C++ Programming Code Examples
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Use get() and getline() to read characters.
/* Use get() and getline() to read characters. */
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
char ch;
char str[256];
ofstream fout("test.dat");
if(!fout) {
cout << "Cannot open file for output.\n";
return 1;
}
fout << "This is a line of text.\n";
fout << "This is another line of text.\n";
fout << "This is the last line of text.\n";
fout.close();
if(!fout.good()) {
cout << "An error occurred when writing to the file.\n";
return 1;
}
ifstream fin("test.dat", ios::in);
if(!fin) {
cout << "Cannot open file for input.\n";
return 1;
}
cout << "Use get():\n";
cout << "Here are the first three characters: ";
for(int i=0; i < 3; ++i) {
fin.get(ch);
cout << ch;
}
cout << endl;
fin.get(str, 255);
cout << "Here is the rest of the first line: ";
cout << str << endl;
fin.get(ch);
cout << "\nNow use getline():\n";
fin.getline(str, 255);
cout << str << endl;
fin.getline(str, 255);
cout << str;
fin.close();
if(!fin.good()) {
cout << "Error occurred while reading or closing the file.\n";
return 1;
}
return 0;
}
Get line from stream into string. The cin is an object which is used to take input from the user but does not allow to take the input in multiple lines. To accept the multiple lines, we use the getline() function. It is a pre-defined function defined in a <string.h> header file used to accept a line or a string from the input stream until the delimiting character is encountered. Extracts characters from is and stores them into str until the delimitation character delim is found (or the newline character, '\n', for (2)). The extraction also stops if the end of file is reached in is or if some other error occurs during the input operation. If the delimiter is found, it is extracted and discarded (i.e. it is not stored and the next input operation will begin after it).
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Check whether state of stream is good. Returns true if none of the stream's error state flags (eofbit, failbit and badbit) is set. ios::good() and ios::bad() functions in C++ are used to check the state of the stream whether it is good or bad to do our task. Both of these are defined in ios library. The good() method of ios class in C++ is used to check if the stream is good enough to work. It means that this function will check if this stream has raised any error or not. Notice that this function is not the exact opposite of member bad, which only checks whether the badbit flag is set. This function does not accept any parameter. Function returns true if none of the stream's state flags are set.
Get characters. Extracts characters from the stream, as unformatted input. The get() function is used to read a character(at a time) from a file. The classes istream and ostream define two member functions get(), put() respectively to handle the single character input/output operations. There are two types of get() functions. Both get(char *) and get(void) prototype can be used to fetch a character including the blank space,tab and newline character. The get(char *) version assigns the input character to its argument and the get(void) version returns the input character. Since these functions are members of input/output Stream classes, these must be invoked using appropriate objects.
