Насчёт С не знаю, но на С++ (а значит, наверное, и на С) так:
#include
#include
using std::cout;
using std::endl;
typedef enum { enSuccess, enWrongCmdLine, enFileOpenError } __ExitCodes;
int main(int argc, char **argv)
{
    if(argc != 3) { cout<<"Usage: "<    
    FILE *_inFile = fopen(argv[1], "r+b"); if(_inFile == 0) { cout<<"Cannot open input file "<    FILE *_outFile = fopen(argv[2], "w+b"); 
    if(_outFile == 0)
    {
        cout<<"Cannot open output file "<        fclose(_inFile);
        return enFileOpenError;
    }
    char *_buffer[1024];
    while(!feof(_inFile) fwrite(_buffer, fread(_buffer, sizeof(_buffer), 1, _inFile), 1, _outFile);
    fclose(_inFile); fclose(_outFile);
    return enSuccess;
}