I need to know if you can easily get the number of data entries in another file and save that number in the original file. Need a program that will process the other file no matter how many entries are in it. Hope that makes any sense.
Your question is very poorly worded but I think you are looking for getline. This function can parse an input file based on the newline character (default behaviour) or based on a user provided delimiter:
int entryCount = 0;
std::string currentLine;
std::ifstream inFile( "in.txt" );
std::ofstream outFile;
if (inFile) // short for inFile.good())
{
while (std::getline( inFile, currentLine))
{
++entryCount;
// Do your processing
}
inFile.close();
outFile.open( "out.txt" );
outFile << "End of file. " << entryCount << " entries read." << std::endl;
outFile.close();
}
else
std::cout << "oops... error opening inFile" << std::endl;
Related
I want to append text to the file "filename.txt" but the text won't append. I have even set the attribute ios_base::app but it does not work(I have tried deleting the file and starting the program again so that the part where the attribute is added will be run;
ifstream MyReadFile("filename.txt");
ifstream f("filename.txt");
bool exits_and_can_be_opened = f.good();
if (exits_and_can_be_opened) {
cout << "This file already exists";
}
else {
MyWriteFile.open("filename.txt", ios_base::app);
MyWriteFile << "Files can be tricky, but it is fun enough!";
MyWriteFile.close();
}
while (getline(MyReadFile, myText)) {
// Output the text from the file
cout << myText << "\n";
}
MyWriteFile << "This thing was appended";
cout << "This was the final change";
You could open the file for reading and writing, and then use positioning functions to move around in the file or to switch from reading to writing
fstream MyFile("filename.txt");
while (getline(MyFile, myText)) {
// Output the text from the file
cout << myText << "\n";
}
MyFile.clear(); // clear any error
MyFile.seekg(0, ios_base::end); // move to the end of the file
MyFile << "This thing was appended";
The other (maybe simpler) way is to close and reopen the file every time you want to switch from reading to writing. Don't have the same file opened twice simultaneously.
I'm trying to read multiple files in a folder so I can parse through their data.
I first try to fill the list using a text document with all the file names in it, then based on that vector of string, continuously call ifstream so I can read every file and process the word data.
The problem I'm running into is that ifstream is failing to open all of the files, except one in the middle of the list?
Heres the output, its failing to read the dbfiles but they all have the right names?
These files aren't more than 8GB a piece so it should be able to handle it but it's not?
maybe theres a problem with the file paths?
std::ifstream dbfiles(argv[1]);
if (!dbfiles)
{
std::cerr << "Failed to open database " << argv[1] << " for reading." << std::endl;
}
std::string word;
std::vector<std::string> dbfile_names;
std::string file_name;
while (getline(dbfiles, file_name))
{ //reading in the file names
dbfile_names.push_back(file_name);
}//populate list of dbs
dbfiles.close();
for (unsigned int j = 0; j < dbfile_names.size(); j++)
{ //for every single file
std::ifstream dbfile(dbfile_names[j].c_str());
if (!dbfile)
{
std::cout << "Failed to open database file" << dbfile_names[j] << " for reading. READ FAILURE" << std::endl;
}else{
std::cout << "currently reading " << dbfile_names[j] << std::endl;
}
while (dbfile >> word)
{
//do stuff with the segments of data
//here I gather the data word by word and process it
}
dbfile.close();
}
I went into my debugger and found that due to getline, all the file names had a /r at the back of them.
The post over here Getting std :: ifstream to handle LF, CR, and CRLF?, helped describe the problem and how to easily fix it.
My files are now reading accordingly
Note: I am using the C++11 standard, so I don't see why this isn't working with or without c_str() appended.
I have the following code:
// open streams
ifstream in(input);
ofstream out(output);
// get which file to open
in.ignore(INT_MAX, ':'); // we don't need the beginning part
in.ignore(); // remove trailing whitespace
string fileLocation;
getline(in, fileLocation);
out << "Loading: " << fileLocation << endl;
cout << "Loading: " << fileLocation << endl;
// now that we know where the file is, load it:
ifstream file(fileLocation);
which reads from a file that looks vaguely like this
File: file.txt
(Subcommands below)
I know that I am pulling the correct filename because of the terminal output.
Anyway, I noticed that the stream wasn't opening properly, so I added this conditional to check:
if ( !file )
{
cout << "File wasn't loaded properly." << endl;
}
And sure enough, I see that message when running the program.
My question is this: how come, when I hard-code the file location, e.g. ifstream file("file.txt") it opens up no problem? How do I get this working properly?
Edit: changed my question to be more accurate of the situation
I'm trying to open up a text file (create it if it doesnt exist,open it if it doesnt). It is the same input file as output.
ofstream oFile("goalsFile.txt");
fstream iFile("goalsFile.txt");
string goalsText;
string tempBuffer;
//int fileLength = 0;
bool empty = false;
if (oFile.is_open())
{
if (iFile.is_open())
{
iFile >> tempBuffer;
iFile.seekg(0, iFile.end);
size_t fileLength = iFile.tellg();
iFile.seekg(0, iFile.beg);
if (fileLength == 0)
{
cout << "Set a new goal\n" << "Goal Name:"; //if I end debugging her the file ends up being empty
getline(cin, goalSet);
oFile << goalSet;
oFile << ";";
cout << endl;
cout << "Goal Cost:";
getline(cin, tempBuffer);
goalCost = stoi(tempBuffer);
oFile << goalCost;
cout << endl;
}
}
}
Couple of issues. For one, if the file exist and has text within it, it still goes into the if loop that would normally ask me to set a new goal. I can't seem to figure out what's happening here.
The problem is simply that you are using buffered IO streams. Despite the fact that they reference the same file underneath, they have completely separate buffers.
// open the file for writing and erase existing contents.
std::ostream out(filename);
// open the now empty file for reading.
std::istream in(filename);
// write to out's buffer
out << "hello";
At this point, "hello" may not have been written to disk, the only guarantee is that it's in the output buffer of out. To force it to be written to disk you could use
out << std::endl; // new line + flush
out << std::flush; // just a flush
that means that we've committed our output to disk, but the input buffer is still untouched at this point, and so the file still appears to be empty.
In order for your input file to see what you've written to the output file, you'd need to use sync.
#include <iostream>
#include <fstream>
#include <string>
static const char* filename = "testfile.txt";
int main()
{
std::string hello;
{
std::ofstream out(filename);
std::ifstream in(filename);
out << "hello\n";
in >> hello;
std::cout << "unsync'd read got '" << hello << "'\n";
}
{
std::ofstream out(filename);
std::ifstream in(filename);
out << "hello\n";
out << std::flush;
in.sync();
in >> hello;
std::cout << "sync'd read got '" << hello << "'\n";
}
}
The next problem you'll run into trying to do this with buffered streams is the need to clear() the eof bit on the input stream every time more data is written to the file...
Try Boost::FileSystem::is_empty which test if your file is empty. I read somewhere that using fstream's is not a good way to test empty files.
I am trying to create a program in C++ using Microsoft Visual Studio 2013. The main purpose of this program is to read three different files(headlines1,headlines2, and headlines3) and put them all together to form a single file and creating a sentence within that output file. I have figured out a function that I could use, but this function only reads and prints the 3 files out onto the console window. When I try to change the cout statement into an outfile, my outfile that I created is blank... I don't know what to do or how to structure the code.
#include<fstream>
#include<iostream>
#include<cstdlib>
using namespace std;
void readingFile(string[], ifstream &); //Funtion Prototype
int main()
{
string header1[50], header2[50], header3[50]; //Declaring array with 50 elements
int size1, size2, size3;
ifstream Fin, Fin2, Fin3;
ofstream Fout;
Fin.open("Headlines1.txt"); //Reading from these 3 files.
Fin2.open("Headlines2.txt");
Fin3.open("Headlines3.txt");
if (!Fin || !Fin2 || !Fin3) //Checking for unsuccessful open
{
cout << "Input file opening failed.\n";
cin.ignore();
return 1;
}
Fout.open("testingHeadlines.txt"); //Used for unsuccessful opening output
if (!Fout)
{
cout << "Output file opening failed.\n";
cin.ignore();
return 2;
}
cout << "Building.... Editing....\n" << endl;
cin.ignore();
cout << "Headlines file 1 below:\n" << endl;
readingFile(header1, Fin); //Function call
cout << endl << endl;
cout << "Headlines file 2 below:\n" << endl;
readingFile(header2, Fin2); //Function call
cout << endl << endl;
cout << "Headlines file 3 below:\n" << endl;
readingFile(header3, Fin3); //Function call
cout << endl << endl;
cin.ignore();
return 0;
}
//the function 'readingFile'
//Pre-conditions: Reads the contents from the files of Headlines1,2,and 3
//Post-conditions: Prints out the contents.
void readingFile(string[], ifstream &infile)
{
char next;
infile.get(next);
while (!infile.eof()) //Reading until EndOfFile
{
cout << next; //Problem is here?? I would think.
infile.get(next);
}
}
I'm just not certain if where I said the "Problem is here??" is where the problem is at. Every time I change the cout to outfile(I know, I have to change the parameters within the function header) once doing that I open the outfile and the file is blank.
All the files contain random words/phrases and when put together they will make a sentence. For ex. Headlines1 contains '***Queen Jennifer*'** Headlines2 contains '***has brain surgery*'** Headlines3 contains '***after eating 30 jalapenos.*'** and When put together it should read 'Queen Jennifer has brain surgery after eating 30 jalapenos.' but the files contain more words/ phrases that what I just listed in my example.
When I run the program above I am able to read all three Headline files, but they are printed in up to down form. For example, my output on my console screen would be:
Queen
Jennifer
has brain surgery
after eating 30 jalapenos
Problem:
Getting my headlines to read from left to right.
Getting them into a output file instead of the console screen.
Help Please.
You could replace this...
void readingFile(string[], ifstream &infile)
{
char next;
infile.get(next);
while (!infile.eof()) //Reading until EndOfFile
{
cout << next; //Problem is here?? I would think.
infile.get(next);
}
}
...and the calls there-to, such as...
readingFile(header1, Fin);
...with this...
void readingFile(ifstream& infile, ofstream& fout)
{
char next;
while (infile.get(next)) //Reading until EndOfFile or error
if (next != '\n') // if not newline
fout << next; // stream to file
}
...and calls ala...
readingFile(Fin, Fout);
That way readingFile is told where to write the output, and filters out the newline characters that were causing the output to appear on different lines.
This should do the trick.
#include <fstream>
#include <string>
int main() {
// Open the three files.
std::ifstream file_1("Headlines1.txt");
std::ifstream file_2("Headlines2.txt");
std::ifstream file_3("Headlines3.txt");
// Combine into one string.
std::string content;
content += std::string(std::istreambuf_iterator<char>(file_1),
std::istreambuf_iterator<char>());
content += std::string(std::istreambuf_iterator<char>(file_2),
std::istreambuf_iterator<char>());
content += std::string(std::istreambuf_iterator<char>(file_3),
std::istreambuf_iterator<char>());
// Output the string into a single file.
std::ofstream output_file("testingHeadlines.txt");
output_file << content;
}
I'm not sure what you're wanting to do about spacing between files, but that shouldn't be too hard for you to fine-tune this code for.
one possible thing why your ouput is like this is that std::ifstream::get() that you used in infile.get(next) is a non-formatted reading method which means it will not skip white spaces and newline character \n by default. so you need to check if next value is a newline like this:
if(next == '\n') continue ;
before passing it to cout << next. Thus you will skip printing a newline in your console screen.