C++ on mac : linker command failed with exit code 1 (use -v to see invocation)

Question

Ld /Users/rahulshrestha/Library/Developer/Xcode/DerivedData/101-bdjjlwlibkuaakgjcxqoslsirofh/Build/Products/Debug/101 normal x86_64
    cd /Users/rahulshrestha/Dropbox/C++/101
    export MACOSX_DEPLOYMENT_TARGET=10.9
    /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk -L/Users/rahulshrestha/Library/Developer/Xcode/DerivedData/101-bdjjlwlibkuaakgjcxqoslsirofh/Build/Products/Debug -F/Users/rahulshrestha/Library/Developer/Xcode/DerivedData/101-bdjjlwlibkuaakgjcxqoslsirofh/Build/Products/Debug -filelist /Users/rahulshrestha/Library/Developer/Xcode/DerivedData/101-bdjjlwlibkuaakgjcxqoslsirofh/Build/Intermediates/101.build/Debug/101.build/Objects-normal/x86_64/101.LinkFileList -mmacosx-version-min=10.9 -stdlib=libc++ -Xlinker -dependency_info -Xlinker /Users/rahulshrestha/Library/Developer/Xcode/DerivedData/101-bdjjlwlibkuaakgjcxqoslsirofh/Build/Intermediates/101.build/Debug/101.build/Objects-normal/x86_64/101_dependency_info.dat -o /Users/rahulshrestha/Library/Developer/Xcode/DerivedData/101-bdjjlwlibkuaakgjcxqoslsirofh/Build/Products/Debug/101

duplicate symbol _main in:
    /Users/rahulshrestha/Library/Developer/Xcode/DerivedData/101-bdjjlwlibkuaakgjcxqoslsirofh/Build/Intermediates/101.build/Debug/101.build/Objects-normal/x86_64/main.o
    /Users/rahulshrestha/Library/Developer/Xcode/DerivedData/101-bdjjlwlibkuaakgjcxqoslsirofh/Build/Intermediates/101.build/Debug/101.build/Objects-normal/x86_64/praca.o
ld: 1 duplicate symbol for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

#include <iostream>
using namespace std;

int main() {
    double radius, circumference, area; // Declare 3 floating-point variables
    const double PI = 3.14159265;       // Declare and define PI

cout << "Enter the radius: ";  // Prompting message
cin >> radius;                 // Read input into variable radius

// Compute area and circumference
area = radius * radius * PI;
circumference = 2.0 * radius * PI;

// Print the results
cout << "The radius is: " << radius << endl;
cout << "The area is: " << area << endl;
cout << "The circumference is: " << circumference << endl;

return 0;
}

Answer 1

You can only have one main() - you decide which one you need to keep and which one needs to be deleted. Keep only one page, with the main() method.

Answer 2

该错误消息告诉您您需要了解的所有内容-您有两个主电源-一个在main.cpp中，一个在praca.cpp中。只能有1个主方法。

Answer 3

Others on the thread have already indicated the issue here. I will try give the context.

When you compile your program the c++ compiler looks for main function definition amongst the object files it has compiled as an entry-point to invoke your program.

As your error indicates the compiler finds 2 main function definition one in praca.o(praca.cpp ?) and the other in main.o(main.cpp ?)

So you have to choose either the main in main.cpp or praca.cpp and remove the other.