How are arguments in a configuration file parsed regardless of position?

e.g. A configuration file can have

CFLAGS = "xyz"
CXXFLAGS = "xyz"

OR

CXXFLAGS = "xyz"
CFLAGS = "xyz"

Best implementation I could think of would be to just split the argument and feed the left side into a switch

for line in file
    x = line.split("=")
    switch(x[0])
        case CFLAGS
             do cflags
        case CXXFLAGS
             do cxxflags

But how do people who have way more experience than me do it? I know theres probably some open source programs who do this but I wouldn't even know where t开发者_如何学编程o look in their source for this. I program mainly in python and C so implementations/pseudocode/whattolookup in both would be preferred although other languages are fine also.

Thanks in advance.

P.S. try to avoid saying any form of re, regex, regexp, regular expressions, or any derivative thereof in your answers unless its unavoidable :P.

In Python just use the ConfigParser module which will parse .ini-like configuration files for you.

Re implementing this yourself, I find it convenient to view configuration data as a kind of dictionary. This naturally translates to Python's dicts, so if I split the line to <key> = <value> I just go on and update:

confdict[key] = value

With this scheme, the order of the keys in the configuration file doesn't matter, just like it doesn't matter in the dictionary itself - as long as you can lookup values for keys, you're happy.

If you look under the hood of ConfigParser, for example (the relevant method is _read), you will find this is exactly what it does. The options are kept in a dictionary (one per section, because .ini configuration files have one level of hierarchy). Lines are parsed from the file using regular expressions and key, value pairs are added to the dictionary as I described above.

This is Python. In C, I imagine there are quite a few libraries for doing this, but implementing your own would follow exactly the same algorithm. You'd use some kind of associative array data structure for the dictionary (hash table, tree, or whatever, doesn't really matter) and do the same parsing & assigning.

As Eli Bendersky says, in Python you should just use the provided ConfigParser.

If you insist on doing it yourself, his method of storing the configuration as a dictionary is one I recommend. Another way is to map the options to functions which process the values and do something with them:

# Map the options to functions to handle them.
handlers = {
    'CFLAGS': some_function,
    'CXXFLAGS': other_function,
}

# Loop through each option.
for line in configuration:
    # Get the option and value.
    option, value = line.split('=')
    option = option.strip().upper()
    value = value.strip()

    # Try to find a handler and process the option.
    handler = handlers.get(option)
    if handler:
        handler(option, value)
    else:
        raise Exception('Unknown option.')

Obviously, the handler functions must be able to accept the option and value parameters you're passing it.