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guivi

About the blog

In this blog I will keep track of projects I develop though out this year and may be in the future. For now it is juts a testing ground for developing the blog itself but I hope as I put more material it will become a good place for me to hold information.

Simple NMEA Parsing

C/C++ Programming Posted by guiviPosted on 05 Apr, 2023 13:39:58 
#include <iostream>
#include <map>
#include <sstream>
#include <string>
#include <vector>

std::string GetFieldId(std::string sentenceId, int fieldIndex)
{
    // Combine the sentence ID and field index to create the field ID
    std::ostringstream oss;
    oss << sentenceId << "-" << fieldIndex;
    return oss.str();
}

std::vector<std::string> SplitString(std::string str, char delimiter)
{
    std::vector<std::string> parts;
    std::stringstream ss(str);
    std::string part;
    
    while (std::getline(ss, part, delimiter)) {
        parts.push_back(part);
    }
    
    return parts;
}

std::map<std::string, std::string> ParseNmeaString(std::string nmeaString)
{
    std::map<std::string, std::string> components;
    if (nmeaString.length() < 7 || nmeaString[0] != '$' || nmeaString[nmeaString.length()-3] != '*') {
        return components;
    }
    
    std::string sentence = nmeaString.substr(1, nmeaString.length()-4);
    std::string checksum = nmeaString.substr(nmeaString.length()-2, 2);
    
    std::vector<std::string> parts = SplitString(sentence, ',');
    std::string sentenceId = parts[0];
    
    for (int i = 1; i < parts.size(); i++) {
        components[GetFieldId(sentenceId, i)] = parts[i];
    }
    
    return components;
}

int main()
{
    std::string sentence = "$GPGGA,092750.000,5321.6802,N,00630.3372,W,1,8,1.03,61.7,M,55.2,M,,*76";
    std::map<std::string, std::string> components = ParseNmeaString(sentence);

    // Print the components to the console
    for (auto const& component : components) {
        std::cout << component.first << ": " << component.second << std::endl;
    }
    
    return 0;
}


How do I give www-data user to a folder in my home folder?

Web Development Posted by guiviPosted on 05 Apr, 2023 13:37:23

First, add yourself into the group www-data

usermod -a -G www-data (your username)

Then:

chgrp www-data /home/myuser/folderA
chmod g+rwxs /home/myuser/folderA

Should do the trick unless the permissions on your /home/myuser do not permit other users access.

The first command changes the group ownership of the folder to that of the webserver. The second command gives members of the www-data group read, write, enter-directory rights, and the group s flag will ensure that any files that get created inside that directory take www-data as the group – so if you create a file as myuser the www-data user will have access.

Nb. this also depends on the umask settings of both your user account and the webserver: you need to make sure that files created in folderA have group rw access (and directories created within need group rwx)

If your webserver does not have enter rights into your /home/myuser dir (quite sensible) then it’s not going to get in there unless you do something else. Two solns:

  1. sudo mount --bind /home/myuser/folderA /var/www/mysite/folderA (this is an ugly hack and would have to be repeated after reboot. But a powerful trick, also can be used to make folders accessible inside SSH jails.)
  2. Simply move the shared folder somewhere else, e.g. /home/shared-stuff/folderA.

The 2nd option is nicest. Let’s say the stuff in folderA is really public and you don’t care who sees it, you can set it up like

sudo mkdir -m777 /home/shared-stuff

Then you can put inside that, say, folderA with permissions as above, and folderB that www-data should not have access to with different permissions, e.g.

$ cd /home/shared-stuff ; ls -l
drwxrwsr-x 2 myuser www-data   4096 Jan 17 21:46 folderA
drwxrwx--- 2 myuser myuser     4096 Jan 17 21:46 folderB

Source: https://askubuntu.com/a/244410/957246