validating user input

begin.cxx

@@ -27,22 +27,26 @@
 
 using namespace std;
 
-void begin(string needle, istream &in)
+int begin(string needle, istream &in)
 {
 	string input; //This is where we keep our input, line by line
 	boost::xpressive::sregex regex = boost::xpressive::sregex::compile( needle, boost::xpressive::regex_constants::icase ); //this is what we search for
-
-	while(in) { //loop through input line by line
-		getline(in, input);
-		if ( boost::xpressive::regex_search(input, regex) ) { //if we find a match
-			cout << input << endl; //start printing to std out
-			while(in) { //and print what remains as well
-				getline(in,input);
-				cout << input << endl;
-			}
-		}
-	}
-
+	if( !in.good() ) { //Check if steam is ok
+		cerr << "Could not open file \n";
+		return 1; //if not return 1
+	} else { //go ahead
+		while(in) { //loop through input line by line
+			getline(in, input);
+			if ( boost::xpressive::regex_search(input, regex) ) { //if we find a match
+				cout << input << endl; //start printing to std out
+				while(in) { //and print what remains as well
+					getline(in,input);
+					cout << input << endl;
+				} //end of inner while
+			} //end of if
+		} //end of outer while
+	} //end of else
+	return 0;
 }
 
 

begin.hpp

@@ -27,6 +27,6 @@
 
 using namespace std;
 
-void begin(string needle, istream &in);
+int begin(string needle, istream &in);
 
 #endif

main.cxx

@@ -21,20 +21,24 @@
 
 
 #include <iostream>
+#include <string>
 #include "begin.hpp"
 using namespace std;
 
 int main(int argc, char **argv)
 {
+	int works = 1; //default return value
 	
 	if( argc == 2) { //assume the argument is a regex and to read from std in
-		begin(argv[1], cin);
+		works = begin(argv[1], cin); //try the search
 	} else if( argc == 3) { //assume the first argument is a regex and second is a filename
 		ifstream in(argv[2]);
-		begin(argv[1], in);
-	} else {
-		cout << "Usage: begin <regex> [filename] \n";
+		works = begin(argv[1], in); //try the search
+	} else { //Wrong number of command line args
+		cout <<  "Usage: begin <regex> [filename] \n";
 	}
-	return 0;
+
+	return works;
+
 }