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).
Related
I have a csv that I'd like to tokenize line by line with StringStream. The key is that I know apriori what the columns would look like. For example, say I know the file looks like the following
StrHeader,IntHeader
abc,123
xyz,456
I know ahead of time it is a string column, followed by an int column.
Common approach is to read the file line by line
std::string line;
stringstream lineStream;
while (getline(infile, line)) // read line by line
{
cout << "line " << line << endl;
lineStream << line;
string token;
while(getline(lineStream, token, ',')) // push into vector? this is not ideal
{
}
I know I can have 2 loops, and have inner loop tokenizes the string based on commas. Lots of sample code on stackoverflow would store the result into a vector<string>.
I don't want to do create a new vector every line. Since I know apriori what columns the file would have, can I somehow read directly into a string and int variable? Like this
std::string line;
stringstream lineStream;
while (getline(infile, line)) // read line by line
{
cout << "line " << line << endl;
lineStream << line; // DOESNT WORK - tell lineStream we have comma delimited string
string strValue;
int intValue;
lineStream >> strValue >> intValue; // SO MUCH CLEANER
// call foo(strValue, intValue);
}
The problem above is this line
lineStream << line; // DOESNT WORK - tell lineStream we have comma delimited string
From what I could tell, the above code works if the input line is space delimited, not comma delimited.
I have no control over the input. So, simply replacing the "spaces" with "commas" in the original string is not an ideal solution since I don't know if the input already has spaces.
Any ideas? thanks
You could try to only read to the delimiter with std::getline() and then put that in a string stream for conversion.
while (!infile.eof()){
std::getline(infile, strValue, ',');
std::getline(infile, line);
strstr.str(line);
strstr.clear();
int intValue;
strstr >> intValue;
foo(strValue, intValue);
}
I want to read in scores from a txt file. The scores are going into a struct.
struct playerScore
{
char name[32];
int score, difficulty;
float time;
};
the text file looks like this
Seth 26.255 40 7
as one line, where each item is followed by a tab. (Name\t time\t score\t difficulty\n)
When I begin to read in the text, I don't know how to tell the program when to stop. The scores file could be any number of lines or score entries. This is what I have attempted.
hs.open("scores.txt", ios_base::in);
hs.seekg(0, hs.beg);
if (hs.is_open())
{
int currpos = 0;
while (int(hs.tellg()) != int(hs.end));
{
hs>> inScore.name;
hs >> inScore.time;
hs >> inScore.score;
hs >> inScore.difficulty;
hs.ignore(INT_MAX, '\n');
AllScores.push_back(inScore);
currpos = (int)hs.tellg();
}
}
I'm trying to make a loop that will read in a line of code into a temp struct for the data, then push that struct into a vector of structs. Then update the currpos variable with the current location of the input pointer. However, the loop just gets stuck on the condition and freezes.
There are a multitude of ways to do this, but the following is likely what you're looking for. Declare a free-operator for extracting a single-line definition of a player-score:
std::istream& operator >>(std::istream& inf, playerScore& ps)
{
// read a single line.
std::string line;
if (std::getline(inf, line))
{
// use a string stream to parse line by line.
std::istringstream iss(line);
if (!(iss.getline(ps.name, sizeof(ps.name)/sizeof(*ps.name), '\t') &&
(iss >> ps.time >> ps.score >> ps.difficulty)))
{
// fails to parse a full record. set the top-stream fail-bit.
inf.setstate(std::ios::failbit);
}
}
return inf;
}
With that, your read code can now do this:
std::istream_iterator<playerScore> hs_it(hs), hs_eof;
std::vector<playerScore> scores(hs_it, hs_eof);
I dont think that you can just >> from your file. Do you think it will take everything till \t? :)
You can try to take for example token with strtok()
I guess it can use '\t' to split string and take for each variable via this function needed part of string
In case if it strtok() doesnt work that way i guess you can just copy till '\t' in sub-loop
You can do like this
playerScore s1;
fstream file;
file.open("scores.txt", ios::in | ios::out);
while(!file.eof()) //For end of while loop
{
file.read(s1, sizeof(playerScore));//read data in one structure.
AllScores.push_back(s1);
}
I'm trying to read a file word by word and do some implementation on each word. In future I want to know where was the position of each word. Position is line number and character position in that line. If character position is not available I only need to know when I'm reading a file when I go to the next line. This is the sample code I have now:
string tmp;
while(fin>>tmp){
mylist.push_back(tmp);
}
I need to know when fin is going to next line?!
"I need to know when fin is going to next line"
This is not possible with stream's operator >>. You can read the input line by line and process each line separately using temporary istringstream object:
std::string line, word;
while (std::getline(fin, line)) {
// skip empty lines:
if (line.empty()) continue;
std::istringstream lineStream(line);
for (int wordPos = 0; lineStream >> word; wordPos++) {
...
mylist.push_back(word);
}
}
just don't forget to #include <sstream>
One simple way to solve this problem would be using std::getline, run your own counter, and split line's content into words using an additional string stream, like this:
string line;
int line_number = 0;
for (;;) {
if (!getline(fin, line)) {
break;
}
istringstream iss(line);
string tmp;
while (iss >> tmp) {
mylist.push_back(tmp);
}
line_number++;
}
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 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;