title: C++ on mac : linker command failed with exit code 1 (use -v to see invocation)
body: <pre><code>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)
  </code></pre>
  
  <p><br/></p>
  
  <pre><code>#include &lt;iostream&gt;
  using namespace std;
  
  int main() {
      double radius, circumference, area; // Declare 3 floating-point variables
      const double PI = 3.14159265;       // Declare and define PI
  
  cout &lt;&lt; "Enter the radius: ";  // Prompting message
  cin &gt;&gt; radius;                 // Read input into variable radius
  
  // Compute area and circumference
  area = radius * radius * PI;
  circumference = 2.0 * radius * PI;
  
  // Print the results
  cout &lt;&lt; "The radius is: " &lt;&lt; radius &lt;&lt; endl;
  cout &lt;&lt; "The area is: " &lt;&lt; area &lt;&lt; endl;
  cout &lt;&lt; "The circumference is: " &lt;&lt; circumference &lt;&lt; endl;
  
  return 0;
  }
  </code></pre>