I need to be able to modify a complex config file from within my C/C++ program (whichever is going to be easier and more convenient to use in this case, probably C++). The idea is that the program computes the values that it needs to insert into the file, then writes them.
The config file itself looks like this:
^looots of stuff I won't be using^
option blah.blah.something "value"
option blah.blah.someotherthing "value"
Now, many of the options are logically connected, for instance:
option blah.blah.car.engine "value"
option blah.blah.car.color "value"
I don't really have an idea how to reach those lines that I'm interested in. Should I skip to a specific line and then search for a quotation mark and modify what's after it? That doesn't seems like a reliable and flexible solution, does it?
Related
I want to modify value corresponding to a key in configuration file using cpp.
Eg:
key=value
has to be changed to
key=new_value
I works with 'sed' command, but is there some possible way to do it using cpp way.
Implementation fails when the string to be changed is less than the existing one. Is that not really possible using cpp?
You basically only have one option: Rewrite the configuration file, write out all configuration options from the start.
Trying to move around contents of a text file if one line changes length (bigger or smaller) is possible, but it's much more work than just rewriting it.
It's either that or the working solution using sed, which can be called from inside the program using the system function.
I have some documentation strings embedded within the source code (C/C++ files) as XML tags and I'd like to know what's the most minimal solution to make vim autoclose the tags (closest matching tag).
I've found closetag.vim but is there away to do this neatly without modifying anything but the .vimrc file?
Vim has no built-in support for that, so the closetag.vim plugin is the proper and easiest solution. (I use it myself, too!) Of course, you can develop your own simple mappings (that search backwards for an open tag, get that, drop the attributes, add the slash, and insert that), but:
that will either be very simplistic and therefore often wrong
or ends up with as much complexity as closetag, becoming a reimplementation of that plugin
If some rather strange restrictions (e.g. a custom primitive sync across systems) only allow you to manipulate the ~/.vimrc itself, you could just append the entire plugin's code to it (though I'd recommend against such an ugly hack).
Apparently this supposed to be possible. For example opening and operating on a file with NOTEPAD, or HxD. But aren't they all text files...how would one specify which text editor to open the file and operate on the file with using the WINDOWS API. It is certainly not in "CreateFile".
Hopefully I'm understanding your question... The easiest way to do this is to launch the desired editor and pass the filename as an argument, rather than "invoking" the file (which will launch the default program associated with the file type).
For example, notepad.exe mytextfile.txt or gvim.exe mytextfile.txt.
If the editor is not on your %PATH%, you'll need to use a full path file name.
What are you trying to do, exactly? You could:
Maintain a list of editors that you expect to be installed and have entries for in the system's PATH (bad idea)
Have an editor/editors that you want to use, query the Windows registry to find the installation path of the editors (using RegGetValue), and launch the editor with CreateProcess) (a little better idea)
Query the registry to get the default editor for a given file type and then launch that editor using CreateProcess. (best idea)
But it all depends on what your goal is really.
Edit based on requirements
So, just so we're on the same page, from C++, you want to:
Take a command line parameter to your C++ application (filename)
Open that file in an arbitrary editor
Detect when the user has made changes to that file
Operate on the file contents
Is that correct?
If so, you could:
Use Boost libs to compute a CRC for the current data in the file
Launch an editor using one of the methods I initially described
Stick in a tight loop and sleep so you don't chew up resources while the initially computed CRC matches one calculated every iteration of the loop
Of course, there are all kinds of issues that you'd have to deal with (that's just a super simple way of describing the algorithm I might use), such as:
What happens if the user doesn't change the file?
What happens if the file isn't found?
I'm sure that there are a number of different methods of doing this, but this is the easiest method that I can think of at the moment (while still being able to be fairly certain of the changes).
Disclaimer: I haven't implemented something like this, so I might be completely off base ;)
Are you looking for the ShellExecute() or ShellExecuteEx() APIs on Windows? They'll launch whatever program is registered for a file (generally based on the filename extention).
I'm just starting to dig into boost::program_options for the first time. I like it quite a bit. However, what I'm trying to accomplish with it doesn't seem to be something its designers have accounted for.
I want to use boost::program_options to parse both command line options as well as config files. So far so good. Additionally, though, I would like to be able to check for updated settings (say from a new config file) that could override the previously parsed settings in my variables_map.
Granted, I could do a separate parse and try to merge the two maps. Perhaps that's what I'll end up doing. I'm just wondering, though, if anyone has done anything like this before and has come up with a slick solution.
My Qt application should be able to create/open/save a single "Project" at once. What is the painless way to store project's settings in a file? Should it be XML or something less horrible?
Of course data to be stored in a file is a subject to change over time.
What I need is something like QSettings but bounded to a project in my application rather than to the whole application.
You can use QSettings to store data in a specific .ini file.
From the docs:
Sometimes you do want to access settings stored in a specific file or registry path. On all platforms, if you want to read an INI file directly, you can use the QSettings constructor that takes a file name as first argument and pass QSettings::IniFormat as second argument. For example:
QSettings settings("/home/petra/misc/myapp.ini",
QSettings::IniFormat);
I order to make it user editable, I would stick to plain text with one key = values by line, like in most of the Linux apps.
However this is only for the settings, not for the complete project's data which I suppose requires more complex structures.
So maybe JSON ?
Pro XML:
You can have a look at it in an editor
You can store any kind of string in any language in it (unicode support)
It's simple to learn
More than one program can read the same XML
It's easy to structure your data with XML. When you use key/value lists, for example, you'll run into problems when you need to save tree-like structures.
Contra XML
The result is somewhat bloated
Most programming languages (especially old ones like C++) have no good support for XML. The old XML APIs were designed in such a way that they could be implemented in any language (smallest common denominator). 'nuff said.
You need to understand the concept of "encoding" (or "charset"). While this may look trivial at first glance, there are some hidden issues which can bite you. So always test your code with some umlauts and even kanji (Japanese characters) to make sure you got it right.