I am trying to scan through the content of a .txt file in order to compare it with a user's int input and once found the matching value, line where it is written to be removed.
The file DOES NOT have only numerical values.
Ex of what the file contains:
" hello world 505 "
" hello world 506 " etc.
So far my code is able to make the comparison(the lines do not have the same length) but I do not know how to move the file pointer to the line where said value is found.Any help?
void comparisoniD2 (int a) {
int x[ countLinesOf() ];
ifstream readFile;
readFile.open("ClientList.txt");
string str;
for (int i = 0; i< countLinesOf();i++){
while (getline(readFile, str)) {
reverseStr2(str);
str.erase(3);
reverseStr2(str);
stringstream geek(str);
geek >> x[i];
if( x[i]==a ){
cout<<a<<" is equal to "<<x[i]<<endl;
break;
}
}
}
readFile.close();
}
If you want to do this in the same file it's slightly difficult.
For example you can open the same file twice: for reading strings and for saving strings.
Your cycle would be: read string, save string (if it doesn't contain suitable number).
Another trouble is to cut file to lower size. You can use boost::filesystem or native api.
Related
So I have two simple questions. One is my function okay for reading a text file composed of one number on each line and passing it an array inside main()? And is the text file opening/closing properly or do I not understand the code?
And secondly, I can't seem to fill my array correctly. There's 92 numbers/lines, but I can only seem to get 91 elements. It seems to skip the first number, but I'm not sure why. When I'm debugging I can see "number" reading the the first line, but I don't know where it goes.
The text file is 92 numbers with decimals, with a number in each line like this..and the first number is in the first line, no space above and no vertical space between the numbers.
31.11
25.22
...
int getTempData(double temperatures[]) {
ifstream input("pgm6.txt");
if (!input)
return 1; // closes input file
string number;
while (input >> number)
for (int i = 0; i < 91; i++)
{
input >> temperatures[i];
}
}
and inside main()
const int ARRAY_SIZE = 91;
double temperatures[ARRAY_SIZE];
getTempData(temperatures);
Edit: Thanks so much for the help everyone. I learned my lesson in not using code I don't quite understand from here: https://www.reddit.com/r/learnprogramming/comments/2wwv6i/c_creating_writing_to_and_displaying_text_files/
#include <fstream> // Instead of <iostream>
#include <string>
using namespace std; // Nothing too much wrong with this...
int main() {
ifstream input("input.txt"); // Open the file "input.txt" for reading
(if = input file)
if ( !input ) // Did the file open correctly?
return 1;
ifstream output("output.txt"); // Open the file "output.txt" for writing
(of = output file)
if ( !output ) // Did the file open correctly?
return 1; // C++ automatically closes the input file!
string word;
**while ( input >> word )** // Read a word while the file isn't at its
end
output << word << '\n'; // Write the word on its own line
// C++ automatically closes the output file
// C++ automatically closes the input file
}
What you are trying to achieve seems to boil down to this:
#include <fstream>
int getTempData(double temperatures[]) {
std::ifstream input("pgm6.txt");
int i;
for (i = 0; i < 92 && input >> temperatures[i]; i++) {
// deliberate empty line
}
// input will close file on exiting function
return i; // returns number of elements found
}
int main() {
const int ARRAY_SIZE = 92;
double temperatures[ARRAY_SIZE];
getTempData(temperatures);
}
while (input >> number)
This reads the first number and throws it away. Simply remove this line of code.
Also, you should probably add error checking to input >> temperatures[i];. And your function needs to return something if all is well -- currently there is no return statement at the end. Also, your loop only collects 91 elements.
unformatted_grades.txt:
formatted_grades.txt:
I am working on an assignment where my professor wants me to open and read a .txt file with different strings inside of it. We are supposed to format the content of the file.
Ex:
The read_grade_file method has a parameter int number_of_students
The first line of the file is "number_of_students 9"
I have opened and read the file and pushed each individual line into a string vector.
How do I get the number 9 in the first line by itself so I can make the number_of_students parameter equal to it???
Please help.
(We are allowed to skip over or delete any irrelevant data from the vector).
My code:
void Read_Grade_File(string names[MAX_CLASS_SIZE][2], int scores[MAX_CLASS_SIZE][MAX_NUMBER_OF_ASSIGNMENTS], int *number_of_students, int *number_of_assignments, const string input_filename) {
string currline; // temporarily holds the content of each line read from the file
ifstream inFile; // filestream
vector<string> content; // vector containing each string from the file
inFile.open(input_filename); //open the file.
if (inFile.is_open()){
// reads file and pushes the content into a vector
while(!inFile.eof()){
getline(inFile, currline);
if(currline.size() > 0){
content.push_back(currline);
}
}
}
// prints the content stored in the vector
for (int i = 0; i < content.size(); i++){
cout << content[i] << endl;
}
}
Rather than reading the entire line at once, it may make more sense to read the various values on the line as you go. For example, if you know the format of the file, then you can read the first variable's name followed by reading the value of the variable like this:
std::string variableName;
int variableValue;
inFile >> variableName;
inFile >> variableValue;
So you could get the variables whose names you know, find their values, and then loop through the rest of the file reading in that many records.
I am unable to read '.dat' file. I have tired all the possible ways and tired googling it but I could not find the solution. All it gives me is a null value for integer and a junk value for a string variable or char. This what I have written
ifstream file;
file.open("data1.dat"); // I have also tried this way too like file.open("data1.dat", ios::binary, ios::in);
int data=0;
file >> data;
cout << data << endl;
system("pause");
return 0;
I am using visual studio to compile this code. I am pretty sure that the pointer is entering into the data file but I don't know for what reason the data is not being read.
The .dat file consists of integer number per line ranging from 0, so I just need to read the file and get number from each line and should find the sum of all numbers in the file. The file contains number like
5,
468,
3200,
32, etc.,. Each number is in a new line. The file can contain any number of records. this how .dat file looks when opened using a notepad editor
Your code "works" on my system.
The following compiles (without "using namespace std;")
I changed the file name for my convenience.
I created the 't391.dat' file in the same working directory of the code, and put in 10 lines, with 1 value per line, 1..9,0.
#include <fstream>
#include <iostream>
int t391a(void)
{
std::ifstream file;
file.open("t391.dat");
int data=0;
file >> data;
std::cout << data << std::endl; // echo of input / proof it works
//system("pause");
file.close();
return 0;
}
This code outputs the first value (which is all it attempts to do), so it is working!
The echo of input is good idea.
As an experiment, I temporarily renamed the 't391.dat' file to something else. The code ran to completion and printed a single 0, which is not the first value in the file. Perhaps this suggests your file is not being found, I won't guess. To confirm, I restored the file, and the above 'works' again.
Missing items in your code:
error check - file.open()
a loop to read to end of file
error check - formatted extract (i.e. read from stream) of data item
file.close - possibly not needed
If you are still working this issue, I have a minimally extended version of your code that addresses these issues. Let me know.
class ValueGet {
public:
int data;
ValueGet() {
data = 0;
}
};
int main()
{
ValueGet vg;
ifstream file;
file.open("data1.dat", fstream::binary | fstream::out); // Opens a file in binary mode for input operations i.e., getting data from file.
if (!file)
cout << "File Not Found." << endl;
else {
file.seekg(0); // To make sure that the data is read from the starting position of the file.
while (file.read((char *)&vg, sizeof(vg))) // Iterates through the file till the pointer reads the last line of the file.
cout<<vg.data<<endl;
}
//system("pause");
return 0;
}
output of the data in the file
Here is one way which I just found
#include <bits/stdc++.h>
using namespace std;
int main(){
unsigned int a;
unsigned char c;
ifstream file;
file.open("ou.bin", ios::binary);
if(!file.is_open()){
cout<<"error";
return 0;
}
for(int i=0; i<8; i++){
file>>c;
a = c;
a = a<<8;
file>>c;
a = a+ c;
cout<<a<<endl;
}
file.close();
return 0;
}
This for storing two bytes in a number you can store as many bytes in a number or even one.
Hope this helps.
You will not be able to read .dat files and understand them in your context-- they are general formats used for storing data. Unless you know the contents of it or how they are specified, you will always get junk.
I wrote a code in C++ that writes a .txt file.
Then I want to open the code again and give some information, so I can get a new text depending on what I gave as an input.
For example I want to give the name of a month, and print in another .txt file all the lines that came after the word "November".
I found some solutions, but none of them worked for me!
One solution that I found on stack overflow is the following:
void Keyword(ifstream & stream, string token) {
string line;
while (getline(stream, line)) {
if (line.find(token) != string::npos) {
cout << line << endl;
}
}
cout << token << " not found" << endl;
}
I can't print the next lines with the code above.
Any suggestion would be helpful!
Thanks!
If you want to perform operations on files such as 'Read' and/or 'Write',you might want to search on the net(or if you have a C++ book) on topics such as "File I/O operations using C++". Anyways moving on, C++ has 2 basic classes to handle files which are ifstream and ofstream. And to use them you have to include ethier the header fstream(i.e #include<fstream>) or include them separately as #include<ifstream> and #include<ofstream>. ifstream is basically used for all input operations such as reading files etc. Similarly ofstream is used for all output operations such as writing data to files.
You can open a file and write data to it by doing the following,
ofstream myFile("filename");// Create an instance of ofstream and open file for writing data
and to write data to the file use the << operator like below,
myFile<<data;
Similarly, You can open a file and read data as follows,
ifstream myFile("filename");//Create an instance of ifstream and open file to read data
and to read data from the file use the >> operator as shown below,
myFile>>data;
You can also open a file using the method void open(const char *filename, ios::openmode mode); as shown below,
//Writing only
ofstream outFile;
outFile.open("filename.txt",ios::out);
//Reading only
ifstream inFile;
inFile.open("filename.txt",ios::in);
//For reading and writing
fstream file;
file.open("filename.txt",ios::in|ios::out);
//For closing File
outFile.close();
//or
inFile.close();
//or
file.close();
Note the open() method takes various flags such as ios::in for reading mode, ios::out for writing mode, ios::app for adding data to the end etc.
All of these can also combined by using the bit OR operator | as shown below,
outFile.open("filename.txt",ios::out|ios::app);
There is a lot more in IO. I just covered the things required to start.
Here is the solution to your problem. Try to understand it.
#include<iostream>
#include<fstream>
#include<cstring>
using namespace std;
int main()
{
ofstream outFile;
ifstream inFile;
char fileName[10],data[50];
int noLines;
cout<<"Enter Month:"<<endl;
cin>>fileName;
cout<<"Enter Number of lines you want to enter:"<<endl;
cin>>noLines;
outFile.open(fileName,ios::out);
cout<<fileName<<"(Enter Data):";
for(int i=0;i<=noLines;i++)
{
cin.getline(data,50);
outFile<<data<<endl;
}
outFile.close();
cout<<"Openening "<<fileName<<" :"<<endl;
inFile.open(fileName,ios::in);
for(int i=0 ;i<=noLines ;i++)
{
inFile.getline(data,50);
cout<<data<<endl;
}
inFile.close();
return 0;
}
OP has found most of the solution already:
string line;
while (getline(stream, line)) {
if (line.find(token) != string::npos) {
cout << line << endl;
}
}
cout << token << " not found" << endl;
But this only prints the lines with the keyword. And always prints the "not found" message. Ooops.
Instead I pitch:
string line;
bool found = false;
while (!found && getline(stream, line))
{ // search for keyword
if (line.find(token) != string::npos)
{
found = true; // found keyword. Stop looking
}
}
if (found)
{ // print out all remaining lines in the file
while (getline(stream, line))
{
cout << line << endl;
}
}
else
{
cout << token << " not found" << endl;
}
The above splits the finding of the token and the printing of the remaining file into two stages for readability. It can be compressed into one loop, but two things make this a sucker bet:
this program will be IO bound. It will spend the vast majority of its time reading the file, so little tweaks that do not address getting the file into memory are wasted time.
combining the loops would require the addition of logic to the loop that would, over along run, dwarf the minuscule cost of switching loops.
Try this:
http://www.cplusplus.com/doc/tutorial/files/
and this:
http://www.cplusplus.com/forum/beginner/14975/
It's about reading and writing files in c++ and about searching in files.
I have a text file that contains several words, all separated by spaces. I'm trying to read the file and then put it into an array, so that each word is a separate value in said array. I'm using this code, but when I run my program, it doesn't display anything (like it should.)
ifstream file ("words.txt");
if(file.is_open())
{
string wordArray[100];
for(int i = 0; i < 100; ++i)
{
file >> wordArray[i];
cout << i;
}
cout << "File is open.";
}
Nothing displays at all. I'm doing this in a void function, which isn't being passed anything currently, but I don't think that has anything to do with it. The code should at least display "File is open" or any number from 1 to 100, but I don't get anything. I don't understand why this isn't working, as I'm including iostream, string, fstream, iomanip, and sstream. If there's something simple I'm overlooking, please let me know.
Well, your program probably isn't passing the statement in the if condition.
Try adding this to test your file is opening correctly:
if(file){
// do all the file inputs
}
else{
std::cerr << "could not open file words.txt" << std::endl;
}