C++ Tutorial/File Stream/Text file read
Версия от 14:21, 25 мая 2010; (обсуждение)
Содержание
file input with strings
#include <fstream>
#include <iostream>
using namespace std;
int main(){
const int MAX = 80;
char buffer[MAX];
ifstream infile("TEST.TXT");
while( !infile.eof() ){
infile.getline(buffer, MAX);
cout << buffer << endl;
}
return 0;
}Read a text file line by line
#include <fstream>
#include <iostream>
using namespace std;
int main ()
{
char buffer[256];
ifstream myfile ("test.txt");
while (! myfile.eof() )
{
myfile.getline (buffer,100);
cout << buffer << endl;
}
return 0;
}10 123.23 This is a text.
Read from file
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
char ch;
int i;
float f;
char str[80];
ofstream out("test.txt");
if(!out) {
cout << "Cannot open file.\n";
return 1;
}
out << 10 << " " << 123.23 << "\n";
out << "This is a text.";
out.close();
ifstream in("test.txt");
if(!in) {
cout << "Cannot open file.\n";
return 1;
}
in >> i;
in >> f;
in >> ch;
in >> str;
cout << i << " " << f << " " << ch << "\n";
cout << str;
in.close();
return 0;
}10 123.23 T his
Reading and Writing Text Files
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ofstream out("INVNTRY"); // output, normal file
if(!out) {
cout << "Cannot open INVENTORY file.\n";
return 1;
}
out << "Radios " << 39.95 << endl;
out << "Toasters " << 19.95 << endl;
out << "Mixers " << 24.80 << endl;
out.close();
return 0;
}Read integer from a text file
#include <fstream>
#include <iostream>
#include <vector>
#include <string>
#include <stdexcept>
using namespace std;
void readIntegerFile(const string& fileName, vector<int>& dest)throw (invalid_argument, runtime_error)
{
ifstream istr;
int temp;
istr.open(fileName.c_str());
if (istr.fail()) {
string error = "Unable to open file " + fileName;
throw invalid_argument(error);
}
while (istr >> temp) {
dest.push_back(temp);
}
if (istr.eof()) {
istr.close();
} else {
istr.close();
string error = "Unable to read file " + fileName;
throw runtime_error(error);
}
}
int main(int argc, char** argv)
{
vector<int> myInts;
const string fileName = "test.txt";
try {
readIntegerFile(fileName, myInts);
} catch (const invalid_argument& e) {
cerr << e.what() << endl;
exit (1);
} catch (const runtime_error& e) {
cerr << e.what() << endl;
exit (1);
}
for (unsigned int i = 0; i < myInts.size(); i++) {
cout << myInts[i] << " ";
}
cout << endl;
return (0);
}Read string and float value from a file
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ofstream out("test.txt"); // output, normal file
if(!out) {
cout << "Cannot open test.txt file.\n";
return 1;
}
out << "R " << 9.9 << endl;
out << "T " << 9.9 << endl;
out << "M " << 4.8 << endl;
out.close();
ifstream in("test.txt"); // input
if(!in) {
cout << "Cannot open test.txt file.\n";
return 1;
}
char item[20];
float cost;
in >> item >> cost;
cout << item << " " << cost << "\n";
in >> item >> cost;
cout << item << " " << cost << "\n";
in >> item >> cost;
cout << item << " " << cost << "\n";
in.close();
return 0;
}R 9.9 T 9.9 M 4.8
Read text file line by line
#include <iostream>
#include <fstream>
using namespace std;
int main(int argc, char *argv[]){
ifstream in("text.txt");
if(!in){
cout << "Cannot open file.";
exit (1);
}
char str[255];
while(in){
in.getline(str, 255); // Delimiter defaults to newline
cout << str << endl;
}
in.close();
}Read text file token by token
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
ifstream inFile("test.cpp");
if (inFile.fail()) {
cerr << "Unable to open file for reading." << endl;
exit(1);
}
string nextToken;
while (inFile >> nextToken) {
cout << "Token: " << nextToken << endl;
}
inFile.close();
return 0;
}