I am working on a program in c++ and I need to read an entire string of text from a file. The file contains an address on one of the lines like this "123 Easy Ave" this has to be pulled into one string or char. Here is the code I have:
The data file:
Matt Harrold
307C Meshel Hall
1000 .01 4
The data is made up of a first and last name which become CustomerName, the next line is the address which is to populate Address, Then three numbers: principle, InterestRate, Years.
The code:
float InterestRate = 0;
int Years = 0;
char Junk [20];
int FutureValue;
float OnePlusInterestRate;
int YearNumber;
int count = 0;
char CustomerName;
string Address;
int * YearsPointer;
CustomerFile >> CustomerName
>> Address
>> Principle
>> InterestRate
>> Years;
Right now it only pulls in "103C" and stops at the space... Help is greatly appreciated!
Edit: In response to feedback on my question, I have edited it to use the more appropriate std::getline instead of std::istream::getline. Both of these would suffice, but std::getline is better suited for std::strings and you don't have to worry about specifying the string size.
Use std::getline() from <string>.
There is a good reference and example here: http://www.cplusplus.com/reference/string/getline/.
You'll also need to be careful combining the extraction (>>) operator and getline. The top answer to this question (cin>> not work with getline()) explains briefly why they shouldn't be used together. In short, a call to cin >> (or whatever input stream you are using) leaves a newline in the stream, which is then picked up by getline, giving you an empty string. If you really want to use them together, you have to call std::istream::ignore in between the two calls.
use std::getline from the <string> header.
Related
I am new to C++ and I am reading in a text file. The content of text file is like:
$ (first line)
2 (second)
MY NAME IS (whatever sentence with 10 or below characters)(third)
12 21 (forth)
22 22 (fifth)
221 (sixth)
fly jump run (seventh)
fish animal (eighth)
So I need to read all of these and store them into different variables line by line and so far I'd manage to store them into string array line by line but how can I store the numbers like 12 21 in forth line into 2 different integer variables such as int b and int c?
and also like last two line
how can I store the fly jump run fish animal into 5 different string variables respectively?
Basically Now I am putting them into a string array line by line and trying to access them and take them out of the array and store it.
if (file.is_open()){
cout<<"Congratulations! Your file was successfully read!";
while (!file.eof()){
getline(file,line);
txt[i]=line;
i++;
}
}
Just want to store every line into variables based on their data type.
The streams support streaming the content directly into the basic data types (int, double etc.). So the istream::operator>>(int&) does the work for you.
The below small sample class demonstrates it by reading your sample file into the members -- hope that helps:
class Creature
{
public:
void read(istream& stream)
{
string line;
stream.ignore(10, '\n'); // skip line 1 (= $)
stream >> m_integers[0]; // line 2 = single int
stream.ignore(1, '\n'); // skip end of line
getline(stream, m_sentence); // get the full sentence line ..
// and the rest ... we can read that in a single code line ...
stream >> m_integers[1] >> m_integers[2] >> m_integers[3] >> m_integers[4]
>> m_integers[5] >> m_whatCanIdDo[0] >> m_whatCanIdDo[1] >> m_whatCanIdDo[2] >> m_whatIAm[0] >> m_whatIAm[1];
}
private:
string m_sentence;
int m_integers[6];
string m_whatCanIdDo[3];
string m_whatIAm[2];
};
Calling the function:
int main()
{
ifstream file;
file.open("creature.txt");
Creature cr;
cr.read(file);
file.close();
}
There are several ways of doing this, but one of the most straightforward is to use a stringstream.
To do this, copy the lines you want to tokenize from your txt array into a stringstream. Use the stream extratction operator (>>) to read out each word from that line, separated by a space, into a separate variable.
//Required headers
#include <string>
#include <sstream>
...
string word1, word2;
stringstream words(txt[lineNumber]);
words >> word1 >> word2;
//Process words
For each line you tokenize, you'll have to reset the stream.
//Read in next line
lineNumber++;
//Reset stream flags
words.clear();
//Replace the stream's input string
words.str(txt[lineNumber]);
words >> word1 >> word2;
//Process new words
You can use the same process for both integers and strings. The stream extraction operator will automatically convert strings to whatever data type you give it. However, it's up to you to make sure that the data it's trying to convert is the correct type. If you try to write a string to an int using a stringstream, the stringstream will set a fail bit and you won't get any useful output.
It's a good idea to write your input to a string, and then check whether that string is, in fact, a number, before trying to write it to an integer. But that's an entirely different topic, there are many ways to do it, and there are several other questions on this site that cover it.
I have a problem with my code in C++ and need some help. There are some related questions but I couldn't really understand the answers.
I have a text file ('parameters.dat' in the example below) that I want to read in with my code written in C++. The file includes different types of variables: Boolean, doubles and integers as well as some comments which I want to skip when reading.
My file looks something like that:
150 // this is an integer
4e-1 // this is a double
1.05 // another double
0 // this is a logical (Boolean) variable: 0 is false and 1 is true
A simple version of the code that I use is
int N;
double var_1, var_2;
bool inital;
ifstream read_parameters;
read_parameters.open("parameters.dat");
read_parameters >> N >> var_1 >> var_2 >> initial;
read_parameters.close();
The comments seem to ruin everything and even without them there seem to be some problems with reading the logical variables correctly. The file that I try to read is made by me, so I can substitute the '//' above with something else if necessary. Does anyone have any advice?
Thanks in advance!
Simple, cheesy way:
Read a token then read_parameters.ignore(numeric_limits<streamsize>::max(), '\n') to discard the rest of the line. eg:
read_parameters >> N;
read_parameters.ignore(numeric_limits<streamsize>::max(), '\n');
read_parameters >> var_1;
read_parameters.ignore(numeric_limits<streamsize>::max(), '\n');
...
This doesn't care if a comment exists or not, but requires modification if you have two or more tokens on a line.
Oh, and remember to test the state of the stream after reading. Plugging in "fubar" for one of the doubles will currently ruin things. read_parameters will be in an error state that needs to be cleared before you can read it again.
if (!read_parameters >> N)
{
std::cerr << "bad input for parameter N" << std::endl;
read_parameters.clear();
}
read_parameters.ignore(numeric_limits<streamsize>::max(), '\n');
Is better, but you probably want to handle an error with something better than a printline.
Take input in a Dynamic Character array then run a for loop in which if a character has ascii 65 - 97 - onward then it will be Alphabet and else if ascii represents integers like 1,2,3 then separte them in another array after calculating total integers as count++ .
int i = 5;
char c = 'n';
string st = "cool";
ofstream my("we.txt");
my <<st<<","<<c<<","<<i<<","<<endl;
string s;
ifstream your("we.txt");
while(your){
getline(your, st, ',');
your>>c;
your.ignore(1);
your>>i;
your.ignore(1);
cout<<st<<","<<c<<","<<i<<endl;
}
my.close();
I don't even know what your.ignore(1) stands for, but somehow it works. The problem is that it print the result twice, why?
Can someone explain me how to handle the info that I've written in the file? If I wanted to save in a file 3 info string trade, double price and char sold (y/n), about every item I have how can I manage it?
It would look like this
Timberland, 40, n;
Gucci, 10, y; ..... etc..
I need it now, cause tomorrow I have a test, I appreciate your help, and sorry for my english!
As for the problem with the double-printing, it's because the eofbit flag is not set until after you read from beyond the end of the file. That means your loop will iterate once to many.
I suggest you instead use getline to read the complete line (in the condition of the loop), and then use e.g. std::istringstream to parse the line.
So do e.g.
while (std::getline(your, fullLine))
{
std::istringstream istr(fullLine);
getline(istr, st, ',');
istr >> c;
// etc.
}
Hey guys so I have an assignment for class where I have to split a string and manipulate it. However, when I try to split the string and assign it to an array only the first element comes and the other two don't. Please help.
#include <iostream>
#include <string>
#include <sstream>
#include <vector>
using namespace std;
int main()
{
string str;
cout<<"Enter a first name, middle initial, last name: ";
cin>> str;
string word;
string array[3];
stringstream stream(str);
int counter = 0;
while( getline(stream, word, ' ') )
{
cout<<word;
array[counter] = word;
counter++;
}
cout<<"The "<<array[0].length()<<" characters of the first name are: "<<array[0]<<endl;
cout<<"The "<<array[2].length()<<" characters of the last name are: "<<array[2]<<endl;
string newstring = array[2]+", "+array[0]+" "+array[1];
cout<<"In the phone book, the name would be: "<<newstring<<endl;
cout<<"The length of the name is: "<<newstring.length()<<endl;
cout<<"The comma is at position: "<<newstring.find(",")<<endl;
array[0].swap(array[2]);
cout<<"After the swap, the last name is "<<array[2]<<" and the first name is "<<array[0];
system("pause");
return 0;
}
There are a few blatant errors in your code:
You need to always check your input after trying to read! You do that using the while-loop but you also need to verify that you actually successfully read the string first.
It seems you are mixing the what the input operator for std::string and std::getline() are doing: the input operator reads the first word after skipping leading spaces while std::getline() read, well, a line (whether the line terminator can be specified as third argument).
When reading fixed sized array you always need to make sure you do not read more than fits into this array! You may have heart about hackers exploiting software by using buffer overruns: assuming you'd actually indeed read a line first followed by splitting it into words you'd have created one of those exploitable programs! If you don't want to check before each word if there is enough space in the array, you'd use, e.g., a std::vector<std::string> (doing so also has a problem with hackers, namely that it opens up the program for a Denial of Service attack but although this is still a problem it is a somewhat lesser problem).
There are also a few smaller issues with your program, too:
If you are only reading from a string stream, you should use std::istringstream as there is no need to also set up the writing part of the std::stringstream.
The programs asks for "first name, middle name, and last name". I would read that specification to use, e.g., "John, F., Kennedy" but it seems you'd expect "John F. Kennedy". One reason I would expect that commas are to be used is that I don't have a middle name, i.e., I would enter "Dietmar, , Kühl".
Ok, just to be up front, this IS homework, but it isn't due for another week, and I'm not entirely sure the final details of the assignment. Long story short, without knowing what concepts he'll introduce in class, I decided to take a crack at the assignment, but I've run into a problem. Part of what I need to do for the homework is read individual characters from an input file, and then, given the character's position within its containing word, repeat the character across the screen. The problem I'm having is, the words in the text file are single words, each on a different line in the file. Since I'm not sure we'll get to use <string> for this assignment, I was wondering if there is any way to identify the end of the line without using <string>.
Right now, I'm using a simple ifstream fin; to pull the chars out. I just can't figure out how to get it to recognize the end of one word and the beginning of another. For the sake of including code, the following is all that I've got so far. I was hoping it would display some sort of endl character, but it just prints all the words out run together style.
ifstream fin;
char charIn;
fin.open("Animals.dat");
fin >> charIn;
while(!fin.eof()){
cout << charIn;
fin >> charIn;
}
A few things I forgot to include originally:
I must process each character as it is input (my loop to print it out needs to run before I read in the next char and increase my counter). Also, the length of the words in 'Animals.dat' vary which keeps me from being able to just set a number of iterations. We also haven't covered fin.get() or .getline() so those are off limits as well.
Honestly, I can't imagine this is impossible, but given the restraints, if it is, I'm not too upset. I mostly thought it was a fun problem to sit on for a while.
Why not use an array of chars? You can try it as follow:
#define MAX_WORD_NUM 20
#define MAX_STR_LEN 40 //I think 40 is big enough to hold one word.
char words[MAX_WROD_NUM][MAX_STR_LEN];
Then you can input a word to the words.
cin >> words[i];
The >> operator ignores whitespace, so you'll never get the newline character. You can use c-strings (arrays of characters) even if the <string> class is not allowed:
ifstream fin;
char animal[64];
fin.open("Animals.dat");
while(fin >> animal) {
cout << animal << endl;
}
When reading characters from a c-string (which is what animal is above), the last character is always 0, sometimes represented '\0' or NULL. This is what you check for when iterating over characters in a word. For example:
c = animal[0];
for(int i = 1; c != 0 && i < 64; i++)
{
// do something with c
c = animal[i];
}