Unable to read INI file Parsing using boost::program_options - c++

I am a newbie in c++ and boost. I am attempting to read (later write) to INI file using boost::program_options. I even tried using boost::property_tree.
Both(program_options & property_tree) work perfectly when std::stringstream s("[test]\n""a=2\n""b=3\n") is used, BUT NOT when std::ifstream s("dimension.ini"). I have put files: dimension.ini, Rcasdim.hpp/cpp in the same folder, and also have relevant boost lib files in search directory.
INI File
[Section]
a=2
b=3
Purpose:
I need to dynamically set the "Value" (at the start ONLY) for a Particular "Key" in INI file & Later USE that Previously set "Value" for that "Key" by other project files (more, as a toggle)
#include boost/program_options/detail/config_file.hpp
#include boost/program_options/parsers.hpp
namespace pod = boost::program_options::detail;
class CRcasdim
{
public:
CRcasdim(){};
~CRcasdim(){};
std::string getrcasdim(float);
private:
std::string sd;
};
std::string CRcasdim::getrcasdim(float d)
{
//std::stringstream s("[Section]\n""a=2\n""b=3\n"); WORKS
std::ifstream s("dimension.ini"); DOESNT WORK
if(!s)
{
std::cerr<<"error"<<std::endl;
}
std::set<std::string> options;
std::map<std::string, std::string> parameters;
options.insert("Section.a");
options.insert("Section.b");
try
{
for (pod::config_file_iterator i(s, options), e ; i != e; ++i)
parameters[i->string_key] = i->value[0];
}
catch(std::exception& e)
{
std::cerr<<"Exception: ";
}
if (d==2)
sd = parameters["Section.a"];
else if (d==3)
sd = parameters["Section.b"];
return sd;
}

You don't need to put the ini file and the hpp/cpp files in the same folder.
The dimension.ini file has be in the same folder like your binary(executable on linux .exe on windows).
The location depends on your build system and your platform and most probably some things I forgot.

Related

How to have a config file outside a CPP dll file

I have a config.txt file which is in my source folder. I use it to store my baseURL. When i build the dll the config file gets capsulated into one dll.
I am trying to add a config file which will reside outside the dll, so that i can change the base url when needed.
using namespace std;
struct Config {
string baseurl;
};
void loadConfig(Config& config) {
ifstream fin("config.txt");
string line;
while (getline(fin, line)) {
istringstream sin(line.substr(line.find("=") + 1));
if (line.find("baseurl") != -1)
sin >> config.baseurl;
}
}
#and to access the values
Config config;
loadConfig(config);
Also can the dll file access an external config file when placed in the same folder.?
any solutions for this?

Get all file recursively from C:/

I'm trying to retrieve all files from the C:/ directory using Boost library.
I can retrieve all files when the input is a file path with a directory (e.g : C:\Windows), but I get an error when the specified path is only C:\. I also tried with C: but Boost search file from my project directory and not from the root.
I have also added an exclusion to C:\Windows and this part works great.
So how to launch recursive_directory_iterator from C:\ ?
Here is my code :
//string rootPath = boost::filesystem::current_path().root_directory().string();
string rootPath = "C:";
string exclusionPath = rootPath+"\\"+"Windows";
void myClass::getFile()
{
for (boost::filesystem::recursive_directory_iterator end, dir(rootPath); dir != end; ++dir)
{
string filePath = dir->path().string();
if (boost::filesystem::is_regular_file(*dir) && filePath.find(exclusionPath) == string::npos)
{
cout << filePath << endl;
}
}
}
If you are using the c++17 standard library, you can take advantage of the standard filesystem library. It works just like the boost filesystem and the two libraries have a very similar API.
You have to include the filesystem header via
#include <filesystem>
You can recursively iterate through each file in a directory by calling:
for (std::filesystem::directory_entry entry : std::filesystem::recursive_directory_iterator(rootPath))
That will give you a directory entry, which, just like the boost directory entry, contains a path. I was able to replicate your example code with the standard library and got a working example like so:
#include <filesystem>
#include <string>
#include <iostream>
std::filesystem::path rootPath = "C:";
std::filesystem::path exclusionPath = rootPath / "Windows";
int main()
{
for (std::filesystem::directory_entry entry : std::filesystem::recursive_directory_iterator(rootPath))
{
std::string filePath = entry.path().string();
if (std::filesystem::is_regular_file(entry.path()) && filePath.find(exclusionPath.string()) == std::string::npos)
{
std::cout << filePath << std::endl;
}
}
}
As you can see, I converted the strings you use for paths above to paths. This is not necessary but it is better to construct a path up-front, because else every function you call will construct a new path with the string you put into it. Paths weirdly use the / operator to append two paths together, so on Windows
std::filesystem::path exclusionPath = rootPath / "Windows";
will give you C:\Windows.

opening a file in random named folder using c/c++

I'm trying to code a program where it opens and reads a file automatically. But the problem is the file is stored in a folder which name is unknown. I only know where the folder is located and the file's name. How to get to that file's path in char* ?
Edit: example: d:\files\<random folder>\data.txt
I don't know the name of random folder but I know that it exists in d:\files
Since this is tagged windows, you might as well use the Windows API functions:
FindFirstFile()
FindNextFile()
to enumerate and loop through all the files in a given directory.
To check for a directory, look at dwFileAttributes contained in the WIN32_FIND_DATA structure (filled by the calls to Find...File()). But make sure to skip . and .. directories. If needed, this can be done recursively.
You can check the links for some examples, or see Listing the Files in a Directory.
In case you are using MFC, you can use CFileFind (which is a wrapper around the API functions):
CFileFind finder;
BOOL bWorking = finder.FindFile(_T("*.*"));
while (bWorking)
{
bWorking = finder.FindNextFile();
TRACE(_T("%s\n"), (LPCTSTR)finder.GetFileName());
}
Just for fun, I implemented this using the new, experimental <filesystem> FS Technical Specification supported by GCC 5.
#include <iostream>
#include <experimental/filesystem>
// for readability
namespace fs = std::experimental::filesystem;
int main(int, char* argv[])
{
if(!argv[1])
{
std::cerr << "require 2 parameters, search directory and filename\n";
return EXIT_FAILURE;
}
fs::path search_dir = argv[1];
if(!fs::is_directory(search_dir))
{
std::cerr << "First parameter must be a directory: " << search_dir << '\n';
return EXIT_FAILURE;
}
if(!argv[2])
{
std::cerr << "Expected filename to search for\n";
return EXIT_FAILURE;
}
// file to search for
fs::path file_name = argv[2];
const fs::directory_iterator dir_end; // directory end sentinel
// used to iterate through each subdirectory of search_dir
fs::directory_iterator dir_iter(search_dir);
for(; dir_iter != dir_end; ++dir_iter)
{
// skip non directories
if(!fs::is_directory(dir_iter->path()))
continue;
// check directory for file
// iterate through files in this subdirectory dir_iter->path()
auto file_iter = fs::directory_iterator(dir_iter->path());
for(; file_iter != dir_end; ++file_iter)
{
// ignore directories and wrong filenames
if(fs::is_directory(file_iter->path())
|| file_iter->path().filename() != file_name)
continue;
// Ok we found it (the first one)
std::cout << "path: " << file_iter->path().string() << '\n';
return EXIT_SUCCESS;
}
}
// Not found
std::cout << file_name << " was not found in " << search_dir.string() << '\n';
return EXIT_FAILURE;
}
The idea is: list the directories under d:\files and try to open
the file in each directory.
There isn't (yet) a standard C++ way of getting all the existing files/directories. A crude but easy way of doing this would be
system("dir d:\\files /b /ad > tmpfile");
This lists all directories (/ad), redirected to a temporary file. Then open the file:
std::ifstream list("tmpfile");
And read it:
std::string dirname;
std::string filename;
while (std::getline(list, dirname))
{
filename = "d:\\files\\" + dirname + "\\data.txt";
if ( ... file exists ... )
break;
}
I call this method crude because it has problems that are hard/impossible to fix:
It overwrites a potentially useful file
It doesn't work if current directory is read-only
It will only work in Windows
It might be possible to use _popen and fgets instead of redirecting to file.

Use shell symbols in directory path

I want to open a file with my program, and I want to use shell symbols to make it easier for me to locate the file. Is there an easy way to have the shell expand out my file path before I use it on runtime. I'm looking for a function that does this.
~/.foo.bar -> /home/someuser/.foo.bar
Is there some easy way to have the shell preprocess the paths to files before opening the file?
You can use wordexp:
#include <wordexp.h>
std::string wordexp(std::string var, int flags = 0)
{
wordexp_t p;
if(!wordexp(var.c_str(), &p, flags))
{
if(p.we_wordc && p.we_wordv[0])
var = p.we_wordv[0];
wordfree(&p);
}
return var;
}
int main()
{
std::cout << wordexp("~/test") << '\n';
}

how to search the computer for files and folders

i need a way to search the computer for files like Windows Explorer. i want my program to search lets say hard drive c:. i need it to search C:\ for folders and files (just the ones you could see in c:\ then if the user clicks on a file on the list like the folder test (C:\test) it would search test and let the user see what files/folders are in it.
Since you mentioned windows, the most straight forward winapi way to do it is with FindFirstFile and FindNextFile functions.
edit: Here's an example that shows you how to enumerate all files/folders in a directory.
#include <Windows.h>
#include <iostream>
int main()
{
WIN32_FIND_DATA file;
HANDLE search_handle=FindFirstFile(L"C:\\*",&file);
if (search_handle)
{
do
{
std::wcout << file.cFileName << std::endl;
}while(FindNextFile(search_handle,&file));
FindClose(search_handle);
}
}
This will be OS dependent. The SO question
How can I get a list of files in a directory using C or C++?
handles this problem well. You can download DIRENT here.
Now that you have this, I'd recommend recursively searching for a file with a DFS/BFS algorithm. You can assume the whole directory structure is a tree where each file is a leaf node and each subdirectory is an internal node.
So all you have to do is,
Get the list of files/folders in a directory with a function such as:
void getFilesFolders(vector<string> & dir_list, const string & folder_name)
If it's a directory, go to 1 with the directory name
If it's a file, terminate if it's the file you're looking for, else move on to the next file.
boost::filesystem can be a cross-platform solution for that (check out for such functions in it).
You can use Directory class members to do this with C# or managed C++. See the following MSDN article:
http://support.microsoft.com/kb/307009
If you wish to use C++ with MFC you can use CFileFind
http://msdn.microsoft.com/en-us/library/f33e1618%28v=VS.80%29.aspx
You'll have to supply your own browse window to present the file system tree.
Or you can use one of the directory/file controls to do both for you.
#include <Windows.h>
#include <iostream>
int FindF(char* pDirectory)
{
char szFindPath[MAX_PATH] = {0};
strcpy(szFindPath, pDirectory);
strcat(szFindPath, "\\*");
WIN32_FIND_DATA file;
HANDLE search_handle=FindFirstFile(szFindPath,&file);
if (search_handle)
{
do
{
if(file.dwFileAttributes == FILE_ATTRIBUTE_DIRECTORY)
{
strcpy(szFindPath, pDirectory);
strcat(szFindPath, "\\");
strcat(szFindPath, file.cFileName);
FindF(szFindPath);
}
std::wcout << file.cFileName << std::endl;
}while(FindNextFile(search_handle,&file));
CloseHandle(search_handle);
}
}
There really is no need to use 3rd party library to accomplish this. This is a short, independent function which lists all files (with their paths) in a directory, including subdiretories' files. std::string folderName has to finish with \, and if you want to list all files on computer, just create a loop in calling function along with GetLogicalDriveStrings (It returns strings with \, so it couldn't be more convenient in this case).
void FindAllFiles(std::string folderName)
{
WIN32_FIND_DATA FileData;
std::string folderNameWithSt = folderName + "*";
HANDLE FirstFile = FindFirstFile(folderNameWithSt.c_str(), &FileData);
if (FirstFile != INVALID_HANDLE_VALUE) {
do {
if (strcmp(FileData.cFileName, ".") != 0 && strcmp(FileData.cFileName, "..") != 0)
{
if(FileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
{
std::string NewPath = folderName + FileData.cFileName;
NewPath = NewPath + "\\";
FindAllFiles(NewPath);
}
else
{
std::cout /*<< folderName*/ << FileData.cFileName << std::endl;
}
}
} while(FindNextFile(FirstFile, &FileData));
}
}
This is ASCII version, remember that files and folders can be named in Unicode