C++ STL string

#include <iostream>
#include <string>
using namespace std;


int main(int argc,char * argv[]){
string filename,basename,extname,tmpname;
const string suffix("tmp");
for(int i=1;i<argc;++i){
filename = argv[i];
string::size_type idx = filename.find('.');


if(idx == string::npos){
tmpname = filename +'.'+suffix;
       
}
else
{
basename = filename.substr(0,idx);
extname = filename.substr(idx+1);


if(extname.empty()){
tmpname = filename;
tmpname +=suffix;
}
else if(extname == suffix)
{
tmpname = filename;
tmpname.replace(idx+1,extname.size(),"xxx");
}
else{
tmpname = filename;
tmpname.replace(idx+1,string::npos,suffix);
}
}
cout<<filename<<"=>"<<tmpname<<endl;
}

return 1;

}

编译后输出：

prog.dat=>prog.tmp
mydir=>mydir.tmp
hello.=>hello.tmp
oops.tmp=>oops.xxx
end.dat=>end.tmp