How should I read lines with spaces from a file.txt and record it in my vector?
I have a line that consists of many words ,but my loop doesn't see that and read them one by one and print in that way:
For example,I have a string in a file:
Hello, my friends,how are you?
Hello,James, we are fine.
And in my console, I see:
Hello,
my
friends
....
fine
This my loop:
while(rRecord»str)
{
lines.push_back(str);
}
And my function that prints my words:
void printRecord(int& numStr,struct winsize w,std::vector<std::string>& lines)
{
for (int i = numStr; i < numStr + w.winsize::ws_row-1; i++)
{
if (i>=lines.size())
break;
else
std::cout « lines[i] « std::endl;
}
numStr += w.winsize::ws_row;
}
To read line-by-line, use std::getline, like this:
std::string line;
while (std::getline(inFile, line)) {
lineVector.push_back(std::move(line));
}
The std::move means that when the vector creates the new element, it can "steal" the internal buffer from line, meaning line will now be an empty string, but saves an extra allocation+copy.
Be aware that mixing getline with >> is usually not a good idea, because >> will leave any trailing whitespace, including a newline, in the stream, meaning you get unexpected results the next time you try to getline.
Related
I'm struggling to find a way to both read a file to the end of a line, such as
dog \n
cat \n
pig
and store the char of each to an array. While I can do this for one line, I can't work out how to move on to the next line (ie dog to cat) and still register the end of the file.
Here is my code so far;
searchFile.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
char next;
while (searchFile.get(next))
{
if (next == '\n') // If the file has been opened in
{
for (int i = 0; i <= searchTempSize; i++) // ... For each character within the total length of the string ...
{
searchCharArray[i] = searchArray[i];
cout << searchCharArray[i] << endl;
}
}
}
Edit for clarity: I need to read the file and store the characters of each word as an array. However, the file contains each word on a new line. I can't seem to find a way to read on to the next line, rather than end.
The conventional way to do this is with std::getline. This returns a reference to the stream; when casted to a boolean, this indicates whether the last operation on the stream was successful, e.g., non–end-of-file. So to load all lines into an array of strings, for example, you might do the following:
std::string line;
std::vector<string> lines;
while (std::getline(searchFile, line)) {
lines.push_back(line);
}
I have read a CSV file that has line ending character as '\r', the reading operation done successfully, but the problem started when i pass the read line in to the while(getline(ss,arr2,',')) for separating comma..it does work properly for the first line but all the next iterations are empty(i.e)it has been failing to separate the comma in the string.
int main()
{
cout<<"Enter the file path :";
string filename;
cin>>filename;
ifstream file;
vector<string>arr;
string line,var;
stringstream content;
file.open(filename.c_str(),ios::in );
line.assign((std::istreambuf_iterator<char>(file)),
std::istreambuf_iterator<char>());
file.close();
string arr2;
stringstream ss;
content<<line;
//sqlite3 *db;int rc;sqlite3_stmt * stmt;
int i=0;
while (getline(content,var,'\r'))
{
ss.str(var);//for each read the ss contains single line which i could print it out.
cout<<ss.str()<<endl;
while(getline(ss,arr2,','))//here the first line is neatly separated and pushed into vector but it fail to separate second and further lines i was really puzzled about this behaviour.
{
arr.push_back(arr2);
}
ss.str("");
var="";
arr2="";
for(int i=0;i<arr.size();i++)
{
cout<<arr[i]<<endl;
}
arr.clear();
}
getch();
}
what went wrong in the above...I see nothing right now:(
The stringstream::str method does not reset / clear the internal state of the stream. After the first line, the internal state of ss is EOF (ss.eof() returns true).
Either use a local variable inside the while loop:
while (getline(content,var,'\r'))
{
stringstream ss(var);
Or clear the stream before ss.str:
ss.clear();
ss.str(var);
Basically I first takes an integer as input and then test case follows. My each test case is an string. I am suppose to print the string back if the starting patten of string matches "HI A" and it is case-insensitive. I wrote the code below to accomplish to this. My problem is that when I press enter after each input, getline takes newline character as new input. I have tried to tackle this by using extra getline after each input but the issue is still there. Program gets stuck in the loop even though I have put a break condition. What am I doing wrong?
#include <iostream>
#include <string>
using namespace std;
int main(){
int N;
cin >>N;
string nl;
getline(cin,nl);
for (int i=0;i<N;i++){
string s;
getline(cin,s);
//cout <<"string"<<s<<endl;
int flag=0;
if ((s.at(0)=='h'||s.at(0)=='H')&&(s.at(1)=='i'||s.at(1)=='I')&&(s.at(2)==' ')&&(s.at(3)=='a'||s.at(3)=='A')) flag=1;
if (flag==1) cout << s;
//cout << "not " <<s;
string ne;
cout << "i="<< i<<endl;
if (i==N-1) {break;}
getline(cin,ne);
}
}
Here is sample input:
5
Hi Alex how are you doing
hI dave how are you doing
Good by Alex
hidden agenda
Alex greeted Martha by saying Hi Martha
Output should be:
Hi Alex how are you doing
ignore() function does the trick. By default, it discards all the input suquences till new line character.
Other dilimiters and char limit can be specified as well.
http://www.cplusplus.com/reference/istream/istream/ignore/
In your case it goes like this.
cin >> N;
cin.ignore();
Your cin >>N stops at the first non-numeric character, which is the newline. This you have a getline to read past it, that's good.
Each additional getline after that reads the entire line, including the newline at the end. By putting in a second getline you're skipping half your input.
So, your real problem isn't that getline eats newlines, but that your second getline(cin, ne) is eating a line...
And that is because you mistakenly think that you need two getline operations to read one line - or something like that. Mixing "linebased" and "itembased" input does have confusing ways to deal with newlines, so you do need something to "skip" the newline left behind frin cin >> N;, but once you have got rid of that, you only need ONE getline to read up and including the newline at the end of a line.
I am writing this answer with the hopes that it may help someone else out there that wants a very simple solution to this problem.
In my case the problem was due to some files having different line endings such as '\r' vs. '\n'. Everything worked fine in windows but then it failed in Linux.
The answer was actually simple. I created a function removeNewLineChar after each line was read in. That way the char was removed. The removeNewLineChar takes in the line that was read in and copies it over character by character into a new string but it avoids copying either of the newline characters.
Here is an example:
string trim(string line)
{
string newString;
for (char ch : line)
{
if (ch == '\n' || ch == '\r')
continue;
newString += ch;
}
return newString;
}
//some function reading a file
while (getline(fin, line)) {
line = trim(line);
//... do something with the line
line = "";
}
you just need to accept the fact that getline will give you '\n' at the end. One solution is remove '\n' after getting it. Another solution is do not write the additional 'endl'. for example, for your problem, you can use this code
int N;
cin >> N;
string line;
getline(cin, line); // skip the first new line after N.
for (int i = 0; i < N; i++) {
string line;
getline(cin, line);
string first4 = line.substr(0, 4);
// convert to upper case.
std::transform(first4.begin(), first4.end(), first4.begin(), std::ptr_fun<int, int>(std::toupper)); // see http://en.cppreference.com/w/cpp/algorithm/transform
if (first4 == "HI A") {
cout << line; // do not include "<< endl"
}
}
cin.ignore() worked for me.
void House::provideRoomName()
{
int noOfRooms;
cout<<"Enter the number of Rooms::";
cin>>noOfRooms;
cout<<endl;
cout<<"Enter name of the Rooms::"<<endl;
cin.ignore();
for(int i=1; i<=noOfRooms; i++)
{
std::string l_roomName;
cout<<"Room"<<"["<<i<<"] Name::";
std::getline(std::cin, l_roomName);
}
}
std::string line;
std::cin>>std::ws; // discard new line not processed by cin
std::getline(std::cin,line);
From Notes section https://en.cppreference.com/w/cpp/string/basic_string/getline
When consuming whitespace-delimited input (e.g. int n; std::cin >> n;) any whitespace that follows, including a newline character, will be left on the input stream. Then when switching to line-oriented input, the first line retrieved with getline will be just that whitespace. In the likely case that this is unwanted behaviour, possible solutions include:
An explicit extraneous initial call to getline
Removing consecutive whitespace with std::cin >> std::ws
Ignoring all leftover characters on the line of input with cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
For example, when parsing a text file, some times this file have stuff like this:
keyword a string here
keyword another string
keyword
keyword again a string
Note that the 3th line have an empty string (nothing or white spaces).. The thing is that when you do stringstream>>laststring, and stringstream have an empty string (null or just white space), it will not overwrite the "laststring", it will do nothing. Theres anyway to check this situation before hand? I dont want to create a temp empty string just to check it is still empty after stringstream>>, seems lame.
When you cannot read from stream - its state changes, so when casting to bool, it returns false:
bool read = static_cast<bool>(ss >> laststring);
Or - in if-expr:
if (ss >> laststring)
cout << "Just read: " << laststring;
See example
You can only know after trying to read whether there was something or not. What you might be able to do is to skip whitespace and see if there is a non-space in the next location:
if ((in >> std::ws).peek() != std::char_traits<char>::eof()) {
...
}
Given that empty strings are cheap to create, I wouldn't bother and try read the string. Note, however, that reading from streams isn't line based, i.e., in your case above you need to split the lines first or use something like std::getline() to read the second part of line.
You can use getline, to read a line from the file. Then, copy the line into a string stream and read words from the string stream one at a time. The streams will automatically stop reading when they run out of lines / words.
// open file
std::ifstream fin("text.txt");
// 'iterate' through all the lines in the file
unsigned lineCount = 1;
std::string line;
while (std::getline(fin, line))
{
// print the line number for debugging
std::cout << "Line " << lineCount << '\n';
// copy line into another stream
std::stringstream lineStream(line);
// 'iterate' through all the words in the line
unsigned wordCount = 1;
std::string word;
while (lineStream >> word)
{
// print the words for debugging
std::cout << '\t' << wordCount++ << ' ' << word << '\n';
}
}
You need to include iostream, fstream, sstream and string.
For checking if string is empty, use foo.size() == 0.
For checking if string stream is empty fooStream.rdbuf()->in_avail() == 0
I am reading from a file and passing the front of the array(pointer) back into my main function. The problem I am having is that it is not copying the blank spaces in between the words. For example Hello Hello comes out as HelloHello.
I started by using getLine instead and ran into the problems of size of the file. I set it to 500 because no files will be larger than 500, however most files will be below 500 and I am trying to get the exact size of the file.
Here is my code:
char infile()
{
const int SIZE=500;
char input[SIZE];
char fromFile;
int i=0;
ifstream readFile;
readFile .open("text.txt");
while(readFile>>fromFile)
{
input[i]=fromFile;
i++;
}
cout<<endl;
returnArray=new char[i];//memory leak need to solve later
for(int j=0;j<i;j++)
{
returnArray[j]=input[j];
cout<<returnArray[j];
}
cout<<endl;
}
return returnArray[0];
}
Depending on what your file format is, you may want to use ifstream::read() or ifstream::getline() instead.
operator >> will attempt to 'tokenize' or 'parse' the data stream as it is being read, using whitespace as separators between tokens. You're interested in getting the raw data from the file with whitespace intact, therefore you should avoid using it. If you want to read data in one line at a time, using linefeeds as separators, you should use getline(). Otherwise use read().
Use std::string, std::vector and std::getline and you can still return a char. That will solve your memory leak and skipping whitespace problem.
Example:
char infile()
{
std::ifstream readFile("text.txt");
std::vector<std::string> v;
std::string line;
while(std::getline(readFile, line))
{
v.push_back(line);
}
for(auto& s : v)
{
std::cout << s << std::endl;
}
return (v[0])[0];
}
You are asking it to read while delimiting where there is whitespace.
You can use getline() to preserve the whitespace.