external print function how compile - c++

Question

I created two Files where the second File should print a std::vector.
That's my main.cpp:
#include <vector>
int main() {
std::vector<int> vec;
vec.push_back(1);
vec.push_back(2);
vec.push_back(3);
vec.push_back(4);
vec.push_back(5);
return 0;
}
That's the print.cpp
#include <iostream>
#include <iterator>
#include <algorithm>
#include <vector>
template <typename T> void printVec(T vec) {
std::copy(vec.begin(), vec.end(), std::ostream_iterator<int>(std::cout, " "));
std::cout << std::endl;
}
template void printVec< std::vector<int> >(std::vector<int> t);
I compiled those files with:
g++ -g main.cpp -o main.o
g++ -g -c print.cpp -o print.o
g++ -o main main.o print.o
and get following error
main.o: In function `_start':
(.text+0x0): multiple definition of `_start'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.text+0x0): first defined here
main.o: In function `_fini':
(.fini+0x0): multiple definition of `_fini'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o:(.fini+0x0): first defined here
main.o:(.rodata+0x0): multiple definition of `_IO_stdin_used'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.rodata.cst4+0x0): first defined here
main.o: In function `__data_start':
(.data+0x0): multiple definition of `__data_start'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.data+0x0): first defined here
main.o: In function `__data_start':
(.data+0x8): multiple definition of `__dso_handle'
/usr/lib/gcc/x86_64-linux-gnu/4.6/crtbegin.o:(.data+0x0): first defined here
main.o: In function `_init':
(.init+0x0): multiple definition of `_init'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o:(.init+0x0): first defined here
/usr/lib/gcc/x86_64-linux-gnu/4.6/crtend.o:(.dtors+0x0): multiple definition of `__DTOR_END__'
main.o:(.dtors+0x8): first defined here
/usr/bin/ld: error in main.o(.eh_frame); no .eh_frame_hdr table will be created.
collect2: ld returned 1 exit status
How am I supposed to get it to run?

Answer 1

Change:
g++ -g main.cpp -o main.o
g++ -g -c print.cpp -o print.o
g++ -o main main.o print.o
to:
g++ -g -c main.cpp -o main.o
g++ -g -c print.cpp -o print.o
g++ -o main main.o print.o
Or alternatively you can just combine all 3 operations into one (and enable warnings while you're at it):
g++ -g -Wall -o main main.cpp print.cpp