from IPython.core.magic import register_cell_magic

@register_cell_magic
def cpp(line, cell):
    """Compile, execute C++ code, and return the standard output."""

    # We first retrieve the current IPython interpreter instance.
    ip = get_ipython()

    # We define the source and executable filenames.
    source_filename = '_temp.cpp'
    program_filename = '_temp'

    # We write the code to the C++ file.
    with open(source_filename, 'w') as f:
        f.write(cell)

    # We compile the C++ code into an executable.
    compile = ip.getoutput("g++ {0:s} -o {1:s}".format(
        source_filename, program_filename))

    # We execute the executable and return the output.
    output = ip.getoutput('./{0:s}'.format(program_filename))

    print('\n'.join(output))

%%cpp
#include<iostream>
int main()
{
    std::cout << "Hello world!";
}