I have several files initialised using paths like this:
String filePath = "/Users/user1/Documents/UWE/Year_3/SDA/GDA GUI Test/Program_Files/modelgraphic1.png";
They display images and when run on another computer the images do not appear. I recall doing something like this in the past:
String filePath = "/.../.../.../.../.../.../GDA GUI Test/Program_Files/modelgraphic1.png";
This isn't working. How can I rectify this? Many thanks.
Boost Filesystem is one of the most reliant libraries, when it comes to paths.
Boost Filesystem Docs => https://www.boost.org/doc/libs/1_66_0/libs/filesystem/doc/index.htm
Reasons for using:
A modern C++ interface, highly compatible with the C++ standard library.
Portability between operating systems.
Error handling and reporting via C++ exceptions (the default) or error codes.
Original answer => https://stackoverflow.com/a/6297807/2303176
Sample Code :
#include <iostream>
#include <boost/filesystem.hpp>
namespace fs = boost::filesystem;
int main ()
{
fs::path dir ("/tmp");
fs::path file ("foo.txt");
fs::path full_path = dir / file;
std::cout << full_path << std::endl;
}
And then running it -
$ g++ ./test.cpp -o test -lboost_filesystem -lboost_system
$ ./test
/tmp/foo.txt
Related
I'm trying to run a helloworld program which uses boost filesystem.
I'm on Windows with MinGW 8.1 and boost 1.70.
The problem is that, although everything compiles, the program doesn't run. I mean, it runs but doesn't print anything, which means the main function is not even executed:
#include <boost/filesystem.hpp>
#include <iostream>
using namespace std;
using namespace std::string_literals;
namespace fs = boost::filesystem;
int main()
{
cout << "Hello Boost!" << endl;
fs::path abHome{"C:/Users/Me"s};
fs::path jsonFile = abHome / "jsonFile.json"s;
if (!fs::exists(jsonFile)) {
cout << "Creating json file from scratch." << endl;
}
}
"Hello Boost" isn't ever printed to the console.
I've compiled with both CMake and g++ from command line to try to better understand what's going on:
g++ main.cpp -o main -L"C:/Code/boost_1_70_0/stage/lib" -lboost_filesystem-mgw81-mt-x64-1_70 -lboost_system-mgw81-mt-x64-1_70 -I"C:/Code/boost_1_70_0"
I've compiled boost for MinGW by following the guide and everything went well, in the output folder I see many different versions of each library based on the default targets (I haven't really picked them, just went with the defaults).
How can I debug the launch of main.exe to see what's causing the crash? It's been many years since I wrote C++ so I need help to get back on track! :)
The problem was, as #kenba pointed out, that the dynamic linking of the boost dlls was failing.
I erroneously thought I had linked the static version of the boost libraries.
To actually achieve that I should have used this command:
g++ main.cpp -o main -L"C:/Code/boost_1_70_0/stage/lib" -l:"libboost_filesystem-mgw81-mt-x64-1_70.a" -l:"libboost_system-mgw81-mt-x64-1_70.a" -I"C:/Code/boost_1_70_0"
instead of the one I posted in the OP.
std::string file = "Cell.txt";
myfile.open (file);
makes a file in current program folder. i dont want the files mixed with the program that is writing them.
std::string file = "Cell\\Cell.txt";
does nothing
std::cout << file << '\n';
prints Cell\Cell.txt
i even tried
std::string file = "\\Cell\\Cell.txt";
did not expect this to work, but tried it anyway
std::string file = "\\\\Cell\\\\Cell.txt";
i have done it before, and can not fine anything on web to help
You say you're not using windows, and yet you create paths like this:
std::string file = "Cell\\Cell.txt";
This isn't a file called Cell.txt in a directory called Cell, but a file called Cell\Cell.txt because backslash path separators are a windows-ism, and under other operating systems they're part of the directory or file name. Use a forward slash instead: Cell/Cell.txt.
Better yet, use the new C++ filesystem libraries to build your paths in a platform-independent sort of manner, and avoid this issue entirely.
#include <experimental/filesystem>
#include <iostream>
namespace fs = std::experimental::filesystem;
int main()
{
auto path = fs::path("Cell") / fs::path("Cell.txt");
std::cout << path.string() << std::endl;
}
This will output
Cell\Cell.txt
under windows and
Cell/Cell.txt
under linux, for example. You can also create directories using create_directory.
(note: this works out of the box on windows under vs2017 and probably 2015, but under g++ you'll need to include an extra library at compile time, like this: g++ -std=c++14 -O2 -Wall -pedantic main.cpp -lstdc++fs)
I am trying to compile a simple program but the MingW C++ compiler cannot find the path. I have two files one is C:\main.cpp the other one is C:\Include\test.h
#include <iostream>
#include "test.h"
using namespace std;
int main()
{
cout << "test" << endl;
getchar();
return 0;
}
I have modified the CPATH, CPLUS_INCLUDE_PATH enviroment vars to include the C:\Include path but it still will not compile with g++ c:\main.cpp -o c:\main.exe
Output from command line.
c:\main.cpp:2:18: fatal error: test.h: No such file or directory
compilation terminated.
Also I used this registry file. Still doesn't work.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\Environment]
"LIBRARY_PATH"="C:\\Include"
"C_INCLUDE_PATH"="C:\\Include"
"CPLUS_INCLUDE_PATH"="C:\\Include"
There's not really enough information here, and storing source files in the root is suspect, but you might try:
g++ -I Include c:\main.cpp -o c:\main.exe
Assuming your cwd is C:\
This plus system restart was needed.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\Environment]
"LIBRARY_PATH"="C:\\Include"
"C_INCLUDE_PATH"="C:\\Include"
"CPLUS_INCLUDE_PATH"="C:\\Include"
I'm trying to link jsoncpp (lib_json) with a c++ project using cmake. It works perfectly fine on one computer, but on another one (with pretty much the same config) i get an error when i execute my app :
dyld: Library not loaded: buildscons/linux-gcc-4.2.1/src/lib_json/libjson_linux-gcc-4.2.1_libmt.dylib
Referenced from: path to executable
Reason: image not found
Any idea what might be causing this ? I don't even understand why it tries to look # buildscons/linux-gcc-4.2.1/src/lib_json/libjson_linux-gcc-4.2.1_libmt.dylib since i put jsoncpp in usr/lib/ and changed the name to libjsoncpp and cmake find the correct path/library.
I also built jsoncpp the exact same way on both computers.
I had the same problem. If you run tool -L libjson_linux-gcc-4.2.1_libmt.dylib you can see some weird relative address to your libjson.... I guess if you replicated this directory structure it would work but that's a bad solution.
What I did instead is that I used .a (libjson_linux-gcc-4.2.1_libmt.a) and linked it staticaly with my binary. In XCode simply under Build Settings -> Linking -> Other Linker Flags I added absolute path to my .a. For me it was /Users/martin/Downloads/jsoncpp-src-0.5.0/libs/linux-gcc-4.2.1/libjson_linux-gcc-4.2.1_libmt.a and that's all.
Of course, I don't know your use case, maybe you really need to link it dynamically.
EDIT: I see now, you mean libjson, and not libjsoncpp (they're different!)
In your titel you talk about jsoncpp, and that's what this answer is for.
But maybe it's useful for people who got confused by the titel too.
You can 'amalgamate' jsoncpp.
From jsoncpp source dir run python amalgamate.py which creates:
dist/jsoncpp.cpp
dist/json/json.h
dist/json/json-forwards.h
Now you have to compile jsoncpp.cpp once and just link against the resulting jsoncpp.o:
g++ -o jsoncpp.o -c jsoncpp.cpp (only once)
g++ -o executable jsoncpp.o main.cpp (every time)
If you get errors, you might have to #define JSON_IS_AMALGAMATION before including json/json.h, but ...
... I tried it and it worked for me. (without #define JSON_IS_AMALGAMATION, that is)
Used code:
#include "json/json.h"
#include "json/json-forwards.h"
int main(int argc, char *argv[])
{
Json::Reader reader;
Json::Value value;
if (!reader.parse("{\"hello\":\"world\"}", value, false))
{
std::cerr << "ERROR: Couldn't parse Json: " << reader.getFormattedErrorMessages() << std::endl;
return -1;
}
std::cout << value.toStyledString() << std::endl;
return 0;
}
I am new to LEDA and I am working on LEDA6.3 Free Edition on OpenSuse 12.1.
As a start I tried to write a simple code "Hello LEDA world" as in the manual http://www.leda-tutorial.org/en/official/ch01s02.html.
#include <LEDA/string.h>
#include <iostream>
using leda::string;
using std::cout;
int main()
{
string msg = "Hello LEDA world!";
cout << msg << "\n";
}
The compilation phase works fine and I generated the .o file.
But they mentioned that this file needs to be linked to the LEDA library and the only library available in the Free edition is the libleda.a and libleda.so
I am trying to link using the following command:
g++ -o welcome welcome.o -L$LEDAROOT -llibleda
What I get is:
/usr/lib64/gcc/x86_64-suse-linux/4.6/../../../../x86_64-suse-linux/bin/ld: cannot find -llibleda
I was wondering if someone could help me with how to link my file with the leda library ? so I can get it to run.
Thanks all.
It is unlikely that the library file is called liblibleda.a or liblibleda.so: when the linker sees a an option of the form -l<name> it will search for a library file named lib<name>.so (for shared libraries) or lib<name>.a (for static libraries). You probably just want to use the option -lleda (unless the LEDA developers did something clever and called the library something like libeda.a so you'd use -leda).
Whether this works will also depend on the compiler options being consistent between the installation and your build.