FAQ Database Discussion Community


C++ How to read txt file and retrieve numerical values, apart from string (and vice versa)

c++,fstream,ifstream
I have been teaching myself C++, and searching for how to do this. Let me give an example to clarify my intention. Here is a txt file, and the content is following. Matt 18 180.0 88.5 Angela 20 155.5 42.2 Each row has information about a person's name, age, height...

ifstream attempting reference to a deleted function

c++,c++11,ifstream
I'm writing a code for a virtual tournament. The problem is that team class has an ifstream object, I understand that stream objects do not have copy constructors, therefore i converted playing8 from vector of team objects to pointer to object, So that team objects will not be copied.But now...

Retrieving File Data Stored in Buffer

c++,performance,buffer,ifstream,large-files
I'm new to the forum, but not to this website. I've been searching for weeks on how to process a large data file quickly using C++ 11. I'm trying to have a function with a member that will capture the trace file name, open and process the data. The trace...

How to write from file to string

c++,file,ifstream
I am new to C++ and I'm having trouble understanding how to import text from a file. I have a .txt file that I am inputting from and I want to put all of the text from that file into a string. To read the text file I am using...

Compiler throws an exception when trying to compile code containing binary ifstream

c++,ifstream
I am running into a problem with the accessing a binary file via the input file stream class (ifstream). My approach starts with the following calling function: void ReadFile(vector<string>& argv, ostream& oss){ string FileName = argv.at(2) + "INPUT" ; ifstream BinFile ; OpenBinaryFile(FileName, BinFile) ; return ; } The called...

C++ - ifstream and array functions

c++,error-handling,ifstream
I have a problem with a function that is having ifstream and string in it. This my code: #include <iostream> #include <time.h> #include <iomanip> #include <stdlib.h> #include <fstream> #include <string> const int ArrayMax = 100; int DisplayMenu(); void LoadNames(); void ReadFile(ifstream& , ifstream& ,string[],string[]); using namespace std; int main() {...

ifstream variable not reading correct character 1

c++,boolean,ifstream
I have an issue with the following code snippet. I have a file referred to with the character array FileName. The file could be basically anything, but in my case it is a file the contains some irrelevant text on the first line and then some lines that start with...

Vector of input streams?

c++,vector,ifstream,cin,istream
Im looking to create a vector that stores a list of different input streams including cin and a few text files. So far I have this. vector<istream> inStreams; vector<istream>::iterator streamsIterator; streamsIterator = inStreams.begin(); streamsIterator = inStreams.insert(streamsIterator, cin); ////this has error! for (char i = 1; argv[i] != NULL; i++) {...

How do I stop reading a line when I encounter a whitespace?

c++,c,ifstream,readfile
I'm opening a file and reading it using getline(x,y) currently but I want to stop reading the line when I encounter a whitespace and then continue reading from there. Thanks

ifstream stopped working in eclipse

c++,eclipse,ifstream
I have a C++ project that I haven't used in a year. It used to run perfectly, opening files with: Matrix pmatrix; pmatrix.readFromFile("pmtx.txt"); and in the function: void Matrix::readFromFile(string filename){ ifstream tmfile; tmfile.open(filename.c_str()); if (!tmfile) { cout << "unable to open tm file"; //return 1; } etc } It keeps...

Splitting string into smaller strings from text input

c++,string,ifstream
Reading in a text file to a C++ program I'm working on, and storing each string in a node for a double-linked list. Problem is, I don't know how to split up a line into smaller strings, separating them where the space is. For instance, one input is "Duck Donald...

IO on file descriptors

c++,linux,file,ifstream,file-descriptor
I just ran into the following behavior and would like to know the reasons behind it: Assume a simplified program like that ... { std::ifstream in(argv[1]); assert(in.good()); while (std::getline(in, line)) { // Area 1 } in.close(); } { std::ifstream in(argv[1]); assert(in.good()); while (std::getline(in, line)) { // Area 2 } in.close();...

How to write to middle of a file in C++?

c++,fstream,ifstream,ofstream
I think this should be quite simple, but my googling didn't help so far... I need to write to an existing file in C++, but not necessarily at the end of the file. I know that when I just want to append text to my file, I can pass the...

C++: Input file (data of unknown size) into vector issue

c++,vector,filestream,ifstream
I'm trying to put a file with two columns of data, x and y, into two vectors, one only containing x and the other only containing y. No column headers. Like this: x1 y1 x2 y2 x3 y3 However, when I run this code, I encounter an error: (lldb) Can...

ifstream no conversion from char to char exists error

c++,char,ifstream,getline,c-strings
int main() { char buffer[1024]; ifstream dataFile ("./data.dat"); while(buffer) { localHouse->location = dataFile.getline(buffer, 1024); } } This throws the error: No suitable converion function from "std::basic_istream<char, std::char_traits<char>>" to "char" exists. It continues to throw this error if I use a pointer to buffer instead. as far as I can...

Reading from file in c++ ifstream

c++,oop,while-loop,ifstream
I am working on a program that reads from a file and pushes back the contents of that file into a vector. It will read until the file reaches a space and push that string into a vector, then continue after the space. I have written this code. ifstream inFile;...

Problems of passing a const char* address of file to an ifstream object

c++,string,oop,ifstream
An ifstream object takes a const char*. I am giving my ifstream object the path of my file ifstream in_file("E:\\myfile.csv"); //File opens If i want to want to pass a string containing the address of my file i would have to convert it to a const char* first, i do...

What is the difference between std::ifstream::in and std::ios::in? (obviously as an openmode flag for an std::ifstream in C++)

c++,ifstream
I used SymbolHound to look for ressources on the web comparing the two but couldn't find anything. Looking for std::ifstream::in's declaration and definition in VS13 brings me to basic_ifstream's. Looking for std::ios::in's brings me to basic_ios's. It seems std::ios::in is more widely used. Thanks in advance, Hans...

Read/Write to PPM Image File C++

c++,ifstream,ofstream,ppm
Trying to read and write to/from a PPM Image file (.ppm) in the only way I know how: std::istream& operator >>(std::istream &inputStream, PPMObject &other) { inputStream.seekg(0, ios::end); int size = inputStream.tellg(); inputStream.seekg(0, ios::beg); other.m_Ptr = new char[size]; while (inputStream >> other.m_Ptr >> other.width >> other.height >> other.maxColVal) { other.magicNum =...

C++, getline() cant properly load all characters

c++,get,ifstream,getline
I have text file filled with characters similar to these: ¶§čç†8,ĄyŚ}¦PÜĎY®Všw†inmĘkÚhíU”*Q–­Ö}W"ĄőK=Ć“7ßńĎ_0§ĄŚĆš‰ö¤˝†’?šŕý î7ź®xż¶¸tÔuYÖa7Ź+6cE#U+:ç˛ů€°6%·˝Î÷Ľm‹¶ĺ¬‰,Y¤r$Ň“üDGhô‚J°ÜYŽäóa·7¶1Ľľ˝.— bőľaŇ•Ďűż3«ű4°JT.ń¨kŢ&Ś6ÄmĆŕY0Ż/´~9.źÍéşď®ŁýçľURíOQS ›iJ±bĄB“˝¸&§řőUdüió^˛l˛...

std::ifstream read reading wrong size for large numbers

c++,segmentation-fault,valgrind,ifstream
I have a Problem while reading a lare chunk of binary data from a file at once. Reading the same amount of bytes bytewise is working. I have to following sample code: std::ifstream inFile; inFile.open("example.bin", std::ios::binary | std::ios::in); uint32_t bytesToAllocate = static_cast<uint32_t>(this->sectionLength)-4; this->binaryData = new uint8_t[bytesToAllocate]; inFile.read(reinterpret_cast<char*>(&this->binaryData), bytesToAllocate); if i...

Is it better to read an entire file in std::string or to manipulate a file with std::ifstream?

c++,string,ifstream
I am actually developing scientific C++ simulation programs which read data, compute lots of values from them and finally store the results in a file. I wanted to know if reading all the data at once at the beginning of the program is faster than keep accessing the file via...

ifstream and ofstream or fstream using in and out

c++,fstream,ifstream,ofstream
When dealing with files, which of the two examples below is preferred? Does one provide better performance than the other? Is there any difference at all? ifstream input("input_file.txt"); ofstream output("output_file.txt"); vs fstream input("input_file.txt",istream::in); fstream output("output_file.txt",ostream::out); ...

How to integrate c++ code into working LAPACK code

c++,ifstream,lapack
I have a very simple piece of C++ code justread.cc reading numbers from a file. After the command [email protected]:~/Desktop/tests$ g++ -Wall -pedantic -o justread.x justread.cc && ./justread.x it compiles without any errors or warnings. This is the code: #include <fstream> #include <vector> int read_covariance () { std::vector<double> data; double tmp;...

segmentation fault by overloading operators with ifstream returning

c++,file,ifstream
I wrote this program in c++ in ubuntu. I wrote 2 operator overloadings like bellow. But I received "segmentation fault(core dumped)". What should I do? #include<iostream> #include<fstream> using namespace std; class Complex{ private: double x; double y; public: Complex(double a,double b){ x=a; y=b; } void setx(double a){ x=a; } void...

ifstream crashing program if file contains long words (not extreme)

c++,fstream,ifstream
im having this weird situation - im trying to read words from a file. #include <iostream> #include <string> #include <fstream> #include <stdio.h> int main(int argc, const char* argv[]) { if (argc != 2) { std::cout << "bad number of arguments" << std::endl; return 1; } std::cout << "trying to open...

C++ Finding the number of times something appears in two elements a vector of structs

c++,vector,struct,ifstream
Sorry for the confusing title, not sure how to phrase it. Basically, I have a vector full of structures consisting of some information on teams that were in the finals of some sport. The structure looks like this: struct Year{ string year; string host; string winner; string score; string runnerUp;...

how to call txt files from a directory one by one in c++ [duplicate]

c++,file-io,ifstream
This question already has an answer here: How do you iterate through every file/directory recursively in standard C++? 12 answers I know the number of files in my \data directory (n). I want to do something like that: #include <string> #include <fstream> ifstream myFile; string filename; for(int i=0;i<n;i++) {...

How do I point to an input stream?

c++,pointers,iostream,ifstream,cin
Im trying to use a pointer to point to my desired input stream depending on user decision. This is what ive got so far. string fileName = "test.txt"; ifsteam = myFile; myFile.open(fileName.c_str(), ifstream::in); istream * myStream; if (file_mode) { myStream = &myFile; } else { myStream = &cin; } string...

c++: exception error after closing console app

c++,binary,ifstream,ofstream
I am in the process of learning c++ and have a question regarding reading and writing objects to files. I created a class called Person. In my main file I created two instances of the Person class. I write instance one to a file called "person.dat" and later read it...

ifstream.read only reads half the file

c++,file,ifstream
I'm trying to make a simple image converter (ppm format to a custom one) and i'm having a problem with the ifstream.read method. Despite having this: int rows,cols, maxV; char header [100], *ptr; std::ifstream im; //open image in binary format im.open(name.c_str(), std::ios::in | std::ios::binary); if (!im) { std::cout << "Can't...

C++ getline segmentation fault, std::vector

c++,ifstream,stdvector,getline
I've been looking at this for a while in the debugger while Googling around, but I think I've stumbled upon some C++ behavior that I'm not familiar with. I'm going to give a quick outline on what I'm doing and what/where the problem is. I'll put code block below. The...

C++ ifstream exception masks for C#

c#,c++,ios,exception,ifstream
How would I convert this line from C++ to C#? std::ifstream in; in.exceptions(std::ios_base::badbit); //*THIS LINE* According to this page, the previous line of code sets a new exception mask for the stream and clears any current error state flags. I'm also guessing that it is the "second form" of std::ios::exceptions...

Fstream is draining the life out of me

c++,fstream,ifstream,ofstream
I have a code writing assignment for my computer class and it includes fstream classes. I have to write a code that manages and stores user data. I had a hard time understanding this concept in class and C++ text books just want to keep showing me IPO charts not...