Function main

example/print_file/print_file_leaf_result.cpp:54–147

The main function, which handles all errors.

// The main function, which handles all errors.
int main( int argc, char const * argv[] )
{
    return leaf::try_handle_all(

        [&]() -> result<int>
        {
            BOOST_LEAF_AUTO(file_name, parse_command_line(argc,argv));

            auto load = leaf::on_error( leaf::e_file_name{file_name} );

            BOOST_LEAF_AUTO(f, file_open(file_name));

            BOOST_LEAF_AUTO(s, file_size(*f));

            std::string buffer(1 + s, '\0');
            BOOST_LEAF_CHECK(file_read(*f, &buffer[0], buffer.size()-1));

            std::cout << buffer;
            std::cout.flush();
            if( std::cout.fail() )
                return leaf::new_error(output_error, leaf::e_errno{errno});

            return 0;
        },

        // Each of the lambdas below is an error handler. LEAF will consider
        // them, in order, and call the first one that matches the available
        // error objects.

        // This handler will be called if the error includes:
        // - an object of type error_code equal to open_error, and
        // - an object of type leaf::e_errno that has .value equal to ENOENT,
        //   and
        // - an object of type leaf::e_file_name.
        []( leaf::match<error_code, open_error>, leaf::match_value<leaf::e_errno, ENOENT>, leaf::e_file_name const & fn )
        {
            std::cerr << "File not found: " << fn.value << std::endl;
            return 1;
        },

        // This handler will be called if the error includes:
        // - an object of type error_code equal to open_error, and
        // - an object of type leaf::e_errno (regardless of its .value), and
        // - an object of type leaf::e_file_name.
        []( leaf::match<error_code, open_error>, leaf::e_errno const & errn, leaf::e_file_name const & fn )
        {
            std::cerr << "Failed to open " << fn.value << ", errno=" << errn << std::endl;
            return 2;
        },

        // This handler will be called if the error includes:
        // - an object of type error_code equal to any of size_error,
        //   read_error, eof_error, and
        // - an optional object of type leaf::e_errno (regardless of its
        //   .value), and
        // - an object of type leaf::e_file_name.
        []( leaf::match<error_code, size_error, read_error, eof_error>, leaf::e_errno const * errn, leaf::e_file_name const & fn )
        {