string substitution

  char* usr = getlogin() ;
  ifstream in("/var/mail/   <output here>  ") ;

I want to substitute the output of getlogin() in the above ifstream, how shoud i, helps please
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char* usr = getlogin();
char* basepath="/var/mail";
char* filename = new char[strlen(usr)+strlen(basepath)+1];
strcpy(filename, basepath);
strcat(filename, usr);
ifstream in(filename);

// === or ===
std::string usr(getlogin());
ifstream in((std::string("/var/mail/") + usr).c_str())

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I strongly recommend the 2nd approach, but would change it to

std::string FilNam  = "/var/mail/";
FilNam += getlogin();
ifstream in(FilNam.c_str());

for readability.
beginAuthor Commented:
thanks for your solutions.
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