[C++]Importing text file - Problems with getline() - c++

I've been having trouble with reading text files in c++, particularly when assigning a line to a variable.
I have the following code:
ifstream fx;
fx.open(nomeFich);
if(!fx)
{cout << "FX. nao existe!" <<endl;}
string linha="";;
int pos, inic;
while(!fx.eof())
{
getline(fx,linha);
if(linha.size() > 0)
{
cout << linha << endl;
inic=0;
pos=0;
pos=linha.find(",",inic);
cout << pos << endl;
string nomeL1(linha.substr(inic,pos));
cout << "atribuiu 1" << endl;
inic=pos;
cout <<"inic: " << inic << " pos:" << pos <<endl;
pos=linha.find(',',inic);
string nomeL2(linha.substr(inic,pos));
cout << "atribuiu 2" << endl;
inic=pos;
cout <<"inic: " << inic << " pos:" << pos <<endl;
pos=linha.find(',',inic);
cout << "atribuiu 3" << endl;
string dist(linha.substr(inic,pos));
When it does the cout << linha << endl; it returns something like :
= = == = = = = == = = = = = = = == = = = = == = = = = =
I've googled it quite a lot and can't find an answer.
I'm new to C++ so don't bash too much xD

Don't do this:
while(!fx.eof())
{
getline(fx,linha); // Here you have to check if getline() actually succeded
// before you do any further processing.
// You could add if (!fx) { break;}
// STUFF;
}
But the better design is:
while(getline(fx,linha)) // If the read works then enter the loop otherwise don't
{
// STUFF
}
You are failing to move past the comma:
inic=pos; // pos is the position of the last ',' or std::string::npos
pos=linha.find(',',inic); // So here pos will be the same as last time.
// As you start searching from a position that has a comma.

ifstream has a getline function, it accepts a char* as the first parameter and the maximum length as the second.
ifstream also has operator>> which you should be using for input, but it will read till whitespace, which is not what you want.
::getline that you're using should also work, but that's assuming that the stream is OK, which as mentioned before, you don't check correctly. You should be checking for errors after calling it, because if you reach EOF or there's an error, you won't know until the whole loop is done.
Also, what's in the file? Maybe what you're getting is the correct result?

Related

C++ Trouble Modifying A String

So in this program I'm trying to go through word by word and make it only lowercase letters, no whitespace or anything else. However, my string "temp" isn't holding anything in it. Is it because of the way I'm trying to modify it? Maybe I should try using a char * instead? Sorry if this is a stupid question, I'm brand new to c++, but I've been trying to debug it for hours and can't find much searching for this.
#include <string>
#include <iostream>
#include <fstream>
#include <ctype.h>
using namespace std;
int main(int argc, char* argv[]) {
/*if (argc != 3) {
cout << "Error: wrong number of arguments." << endl;
}*/
ifstream infile(argv[1]);
//infile.open(argv[1]);
string content((std::istreambuf_iterator<char>(infile)),
(std::istreambuf_iterator<char>()));
string final;
string temp;
string distinct[5000];
int distinctnum[5000] = { 0 };
int numdist = 0;
int wordcount = 0;
int i = 0;
int j = 0;
int k = 0;
int isdistinct = 0;
int len = content.length();
//cout << "test 1" << endl;
cout << "length of string: " << len << endl;
cout << "content entered: " << content << endl;
while (i < len) {
temp.clear();
//cout << "test 2" << endl;
if (isalpha(content[i])) {
//cout << "test 3" << endl;
if (isupper(content[i])) {
//cout << "test 4" << endl;
temp[j] = tolower(content[i]);
++j;
}
else {
//cout << "test 5" << endl;
temp[j] = content[i];
++j;
}
}
else {
cout << temp << endl;
//cout << "test 6" << endl;
++wordcount;
final = final + temp;
j = 0;
for (k = 0;k < numdist;k++) {
//cout << "test 7" << endl;
if (distinct[k] == temp) {
++distinctnum[k];
isdistinct = 1;
break;
}
}
if (isdistinct == 0) {
//cout << "test 8" << endl;
distinct[numdist] = temp;
++numdist;
}
}
//cout << temp << endl;
++i;
}
cout << wordcount+1 << " words total." << endl << numdist << " distinct words." << endl;
cout << "New output: " << final << endl;
return 0;
}
You can't add to a string with operator[]. You can only modify what's already there. Since temp is created empty and routinely cleared, using [] is undefined. The string length is zero, so any indexing is out of bounds. There may be nothing there at all. Even if the program manages to survive this abuse, the string length is likely to still be zero, and operations on the string will result in nothing happening.
In keeping with what OP currently has, I see two easy options:
Treat the string the same way you would a std::vector and push_back
temp.push_back(tolower(content[i]));
or
Build up a std::stringstream
stream << tolower(content[i])
and convert the result into a string when finished
string temp = stream.str();
Either approach eliminates the need for a j counter as strings know how long they are.
However, OP can pull and endrun around this whole problem and use std::transform
std::transform(content.begin(), content.end(), content.begin(), ::tolower);
to convert the whole string in one shot and then concentrate on splitting the lower case string with substring. The colons in front of ::tolower are there to prevent confusion with other tolowers since proper namespacing of the standard library has been switched off with using namespace std;
Off topic, it looks like OP is performing a frequency count on words. Look into std::map<string, int> distinct;. You can reduce the gathering and comparison testing to
distinct[temp]++;

getline and testing EOF at once

I would like to ask about my problem I tried to read Getline and EOF Question but did not help.
Problem is I have no idea where could be mistake here:
Is there some problem with used function ( getline or checking EOF ) ?
If there is no text in text.txt file it says there something was found. But I have no idea why or where I made a mistake ...
What I want is: Search for string and if there is no text in txt file I want it to says EOF or something. It still says - even if file is empty - string I was looking for was found in line one , position one - for example
I am puting there code:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int openFile(void);
int closeFile(void);
int getTime(void);
int findTime();
int findDate();
int stringFind(string);
bool getOneLine(void);
string what;
bool ifound = false;
string foundstring;
string filename ;
fstream inputfile;
string sentence ;
size_t found ;
string foundTime ;
string foundDate ;
bool timeIsHere = false;
bool dateIsHere = false;
int iterTime = 0;
int iterDate = 0;
int line = 0;
int main (void){
sentence.clear();
cout << " Enter the file name:" << endl;
openFile();
while (getOneLine() != false) {
stringFind("Time");
}
cout << "END OF PROGRAM" << endl;
system("PAUSE");
///getTime();
closeFile();
system("PAUSE");
}
int closeFile(void) {
inputfile.close();
cout << " File: " << filename << " - was closed...";
return 0;
}
int openFile(void) {
cout << " Insert file name in program directory or full path to desired file you want to edit:"<<endl;
cout << " Do not use path with a space in directory address or filename ! " << endl;
cout<<" ";
getline(cin, filename);
inputfile.open(filename, ios::in);
cout <<" file_state: " << inputfile.fail();
if (inputfile.fail() == 1) {
cout << " - Cannot open your file" << endl;
}
else cout << " - File was openned sucesfully"<< endl;
return 0;
}
int stringFind(string what) {
cout << " I am looking for:" << what << endl;
found = what.find(sentence);
if (found == string::npos) {
cout << " I could not find this string " << endl;
}
else if(found != string::npos){
cout << " substring was found in line: " << line + 1 << " position: " << found + 1 << endl << endl;
ifound = true;
foundstring = sentence;
}
return 0;
}
bool getOneLine(void) {
if (inputfile.eof()) {
cout << "END OF FILE" << endl << endl;
return false;
}
else{
getline(inputfile, sentence);
cout << "next sentence is: "<< sentence << endl;
return true;
}
}
I am newbie and I have no one to ask - personally . I tried to edit While cycle and IF's to make sure that I did not make a serious mistake but I have no idea.
I tried it with for example sample.txt and this file was empty.
Always test whether input succeeded after the read attempt! The stream cannot know what you are attempting to do. It can only report whether the attempts were successful so far. So, you'd do something like
if (std::getline(stream, line)) {
// deal with the successful case
}
else {
// deal with the failure case
}
In the failure case you might want to use use eof() to determine whether the failure was due reaching the end of the stream: Having reached the end of file and, thus, std::ios_base:eofbit being set is often not an error but simply the indication that you are done. It may still be an error, e.g., when it is known how many lines are to be read but fewer lines are obtained.
Correct way to use getline() and EOF checking would be like this:
bool getOneLine(void) {
if (getline(inputfile, sentence)) {
cout << "next sentence is: "<< sentence << endl;
return true;
}
if (inputfile.eof())
cout << "EOF reached" << endl;
else
cout << "Some IO error" << endl;
return false;
}
You have one mistake here:
found = what.find(sentence);
You are seeking inside of what for the sentence. If sentence is empty, it will be found.
Change it to
found = sentence.find(what);
You should definitivly learn how to use a debugger. That way you would find such issues pretty fast!

fstream << operate not writing entire output

Everthing goes well until the f << "string" << temp_int << endl; statement
get different results with different openmodes, either doesn't write at all or writes the first two chars of "NumberSaves"
unsigned int temp_int = 0;
fstream f("resources/saveData/Player/savelog.txt");
if (!f)
{
cout << "error accessing savelist" << endl;
}
else
{
string skip;
std::stringstream iss;
string line;
readVarFromFile(f, iss, skip, line, { &temp_int }); //check how many saves currently
temp_int += 1; //increment number of saves by 1
f.seekp(ios_base::beg);
cout << "Write position: " << f.tellp() << endl; //check stream is at beginning
f << "<NumberSaves>" << temp_int << endl; //truncate <NumberSaves> 'x' with <NumberSaves> 'x + 1'
cout << "Write position: " << f.tellp() << endl; //position suggests the entire string has been written, only two characters have been
if (!f)
{
cout << "ERROR";
}
f.seekp(ios_base::end);
f << currentPlayer->getName(); //append players name to end of file
}
desired output is as follows
NumberSaves 2
player
anotherplayer
current output
Nu
player
Use seekp properly like this:
os.seekp(0, std::ios_base::end); // means bring me to 0 from the end of file.
look at the example code in
http://en.cppreference.com/w/cpp/io/basic_ostream/seekp
std::ios_base::end is a direction not an absolute position. It is just an enum value. The value is probably 2 and that is why it brings you to position 2 inside the file.

substr concatenating array elements c++

I am building a function extract the last names from an array and print the name to screen. I have been able to extract the first last name in the array but then the output concatenates the first index's first name with the following index positions last name. Below is my code, thanks for the help!
{
stringstream ss;
string name;
for(int i=0; i < elements; i++)
{
ss << first[i];
ss >> name;
int pos = name.find(",");
cout << pos;
string last = name.substr(0,pos);
cout << "\"" << last << "\"" << endl;
}
cout << endl;
}
It is because the way you are using string streams.
Every time you read a new name from the array, you're adding it to the output buffer. You then read the next word from the buffer so therefore, you never skip the first name . For what it looks like you're doing, you can just eliminate the string stream all together and just stick to the standard input and output (cin/cout). Otherwise, clear the buffer everytime you read in a new string (ss.clear());
for(int i = 0; i < elements.size(); i++){
int pos = elements[i].find(",");
cout << "\"" << elements[i].substr(0,pos) << "\"" << endl;
}
Try the following code:
int main()
{
string name = "asd,kkaa";
int pos = name.find(",");
if(string::npos != pos)
{
string part1 = name.substr(0,pos);
string part2 = name.substr(pos+1);
cout << "\"" << part1 << "\"" << endl;
cout << "\"" << part2 << "\"" << endl;
}
return 0;
}
// output:
// "asd"
// "kkaa"
I think it's OK, so could give us more your input value?

Overwrite a line with ofstream C++

I am doing a little game and I am saving the player details in a txt file.
Example of that txt file:
Eric 13 8 10 10 30 10 10 50 0 0 0 0
William 1 0 10 30 30 10 10 50 0 0 0 0
John 1 0 10 30 30 10 10 50 0 0 0 0
This is what I had in mind: when the player chooses to save the game while playing, the save_game function should check if there is already any saved data. If there is, instead of appending the data to the end of the txt, it should overwrite that specific line.
Here is my current function:
// SAVE GAME
void save_game(Player player)
{
ofstream coutfile (SaveDestiny, ios::app);
if (coutfile.is_open()) // if it opens correctly
{
// Now checking if the name already exists
string imported_name;
ifstream cinfile (SaveDestiny); // opens file that contains the saved games
cinfile >> imported_name; // getting first element of file
bool j = 0; // j = 0 while the strings don't match. j = 1 when the string was found
while (cinfile >> imported_name) // while the end of file is not reached
{
if (player.name.compare(imported_name) == 0) // if the strings are the same, overwrite data
{
j = 1;
coutfile << " \r" << endl;
break;
}
else // if the strings are different, keep reading
{
cinfile >> imported_name;
}
}
// Continuing...
coutfile << player.name << " " << player.level << " " << player.exp << " " << player.max_exp << " "
<< player.hp << " " << player.max_hp << " " << player.mp << " " << player.max_mp << " "
<< player.gold << " " << player.weapon << " " << player.shield << " " << player.heal_spell << " "
<< player.attack_spell << endl;
}
else
{
ofstream coutfile (SaveDestiny, ios::app);
coutfile << "test";
cout << "Unable to open file";
cin.get();
}
draw_rectangle(37,8,72,14,15); // white limits
draw_rectangle(39,9,70,13,9); // blue background
cor(9,15);
gotoxy(50,10);
cout << "GAME SAVED!";
gotoxy(41,12);
cor(9,14);
cout << "Press <Enter> to continue... ";
cin.get();
}
On most modern filesystems files are not "line-based" (or "record-based") they are character-based so you can't "overwrite a line". The old line might be 20 characters long and the new one would be 24 characters, in which case it would overwrite the old line and the first 4 characters of the next line. To make this work you would have to "push" everything after the line later in the file, which isn't possible with C++ (or C) IO facilities.
One option would be to write all lines with a fixed length, say 50 characters, so that overwriting the 3rd line involves replacing characters 100 to 149, even if the line only actually needs 24 characters.
Another option would be to keep the file in memory in a record-based form and write out the entire file every time you change it (or at least write out the new line and all lines that come after it)
Ok I've managed to get around the problem and now it's working brilliantly! :D
First, the function checks if the player name already is on the txt. I created a enable variable j. When j=1, the name exists and the data needs to be overwritten! When j=0, the function will append the data to the txt right away.
Ok, let's say j=1. The function determines the number of lines in txt. It then creates a vector with two vectors inside: the name, and the game variables.
After that, the function deletes the previouscontent of txt file. And writes the content of the vector to the txt, except the data that needs to be overwritten (it will skip writing that part to the txt), because at the end of the function, that new data will be written. :D I hope I made myself clear enough. Sorry if someone doesn't understand what I wrote...
Here is my new save_game function:
// SAVE GAME
void save_game(Player player)
{
ofstream coutfile (SaveDestiny, ios::app);
if (coutfile.is_open()) // if it opens correctly
{
string imported_name;
ifstream cinfile (SaveDestiny); // opens file that contains the saved games
bool j = 0;
// Now checking if the name already exists
while (cinfile >> imported_name) // while the end of file is not reached
{
if (player.name.compare(imported_name) == 0) // if the strings are the same, overwrite data
{
j = 1; // enable overwrite
break;
}
// if the strings are different, keep reading
}
// at this point: j = 0 to append to end. j = 1 to overwrite.
// Overwriting data
if (j == 1)
{
ifstream cinfile (SaveDestiny);
// now determining the size of the vector (number of lines in txt)
int line_numbers = 0;
string line;
while (getline(cinfile, line))
{
line_numbers++;
}
cinfile.close(); // closing
ifstream cinfile2 (SaveDestiny); // reopening to read from the beginning
// now creating the vector with the saves
vector<vector<string>> temp_saves(line_numbers, vector<string>(2));
string name2;
string values;
for (unsigned int x = 0; x < temp_saves.size(); x++)
{
cinfile2 >> name2;
getline(cinfile2, values);
temp_saves[x][0] = name2;
temp_saves[x][1] = values;
}
coutfile.close(); // closing output file
ofstream coutfile2 (SaveDestiny); // reopening in overwrite mode
// delete all saves.txt, copying vector content to txt (except the one we want to overwrite)
for (unsigned int x = 0; x < temp_saves.size(); x++)
{
if ( temp_saves[x][0].compare(player.name) != 0)
{
coutfile2 << temp_saves[x][0] << temp_saves[x][1] << endl;
}
}
coutfile2.close(); // closing output file
}
// Appending new data...
ofstream coutfile3 (SaveDestiny, ios::app); // reopening in append mode
coutfile3 << player.name << " " << player.level << " " << player.exp << " " << player.max_exp << " "
<< player.hp << " " << player.max_hp << " " << player.mp << " " << player.max_mp << " "
<< player.gold << " " << player.weapon << " " << player.shield << " " << player.heal_spell << " "
<< player.attack_spell << endl;
}
else
{
ofstream coutfile (SaveDestiny, ios::app);
cout << "Unable to open file";
cin.get();
}
draw_rectangle(37,8,72,14,15); // white limits
draw_rectangle(39,9,70,13,9); // blue background
cor(9,15);
gotoxy(50,10);
cout << "GAME SAVED!";
gotoxy(41,12);
cor(9,14);
cout << "Press <Enter> to continue... ";
cin.get();
}