == '--marker':
		startMarker = sys.argv[i + 1]
		i += 1
	elif arg == '--format':
		format = sys.argv[i + 1]
		i += 1
	else:
		args.append(arg)
	i += 1
assert len(args) == 1, 'Need one argument: bucket URL'
baseUrl = args[0]
assert baseUrl.startswith('http://') or baseUrl.startswith('https://'), 'Argument does not look like an HTTP URL'
if '/' not in baseUrl.split('://', 1)[1] or not baseUrl.endswith('/'):
	baseUrl = f'{baseUrl}/'
hostname = baseUrl.split('://', 1)[1].split('/', 1)[0]


conn = http.client.HTTPSConnection(hostname)
params = {}
if startMarker is not None:
	params['marker'] = startMarker
attempt = 1
while True:
	queryString = urllib.parse.urlencode(params)
	url = f'{baseUrl}{"?" + queryString if queryString else ""}'
	if withListUrls:
		print(f'{url}', file = listUrlsFD)
	conn.request('GET', url[url.index('/', 8):])
	resp = conn.getresponse()
	body = resp.read()
	if b'<Error><Code>InternalError</Code><Message>We encountered an internal error. Please try again.</Message>' in body:
		print(f'Got internal error on {url} on attempt {attempt}; {"retrying" if attempt < 10 else "aborting"}', file = sys.stderr)
		if attempt >= 10:
			if 'marker' in params:
				print(f'To retry, use --marker {shlex.quote(params["marker"])}', file = sys.stderr)
			break
		attempt += 1
		continue
	if not body.startswith(b'<?xml version="1.0" encoding="UTF-8"?>\n<ListBucketResult xmlns="http://s3.amazonaws.com/doc/2006-03-01/">'):
		raise RuntimeError(f'Invalid body: {body[:200]}...')

	if b'<Marker></Marker>' in body[:200] and 'marker' in params:
		raise RuntimeError('Marker loop (empty marker in response despite providing one)')

	# No risk, no fun!
	contents = body.split(b'<Contents>')
	assert all(content.startswith(b'<Key>') for content in contents[1:])
	assert all(content.endswith(b'</Contents>') for content in contents[1:-1])
	assert contents[-1].endswith(b'</Contents></ListBucketResult>')
	contents[-1] = contents[-1][:-len('</ListBucketResult>')]
	for content in contents[1:]:
		key = html.unescape(content[5 : content.index(b'</Key>')].decode('utf-8')) # 5 = len(b'<Key>')
		url = f'{baseUrl}{urllib.parse.quote(key)}'

		tags = content.split(b'>')
		assert len(tags) % 2 == 0
		assert tags[-1] == b''
		assert tags[-2] == b'</Contents'
		openTags = [] # Current open tag hierarchy
		fields = {}
		for tag in tags[:-2]:
			if tag.startswith(b'<'):
				openTags.append(tag[1:])
				continue
			assert openTags
			if tag.endswith(b'</' + openTags[-1]):
				fields[b'>'.join(openTags).decode('utf-8')] = html.unescape(tag[:-(len(openTags[-1]) + 2)].decode('utf-8'))
				openTags.pop()
				continue
			assert False

		size = int(fields['Size']) if 'Size' in fields else None

		try:
			print(format.format(**fields, key = key, url = url, size = size))
		except BrokenPipeError:
			sys.exit(0)
	lastKey = key

	truncated = True if b'<IsTruncated>true</IsTruncated>' in body else (False if b'<IsTruncated>false</IsTruncated>' in body else None)
	assert truncated in (True, False)

	if not truncated:
		break
	if 'marker' in params and params['marker'] == lastKey:
		raise RuntimeError('Marker loop (same last key as previous marker)')
	params['marker'] = lastKey
	attempt = 1