mailinabox/management/editconf.py

#!/usr/bin/python3
#
# This is a helper tool for editing configuration files during the setup
# process. The tool is given new values for settings as command-line
# arguments. It comments-out existing setting values in the configuration
# file and adds new values either after their former location or at the
# end.
#
# The configuration file has settings that look like:
#
# NAME=VALUE
#
# If the -s option is given, then space becomes the delimiter, i.e.:
#
# NAME VALUE
#
# If the -c option is given, then the supplied character becomes the comment character
#
# If the -w option is given, then setting lines continue onto following
# lines while the lines start with whitespace, e.g.:
#
# NAME VAL
#   UE

# create the new config file in memory

def edit_conf(filename, settings, folded_lines, testing):
	found = set()
	buf = ""
	input_lines = list(open(filename, "r+"))

	while len(input_lines) > 0:
		line = input_lines.pop(0)

		# If this configuration file uses folded lines, append any folded lines
		# into our input buffer.
		if folded_lines and line[0] not in (comment_char, " ", ""):
			while len(input_lines) > 0 and input_lines[0][0] in " \t":
				line += input_lines.pop(0)

		# See if this line is for any settings passed on the command line.
		for i in range(len(settings)):
			# Check that this line contain this setting from the command-line arguments.
			name, val = settings[i].split("=", 1)
			m = re.match(
				"(\s*)"
				+ "(" + re.escape(comment_char) + "\s*)?"
				+ re.escape(name) + delimiter_re + "(.*?)\s*$",
				line, re.S)
			if not m: continue
			indent, is_comment, existing_val = m.groups()

			# If this is already the setting, do nothing.
			if is_comment is None and existing_val == val:
				# It may be that we've already inserted this setting higher
				# in the file so check for that first.
				if i in found: break
				buf += line
				found.add(i)
				break

			# comment-out the existing line (also comment any folded lines)
			if is_comment is None:
				buf += comment_char + line.rstrip().replace("\n", "\n" + comment_char) + "\n"
			else:
				# the line is already commented, pass it through
				buf += line

			# if this option oddly appears more than once, don't add the setting again
			if i in found:
				break

			# add the new setting
			buf += indent + name + delimiter + val + "\n"

			# note that we've applied this option
			found.add(i)

			break
		else:
			# If did not match any setting names, pass this line through.
			buf += line

	# Put any settings we didn't see at the end of the file.
	for i in range(len(settings)):
		if i not in found:
			name, val = settings[i].split("=", 1)
			buf += name + delimiter + val + "\n"

	if not testing:
		# Write out the new file.
		with open(filename, "w") as f:
			f.write(buf)
	else:
		# Just print the new file to stdout.
		print(buf)

# Run standalone
if __name__ == "__main__":
	import sys, re

	# sanity check
	if len(sys.argv) < 3:
		print("usage: python3 editconf.py /etc/file.conf [-s] [-w] [-c <CHARACTER>] [-t] NAME=VAL [NAME=VAL ...]")
		sys.exit(1)

	# parse command line arguments
	filename = sys.argv[1]
	settings = sys.argv[2:]

	delimiter = "="
	delimiter_re = r"\s*=\s*"
	comment_char = "#"
	folded_lines = False
	testing = False
	while settings[0][0] == "-" and settings[0] != "--":
		opt = settings.pop(0)
		if opt == "-s":
			# Space is the delimiter
			delimiter = " "
			delimiter_re = r"\s+"
		elif opt == "-w":
			# Line folding is possible in this file.
			folded_lines = True
		elif opt == "-c":
			# Specifies a different comment character.
			comment_char = settings.pop(0)
		elif opt == "-t":
			testing = True
		else:
			print("Invalid option.")
			sys.exit(1)

	# sanity check command line
	for setting in settings:
		try:
			name, value = setting.split("=", 1)
		except:
			import subprocess
			print("Invalid command line: ", subprocess.list2cmdline(sys.argv))
			sys.exit(1)

	edit_conf(filename, settings, folded_lines, testing)