I need to create a program that reads a file, pushes the content into a stack, then writes that content in reverse to another file. I don't understand why my file isn't being found or outputting. Here is my code:
#include "stdafx.h"
#include <iostream>
#include <stack>
#include <fstream>
#include <string>
int main() {
std::stack<char>charStack;
std::fstream file;
std::fstream revFile;
std::string fileName;
std::cout << "Enter the name of the file you want to open." << std::endl;
std::cin >> fileName;
file.open(fileName);
std::cout << "Adding input from file to stack." << std::endl;
char ch;
file >> std::noskipws;
while (file >> ch) {
std::cout << ch;
charStack.push(ch);
}
file.close();
revFile.open("newFile.txt");
std::cout << std::endl;
std::cout << "Reversing stack and writing to file." << std::endl;
while (!charStack.empty()) {
char i = charStack.top();
revFile << i;
charStack.pop();
}
revFile.close();
revFile.open("newFile.txt");
std::cout << "Here is the original file reversed." << std::endl;
std::string line;
if (revFile.is_open()) {
while (std::getline(revFile, line)) {
std::cout << line;
}
revFile.close();
}
else std::cout << "Unable to open file" << std::endl;
revFile.close();
return 0;
}
I'm unsure if I need to add an empty .txt file to write to or if this should generate one for me. Any help would be appreciated.
You need to change the file opening statements to be:
revFile.open("newFile.txt",ios::out); //for output
and
revFile.open("newFile.txt",ios::in); //for input
other than that, you just need to correct this line to get a correct printing of the file contents after reversing.
std::cout << line;
Make it:
std::cout << line << "\n";
Related
I've written a readFile function for a project I'm working on. I call it once, load in a file and read in it's contents - works fine
However, when I try to load it a second time, attempting to change the file name - it loads it in, saves it to a static string 'path' that I access in a different function - but then the function is not printing the data
The question is, how do I change the file name, and read it in successfully on the second iteration? The part that has me stumped is that it works once, but not twice
Ive attempted to use cin.ignore(); cin.clear(); cin.sync() on the second iteration of fileName function - but none of them allow a separate file to be read successfully.
Minimum Reproducible Example:
#include <iostream>
#include <fstream>
#include <string>
#include <stdlib.h>
#include <vector>
#include <sstream>
#include <iomanip>
#include <iostream>
using namespace std;
static string path;
string opt;
void readFile();
int fileName();
void menu() { // put in while loop - while True
cout << "----------------------" << endl;
cout << "R(ead) -" << "Read File" << endl;
cout << "F(ile) -" << "Set Filename" << endl;
cout << "\nPlease select from the above options" << endl;
cin >> opt;
cout << "\nInput entered: " << opt << endl;
if (opt == "R") {
readFile();
}
if (opt == "F") {
fileName();
}
}
void readFile() { // doing this twice
ifstream readFile;
readFile.open(path);
if (!readFile.is_open()) {
cout << "Could not read file" << endl;
}
string str;
int i = 0;
while (getline(readFile, str))
{
if (str[0] != '/')
{
cout << "DEBUG: Line is - " << str << endl;
}
}
readFile.clear();
readFile.close();
menu();
}
int fileName() {
cout << "File path: ";
if (path != "") {
cin.ignore();
cin.clear();
cin.sync();
}
getline(cin, path);
ifstream file(path.c_str());
if (!file) {
cout << "Error while opening the file" << endl;
return 1;
}
cout << "(File loaded)" << endl;
cout << "Path contains: " << path << endl;
file.clear();
file.close();
menu();
}
int main()
{
fileName();
}
Sample text, saved as txt file and read in using path:
Data1.txt
// standard test file
123,Frodo inc,2006, lyons,"1,021,000.16",0.0,
U2123,Sam Inc,2006, lyons,"21,600.00",13.10,123
A721,Merry Inc,2604, Kingston,"21,600.10",103.00,
U2122,Pippin Inc,2612, reid,"21,600.00",0
U1123,Huckelberry corp,2612, Turner,"21,600.00",13.10,
Data2.txt
7101003,Mike,23 boinig road,2615,48000,12000,0
7201003,Jane Philips,29 boinig cresent,2616,47000,12000,0
7301003,Philip Jane,23 bong road,2615,49000,000,0
7401004,Peta,23 bong bong road,2615,148000,19000,0
7101205,Abdulla,23 Station st,2615,80000,21000,0
The problem comes from reading in one, and trying to read in the other after the first has been executed.
Enter Filename
Hit Readfile
Return to menu, hit Set Filename
Change to Data2.txt
Readfile again. Not working
My tutor told me "That's not how functions work in c++" but didn't elaborate further, and is unavailable for contact.
In general, do not use global variables. The path variable should be passed as a parameter, not kept as a global variable altered between function calls, as this leads to many side effects and is the source of countless bugs. See the following refactoring:
void menu() { // put in while loop - while True
while(true)
{
//Keep this as a local variable!
std::string opt;
std::string filename;
cout << "----------------------\n";
cout << "R(ead) -" << "Read File\n";
cout << "F(ile) -" << "Set Filename\n";
cout << "\nPlease select from the above options\n";
cin >> opt;
cout << "\nInput entered: " << opt << '\n';
if (opt == "R") {
readFile(filename);
}
if (opt == "F") {
filename = getFileName();
}
}
}
void readFile(const std::string & filename) {
ifstream readFile;
readFile.open(filename);
if (!readFile.is_open()) {
cout << "Could not read file " << filename << '\n';
}
string str;
int i = 0;
while (getline(readFile, str))
{
if (str[0] != '/')
{
cout << "DEBUG: Line is - " << str << '\n';
}
}
readFile.close();
//just return to get back to menu
return;
}
std::string getFileName() {
cout << "File path: ";
std::string path;
getline(cin, path);
ifstream file(path.c_str());
if (!file) {
cout << "Error while opening the file" << '\n';
//Instead of returning an error code use an exception preferably
}
cout << "(File loaded)" << '\n';
cout << "Path contains: " << path << '\n';
file.close();
return path;
}
Other notes:
Ideally, do input in output in just one function, not all three as it gets confusing exactly what each function is responsible for.
If you want something to hold a file and print the contents, you can use an class.
The file is checked if it is openable twice, not really any reason to do this just delegate that responsibility to one function.
One of the best things about C++ is RAII and deterministic lifecycles for objects and primitives - use it!! Do not give everything a long life with global variables - use smart parameters and return values instead.
trying to format with c++ getline function. The output puts everything at the first record number forename instead of where it should go.
Code:
#include <fstream>
#include <string>
#include <iostream>
using namespace std;
int main()
{
const int RANGE = 12;
string tab[RANGE];
int i = 0, j = 0;
ifstream reader("records.txt");
if (!reader)
{
cout << "Error opening input file" << endl;
return -1;
}
while (!reader.eof())
{
if ( ( i + 1) % 4 == 0)
getline( reader, tab[i++], '\n');
else
getline( reader, tab[i++], '\t');
}
reader.close();
i = 0;
while (i < RANGE)
{
cout << endl << "Record Number: " << ++j << endl;
cout << "Forename: " << tab[i++] << endl;
cout << "Surname: " << tab[i++] << endl;
cout << "Department: " << tab[i++] << endl;
cout << "Telephone: " << tab[i++] << endl;
}
return 0;
}
Contents of TXT file:
John Smith Sales 555-1234
Mary Jones Wages 555-9876
Paul Harris Accts 555-4321
Please run the code for yourself to understand what happens and put the txt file in the same folder as your code.
Hope someone can help me thanks.
See Why is iostream::eof inside a loop condition (i.e. while (!stream.eof())) considered wrong?.
Also, your final while loop should only output the strings that were actually read into the array, not the full array, if the file has less than 12 strings. But unless you can guarantee that your file never exceeds 12 strings, you should use std::vector instead of a fixed array.
Also, instead of alternating the getline() delimiter in a single loop, I would just use an outer loop to read whole lines only, and then separately read tab-delimited values from each line. And then store the values in an array/vector of struct instead of individually.
Try something more like this:
#include <fstream>
#include <sstream>
#include <string>
#include <iostream>
#include <vector>
using namespace std;
struct Person
{
string foreName;
string surName;
string department;
string phoneNumber;
};
int main()
{
ifstream reader("records.txt");
if (!reader)
{
cout << "Error opening input file" << endl;
return -1;
}
vector<Person> people;
string line;
while (getline(reader, line))
{
istringstream iss(line);
Person p;
getline(iss, p.foreName, '\t');
getline(iss, p.surName, '\t');
getline(iss, p.department, '\t');
getline(iss, p.phoneNumber, '\t');
people.push_back(p);
}
reader.close();
int j = 0;
for (Person &p : people)
{
cout << endl << "Record Number: " << ++j << endl;
cout << "Forename: " << p.foreName << endl;
cout << "Surname: " << p.surName << endl;
cout << "Department: " << p.department << endl;
cout << "Telephone: " << p.phoneNumber << endl;
}
return 0;
}
There are easier ways to separate words in an istream, namely C++ sring stream tools:
#include <fstream>
#include <iostream>
#include <sstream> //<-- string stream library
using namespace std; //<-- should not be used, use scope std::
int main() {
const int RANGE = 12;
string tab[RANGE];
string temp; //<--to store each field temporarily
int i = 0, j = 0;
ifstream reader("records.txt");
if (!reader) {
cout << "Error opening input file" << endl;
return -1;
}
while (getline(reader, temp)) { //<-- read one full line
stringstream ss(temp); // <-- input to a string stream
while(ss >> tab[i]){ // <-- passing strings to the string array one by one
i++;
}
}
reader.close();
i = 0;
while (i < RANGE) {
cout << endl << "Record Number: " << ++j << endl;
cout << "Forename: " << tab[i++] << endl;
cout << "Surname: " << tab[i++] << endl;
cout << "Department: " << tab[i++] << endl;
cout << "Telephone: " << tab[i++] << endl;
}
return 0;
}
The idea here was to mess as little as possible with your code, one thing I would advise is to use std::vector instead of normal fixed size arrays. Also, as it was said and linked, eof is very unreliable.
The source of your problem, I think, is explained in Why is iostream::eof inside a loop condition (i.e. `while (!stream.eof())`) considered wrong?.
You are reading into tab[12], tab[13], tab[13], and tab[14] due to that error. Of course, that leads to undefined behavior.
Change the loop to:
// Read the contents of the file line by line
std::string line;
while (getline( reader, line))
{
// Process each line's contents.
std::istringstream str(line);
getline(str, tab[i++], '\t');
getline(str, tab[i++], '\t');
getline(str, tab[i++], '\t');
getline(str, tab[i++], '\n');
}
Make sure to add
#include <sstream>
To be doubly sure that you are not using the array using out of bounds indices, add a check.
while ( i+4 < RANGE && getline( reader, line))
{
...
}
First, while (!reader.eof()) is not doing the right thing.
The immediate problem you see is caused by the fact that your file does not contain '\t', hence already the very first getline reads all the contents of the file into tab[0]. (At least thats what I got after 1-to-1 copying your file contents)
Your code is rather difficult, because you declare variables long before you use them and later reuse them. You have a fixed size array, but when there are more lines in the file your code will just crash. Also reading everything into a plain array of strings is making things complicated. Accessing forename or other fields requires you to compute the offset into the array. Better use a data structure:
struct file_entry {
std::string first_name;
std::string last_name;
std::string departure;
std::string phone;
};
Then you can define an input operator:
std::istream& operator>>(std::istream& in,file_entry& fe) {
return in >> fe.first_name >> fe.last_name >> fe.departure >> fe.phone;
};
And use a std::vector to store as many entries as there are in the file:
int main() {
std::string contents{"John Smith Sales 555-1234\n"
"Mary Jones Wages 555-9876\n"
"Paul Harris Accts 555-4321\n"};
std::stringstream reader{contents};
std::vector<file_entry> data;
std::string line;
while (std::getline(reader,line)) {
file_entry fe;
std::stringstream{line} >> fe;
data.push_back(fe);
}
for (const auto& fe : data) {
std::cout << "Forename: " << fe.first_name << '\n';
std::cout << "Surname: " << fe.last_name << '\n';
std::cout << "Department: " << fe.departure << '\n';
std::cout << "Telephone: " << fe.phone << '\n';
}
}
live example
PS you do not need to call close on the file, this is already done in its destructor. Not calling it explicitly has the benefit that the same code that works for a file stream also works for a stringstream.
I try to find same lines between two text files.
while (getline (texta,str1)){
while (getline (textb,str2)){
cout<<str1<<str2<<endl;
}}
First while working very well but second one just read first part line of text and then quit. I've tried different textes but doesnt work.
If you want to look all code:
void similars(string text1,string text2){
string str1,str2;
ifstream texta(text1.c_str());
ifstream textb(text2.c_str());
if(texta.is_open() && textb.is_open()){
while (getline (texta,str1)){
while (getline (textb,str2){
cout<<str1<<str2<<endl;
}
}
}
else cout << "Unable to open file";
}
don't mix things those shouldn't do
consider this example:
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
void similars(string text1, string text2)
{
string str1, str2;
ifstream texta(text1.c_str(), ios::in);
ifstream textb(text2.c_str(), ios::in);
cout << "text1: " << endl << endl;
while(!texta.eof())
{
getline (texta, str1);
cout << str1 << endl;
}
cout << endl << endl;
texta.close(); // closing safely the file
cout << "text2: " << endl << endl;
while(!textb.eof())
{
getline (textb, str2, '\n');
cout << str2 << endl;
}
textb.close();
cout << endl;
}
int main()
{
system("color 1f");
string sText1 = "data1.txt";
string sText2 = "data2.txt";
similars(sText1, sText2);
system("pause");
return 0;
}
just create two text files with notepad or any text editor, rename them to "text1.txt", "text2.txt" and put some text in them and save and close. then run the program.
This question already has an answer here:
boost::iostream::copy(), inputstream and outstream output explanantion
(1 answer)
Closed 7 years ago.
I have a txt file: gcc-4.7.2.txt : with the data written: Hello This is a test file. Thanks :compressed as gcc-4.7.2.tar.bz2
Now, I run the following code:
#include <sstream>
#include <fstream>
#include <iostream>
#include <boost/iostreams/filtering_streambuf.hpp>
#include <boost/iostreams/copy.hpp>
#include <boost/iostreams/filter/bzip2.hpp>
#include <boost/filesystem.hpp>
int main()
{
using namespace std;
using namespace boost::iostreams;
char filename[] = "gcc-4.7.2.tar.bz2";
if (!boost::filesystem::exists(filename))
{
cout << "Can't find " << filename << ". Expect errors to follow! " << endl;
}
ifstream file(filename, ios_base::in | ios_base::binary);
filtering_streambuf<input> in;
filtering_streambuf<output> out;
in.push(bzip2_decompressor());
in.push(file);
try
{
//cout << "in_file:" << in << endl;
boost::iostreams::copy(in, cout);
//boost::iostreams::copy(in, out);
//cout << cout << endl;
//boost::iostreams::copy(in, compressed_string);
//cout << "Copied" << compressed_string << " " << in.str() << endl;
}
catch (const bzip2_error& exception)
{
cout << "catchblock" << endl;
cout << exception.what() << endl;
int error = exception.error();
if (error == bzip2::data_error)
{
cout << "compressed data stream is corrupted";
}
else if (error == bzip2::data_error_magic)
{
cout << "compressed data stream does not begin with the 'magic' sequence 'B' 'Z' 'h'";
}
else if (error == bzip2::config_error)
{
cout << "libbzip2 has been improperly configured for the current platform";
}
else
{
cout << "Error: " << error;
}
cout << endl;
}
}
While running it the output is:
dev4#sun-desktop:~/readerwriter$ ./test1
gcc-4.7.2.txt0000644000175100001440000000004312547435102011603 0ustar dev4usersHello
This is a test file.
Thanks
What are the characters before Hello ? why is it printing the file name?
How to get rid of those extra values.
and only print the content of the file:
Hello
This is a test file.
Thanks
You cannot.
These are not "extra values".
If you don't want a tar archive, just do not use tar.
Instead, use bzip2 to compress the single file
If the input is a tar archive, extract with tar.
Boost does not support tar archives
This currently reads a .txt file and sorts the contents. I'm trying to get it to write those sorted contents of the vector to a file. Currently it only writes one line, how can I can get it to put all lines in the new file? Thank you so much. -Kaiya
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <fstream>
using namespace std;
inline void keep_window_open() {char ch; cin>>ch;}
int main()
{
string line;
ifstream myfile("weblog.txt");
vector<string> fileLines;
//stack overflow example
if (!myfile) //test the file
{
cout << "Unable to open the file" << endl;
return 0;
}
while (getline(myfile, line))
{
fileLines.push_back(line);
//cout << line << '\n';
}
sort(fileLines.begin(), fileLines.end()); //sorting string vector
for (string &s : fileLines)
{
cout << s << " ";
ofstream newfile ("newfile.txt");
newfile << s << " ";
};
return 0;
}
ofstream newfile ("newfile.txt");
for (string &s : fileLines)
{
cout << s << " ";
newfile << s << " ";
};
Creating newfile for every loop iteration overwrites the content of the file, by default.
Either open newfile before the last loop, or open it in append mode within the loop.
It's because you are creating a new file in each iteration of your loop!
ofstream newfile("newfile.txt");
should be written before the loop.
ofstream newfile ("newfile.txt");
for (string &s : fileLines)
{
cout << s << " ";
newfile << s << " ";
};
ofstream newfile ("newfile.txt");
copy(fileLines.begin(), fileLines.end(), ostream_iterator<string>(newfile, " ") );
Here is my complete code that worked, thanks Xiaotian Pei for your help.
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <fstream>
using namespace std;
inline void keep_window_open() {char ch; cin>>ch;}
int main()
{
string line;
ifstream myfile("weblog.txt");
vector<string> fileLines;
if (!myfile) //test the file
{
cout << "Unable to open the file" << endl;
return 0;
}
while (getline(myfile, line))
{
fileLines.push_back(line);
}
sort(fileLines.begin(), fileLines.end()); //sorting string vector
ofstream newfile ("newfile.txt"); //write to new file
for (string &s : fileLines)
{
cout << s << " ";
newfile << s << " ";
}
return 0;
}