I am trying to read through a file and get specific strings on each line. The end of the string that i need is marked by a semicolon. I have no problems doing this, but I am noticing that getline() with the delimiter is automatically attaching a new line to my string.
filename.open(FileName);
while(filename)
{
getline(filename, name[counter], ';');
filename >> amount[counter] >> unit[counter] >> calories[counter];
counter++;
}
So when i would go to print out the name array there would be 1 extra line break that I had not put there myself as if there was an extra '\n' being picked up along the way. Does anyone have a solution? An example of the file format that I am reading from is below.
Dave Jones; 24 Tall
Jillian Jones; 34 Short
etc...
After running
filename >> amount[counter] >> unit[counter] >> calories[counter];
the newline is still in the buffer. This normally isn't a problem when you are using only ">>"; it just ignores newlines. But when you mix getline and ">>" you need to ignore the newlines that ">>" leaves behind. Try something like this:
filename >> amount[counter] >> unit[counter] >> calories[counter];
// Ignore first character or everything up to the next newline,
// whichever comes first
filename.ignore(1, '\n');
This is a bit redundant, but it's easy to read.
Better way would be to read file line by line into a buffer and then split strings by ';':
while(true) {
std::string line;
std::getline( in, line );
if( !in ) break;
std::istringstream iline( line );
while(true) {
std::string str;
std::getline( iline, str, ';' );
if( !iline ) break;
// you get string by string in str here
}
}
A simpler way to swallow the whitespace:
filename >> amount[counter] >> unit[counter] >> calories[counter] >> std::ws;
Related
just to understand how to read correctly, how could i read the next text from file, if i want to read the diferent strings in each line. Each line can have different sizes (1st line could have 3 strings and 2nd line could have 100 strings)
2 //Number of lines
A AS BPST TRRER
B AS BP
I tried in my code something like this, but i dont know how to check if program it's in the end of line.
ifstream fich("thefile.txt");
fich >> aux; //Contain number of line
for(int i=0;i<aux;i++){ //For each line
string line;
getline(fich, line);
char nt; //First in line it's always a char
fich >> nt;
string aux;
while(line != "\n"){ //This is wrong, what expression should i use to check?
fich >> aux;
//In each read i'll save the string in set
}
}
So at the end, i want that set contains: {{A,AS,BPST,TRRER} {B,AS,BP}}
Thanks.
while(line != "\n"){ //This is wrong, what expression should i use to check?
Yes, because the '\n' was removed by the getline() function.
Using std::istringstream it is easy to parse an arbitrary number of words up to the end of the current line:
string aux;
std::istringstream iss(line);
while(iss >> aux) {
// ...
}
Also note:
fich >> aux; //Contain number of line
will leave you with an empty line read with std::getline() because in this case the '\n' will be leftover from that operation (see Using getline(cin, s) after cin for more detailed information).
I'm doing an exercise for the college and I have to compare a string added including the header <string>, and a character.
I have a text file with a few lines of data from a census, like
Alabama AL 4849377 Alaska AK 736732 Arizona AZ 6731484
I want to read the state name of each line with a string variable, but the comparison is the only thing that I am asking for, because is where I have the error.
I have this fragment of code:
struct Census{
string name;
int population, code;
};
struct States{
Census state;
};
typedef States Vector[US_STATES];
void loadCensus(ifstream & census, Vector stats){
int i=0;
string readData;
string line;
while (getline(census, line)) {
stringstream linestream(line);
while (linestream >> readData) {
if (linestream >> stats[i].state.name >>
stats[i].state.code >>
stats[i].state.population)
{
std::cerr << "Bad input on line " << i << ": " << line << std::endl;
}
stats[i].state.name=readData;
stats[i].state.code=readData;
stats[i].state.population=readData;
i++;
}
}
}
How I should convert readData to an integer to assign stats[i].state.population=readData?
I get an error in line 17 in the linestream >> readData.
You want to use the getline() function instead.
I think ita a member function of ifstream or either compare the not readData to a string ("\n") - double quotation. Or put the read data into a string and check if the sting contains a '\n'.
census >> readData will read the next word (any group of non-whitespace characters) from the input. In order to do this, it will discard all whitespace on its hunt for the next word. '\n' is whitespace, so you will never read it with the >> operator without playing games you probably don't want to play.
Instead of >>, use std::getline to read a line and then use a std::stringstream to break the line up into words.
std::string line;
while (std::getline(census, line)) {
std::stringgstream linestream(line);
while (linestream >> readData) {
statistics.state[i]=readData;
i++;
}
}
But...
I do not believe statistics.state[i]=readData; does quite what you want to do. You probably want something more like:
std::string line;
while (std::getline(census, line)) {
std::stringstream linestream(line);
if (!(linestream >> statistics.state[i].name >>
statistics.state[i].abbreviation >>
statistics.state[i].population))
{
std::cerr << "Bad input on line " << i << ": " << line << std::endl;
}
i++;
}
In this state becomes an array or vector of objects that probably looks something like
struct statestats
{
std::string name;
std::string abbreviation;
int population;
};
Breaking it down line by line
std::stringstream linestream(line);
Makes a stringstream. A string stream is a stream like cin and cout or a fstream, but it contains a string. The main use is to buffer and build strings with the same syntax you would use on another stream. In this case we are use it to split up the line into words.
if (linestream >> statistics.state[i].name >>
statistics.state[i].abbreviation >>
statistics.state[i].population)
Needs to be handled in a few parts in a few parts. Over all it is an abbreviation of
if (linestream >> statistics.state[i].name &&
linestream >> statistics.state[i].abbreviation &&
linestream >> statistics.state[i].population)
Each stage of which reads from the linestream into a variable.
Next, the >> operator returns the stream being read, and this is used two ways in the example. The first allows chaining. The output of one >> is used as the input of the next, so if you look at >> as you would a function (and it is a function. See Stream extraction and insertion for more) you can think about it looking something like this:
linestream.read(statistics.state[i].name).read(statistics.state[i].abbreviation).read(statistics.state[i].population)
The >> syntax just makes it easier.
The next advantage you get from returning the stream is the stream can be tested to see if the stream is still good. It has a boolean operator that will return true if the stream is in a good state and can be used.
if(linestream)
{
good
}
else
{
bad
}
will enter good if the stream is open, has not reached the end of the stream, and has had no troubles reading or writing data.
Going back to our example
if (linestream >> statistics.state[i].name >>
statistics.state[i].abbreviation >>
statistics.state[i].population)
Will enter the body of the if statement if the stream successfully read all three values from the stream. Which is not what we want. Ooops. I've corrected the above code already.
if (!(linestream >> statistics.state[i].name >>
statistics.state[i].abbreviation >>
statistics.state[i].population))
will enter the body of the if if at least one value was not read for any reason and print out an error message. Normally when there is an error you will need to clear the error before continuing, but in this case we've use the whole stream and are about to discard it.
Assuming no error occurred all of the data from this line has been read and there is no need to
stats[i].state.name=readData;
stats[i].state.code=readData;
stats[i].state.population=readData;
My code is working except for one problem, when I run it it doesn't seem to return the first string.
string text;
cin >> text;
getline(cin ,text);
istringstream iss(text);
copy(istream_iterator<string>(iss),
istream_iterator<string>(),
ostream_iterator<string>(cout, "\n"));
So if my input was, bf "ing" filename, it will only output:
"ing"
filename
I want it so it can output the whole line like so:
bf
"ing"
filename
Assuming you want to have the entire line printed from parsing the string passed to std::istringstream you should remove first reading a separate word, i.e., remove the line
cin >> text;
Get rid of
cin >> text; .
That one consumes the first word of your input, reads it into text, and then you discard it by overwriting text in the next line.
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');
I know about getline() but it would be nice if cin could return \n when encountered.
Any way for achieving this (or similar)?
edit (example):
string s;
while(cin>>s){
if(s == "\n")
cout<<"newline! ";
else
cout<<s<<" ";
}
input file txt:
hola, em dic pere
caram, jo també .
the end result shoud be like:
hola, em dic pere newline! caram, jo també .
If you are reading individual lines, you know that there is a newline after each read line. Well, except for the last line in the file which doesn't have to be delimited by a newline character for the read to be successful but you can detect if there is newline by checking eof(): if std::getline() was successful but eof() is set, the last line didn't contain a newline. Obviously, this requires the use of the std::string version of std::getline():
for (std::string line; std::getline(in, line); )
{
std::cout << line << (in.eof()? "": "\n");
}
This should write the stream to std::cout as it was read.
The question asked for the data to be output but with newlines converted to say "newline!". You can achieve this with:
for (std::string line; std::getline(in, line); )
{
std::cout << line << (in.eof()? "": "newline! ");
}
If you don't care about the stream being split into line but actually just want to get the entire file (including all newlines), you can just read the stream into a std::string:
std::string file((std::istreambuf_iterator<char>(in)),
std::istreambuf_iterator<char>());
Note, however, that this exact approach is probably fairly slow (although I know that it can be made fast). If you know that the file doesn't contain a certain character, you can also use std::getline() to read the entire file into a std::string:
std::getline(in, file, 0);
The above code assumes that your file doesn't contain any null characters.
A modification of #Dietmar's answer should do the trick:
for (std::string line; std::getline(in, line); )
{
std::istringstream iss(line);
for (std::string word; iss >> word; ) { std::cout << word << " "; }
if (in.eof()) { std::cout << "newline! "; }
}
Just for the record, I ended up using this (I wanted to post it 11h ago)
string s0, s1;
while(getline(cin,s0)){
istringstream is(s0);
while(is>>s1){
cout<<s1<<" ";
}
cout<<"newline! ";
}