C++ :: Reading And Writing Files?

Feb 20, 2015

I have to write a program that sorts names and grades from a file and output them to another.

For example:

Name: Peter Parker
Exam 1: 95
Exam 2: 90.625
Exam 3: 91.20

Name: Mary Smith
Exam 1: 65
Exam 2: 79.1234
Exam 3: 70.24

Becomes something like this in the output file:

Name: Parker, Peter
Average Score: 92.28
Grade: A

Name: Smith, Mary
Average Score: 71.45
Grade: C

I know I'm supposed to read the whole file, but I'm getting really confused on how to take the name of each student separately without recording Exam 1, 2, and 3. I'll be able to do the average score and grade on my own.

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C/C++ :: Reading And Writing Files

Jan 16, 2015

I'm messing around with reading and writing files. The first file creates a small txt file. Simple enough

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main(){
string name;
string desc;

[Code] ....

It does what it should. It creates a text file "items.txt" .... It reads as such:

dagger,a dagger,15,10,0,1,3,1,0,0,0,1,0,0,0,0,0,1

The second file is meant to read the file and place the data back into the variables. This happens, but the data crams itself into the first variable, and the rest of them collect the trash that's in memory.

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main() {
string name,desc;

[Code ....

I need to get "dagger" into name, "a dagger" into description, and each value with their perspective variable. I'm sure I need some type of "separator". Hopefully I can use the comma. Before it's over, I will have about a hundred items that will need to be read into a class of items.

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C :: Program Reading / Writing Files

Dec 10, 2013

program that I am working on. I want to use fgets() in my program so I could handle multiple words from a text(to be able to handle spaces). I get a weird result when running the program.

Code: #include <stdio.h>
#include <stdlib.h>
//#include "kim.h"
#include <string.h>
[code]....

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C++ :: Vectors And Reading / Writing Files

May 19, 2014

How to write the code for this with the following requirements:

download the text file weblog.txt

This file is an Apache web log taken from the web server for St. Mary's University. When a visitor goes to their web site, the visitor's browser makes a request to the web server to view a web page, which is a file residing on the server. Each time a page is requested by a browser, the web server records information about that request. This weblog.txt holds the details of some of those requests.

Create a non-member function to read each line of the web log file. This function must do error checking to ensure that the file is opened successfully, otherwise it must provide a message like "file not available" to the user.

Each line should then be stored in a vector such that the first element of the vector is the first line of the web log file. Because each element will hold an entire line from the file, the vector should be declared as a vector of strings.

Note: You must declare the vector in a function.

Create another non-member function to sort the contents of the vector. Make sure to pass the vector by reference or your sort will disappear when the function ends! Use the sort function with #include <algorithm> to do the sort; you do not have to write your own sort algorithm.

Create one more non-member function to write the contents of the vector to a file. Each element should be on its own line in the new file. The contents of the new file should look like the original input file once your program completes, but in sorted order.

Create a main function that calls all of your non-member functions.

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C/C++ :: Reading And Writing In Binary Files?

Jun 5, 2014

why I'm giving "Access violation reading location 0x336827B8" and also I was able to read my data but it's giving me weird stuff. I want to write the sorted grades and the average in a new disk file. so here's my code so far here's my code

#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>
using namespace std;
int avg(int sum, int size);
void swap(int *, int *);

[code]....

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C++ :: Writing / Reading String Objects To / From Files

Jul 7, 2013

I am using the code below to write a single instance of object "Employee" to a file in Binary mode. The write part seems to work fine, however when I try to read the single employee object from the file into memory I get a double free or corruption error.

I think this has to do with the fact that I am using a string data member in the Employee class but I don't understand what is going wrong. I have read that strings can vary in length and use dynamic memory allocation but if I write a single employee object to a file with data member 'name' equal to "John", it should be the exact same size when I read it back in right?

The code below works with no issues when I omit the string data member. Why is that? Where is the memory for the string object being "double released" when I read the employee object back into memory from the file?

I am using Linux Mint 15, Eclipse June and GCC 4.7.3 with the -std=c++11 option.

#include <iostream>
#include <fstream>
#include <string>

[Code].....

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Visual C++ :: Enable Writing To And Reading From Files - Unresolved External Symbol

May 13, 2013

Perhaps this can be a very popular error,

Code:

#include <stdio.h>
#include <tchar.h>
#include <iostream>
#include <string>
#include <fstream>// enable writing to and reading from files
#include <cstdlib>
#include <time.h>
using namespace std;
class Person {

[Code] .....

Error list:

Code:

Error 1 error LNK2019: unresolved external symbol "void __cdecl saveperson(void)" (?saveperson@@YAXXZ) referenced in function _main H:Cry_DevProgrammingC++Using_class_ in_ c++Using_class_ in_ c++Using_class_ in_ c++.obj
Error 2 error LNK2019: unresolved external symbol "void __cdecl displayperson(void)" (?displayperson@@YAXXZ) referenced in function _main H:Cry_DevProgrammingC++Using_class_ in_ c++Using_class_ in_ c++Using_class_ in_ c++.obj
Error 3 error LNK2019: unresolved external symbol "void __cdecl editperson(void)" (?editperson@@YAXXZ) referenced in function _main H:Cry_DevProgrammingC++Using_class_ in_ c++Using_class_ in_ c++Using_class_ in_ c++.obj
Error 4 error LNK1120: 3 unresolved externals H:Cry_DevProgrammingC++Using_class_ in_ c++DebugUsing_class_ in_ c++.exe 1

What I can do to fit this problem?

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C++ :: Using Map And Writing Files

Dec 6, 2014

I'm using maps and writing files for the first time and I get a crazy compiler error when I try to compile the following code.

//map is named schedules
// saveSchedule() is a member of the Schedule class that writes a vector of objects to disk, or is supposed to
ofstream newFile("sched.txt");
map<string,Schedule>::iterator in;

[Code] .....

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C/C++ :: Writing Data To Files To Be Called Later?

Apr 5, 2014

I am trying to use myfile to create and write user data to a file [URL].

At the moment I only want to save as .txt so that I can open it to see that it wrote to file properly.

The main issue I get is that it says the file is not open when my program gets to the error checking at the very end, a few guides mentioned that if the file was not yet created a file with the specified name would be generated in the same folder as main on the hard drive. I did try creating the file as a notepad .txt file but it still read the error. Here is the snippet concerning the writing of the file:

void WriteToFile() {
if(myfile.is_open()) {
myfile.open("userdata.txt",ios::in);
myfile<<"User name: "<<NameFirst<<" "<<NameLast<<"

[Code] ....

it compiles fine with the rest of the program and everything runs smoothly, it just isn't writing to a file.I have included <string>, <iostream> and <fstream>.

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C/C++ :: Writing Multiple Files In Nested Loop?

Jun 3, 2014

I would like to do something like this:

for (int i=0; i<5; i ++)
{
for (int j=0; j<5; j++)
{
//* CREATE A NEW FILE FOR WRITING * //
}
}

I don't know how to create a new file that doesn't get overwritten each time the loop runs.

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C++ :: Composition - Writing Programs In Multiple Files

Oct 23, 2012

So lately I've been writing multiple header and cpp files and I would always the same error when I finally #include headers in my main.cpp. This error

Code:
undefined reference to `...`

On Youtube videos I see people doing this and their work magically compiles correctly. I found out that when I #include the headers' cpp files instead, my programs would compile. I use Code::Blocks with GNU GCC compiler.

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C++ :: Reading And Writing Bit To A File

Nov 3, 2014

I'm writing a program using Huffman algorithm to compress text file. I have tested my program by just printing the printing ASCII character to file and it worked fine. However, now I have to implement using bits and my program doesn't work. It seems like I'm not reading or writing the right bits. Here is the result of my testing:In the input file I put abc the input file to compress it. Then I uncompress it the out out is aaa. Below is a snippet of how I read and write bits

Code:
class BitInput {
istream& in; // the istream to delegate to
char buf; // the buffer of bits
int nbits; public:

BitInputStream(istream& s) : in(s), buf(0), bufi(8) { }

[Code] ....

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C :: File Reading And Writing

Sep 19, 2013

I have a text file containing 500 signed decimal numbers. My task is to read each entry and convert into a 16-bit 2's complement representation (binary number) and write into the another text file.

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C :: Reading And Writing To File

Mar 19, 2013

Code:
#include <stdio.h>
struct hardware{
int recNum;
char toolName[30];
int quant;
double cost;

[Code] .....

I'm having issues with my functions working properly. I'm not sure where I'm going wrong with them and if i'm using the correct mode for the fopen.

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C++ :: Reading And Writing To The Same File?

Apr 30, 2013

Is there a way to read and write to the same file?

I'm writing a game program and I want to save the score at the end of the game to a txt file. The txt file already contains other game scores. How do I store the score without overwriting the previous scores.

I'm just using basic fstream.

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C++ :: Login With TXT Writing / Reading

Oct 28, 2013

I have to make a program that asks for your username (any)to register it. When you type it it will say something. I want to create a txt file also. so this is what I have:

#include <iostream>
#include <fstream>
using namespace std;
int main() {
int a;
{
ofstream myfile;

[Code] ....

now, how can I use the cout again to print something "Welcome to the program..."?

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C/C++ :: Reading And Writing Bit To A File

Nov 3, 2014

I'm writing a program using Huffman algorithm to compress text file. I have tested my program by just printing the printing ASCII character to file and it worked fine. However, now I have to implement using bits and my program doesn't work. It seems like I'm not reading or writing the right bits. Here is the result of my testing:In the input file I put abc the input file to compress it. Then I uncompress it the out out is aaa. Below is a snippet of how I read and write bits

public:

BitInputStream(istream& s) : in(s), buf(0), bufi(8) { }
/** Read the next bit from the bit buffer.
* Return the bit read as the least significant bit of an int.
*/
int readBit(){
int i;
if(nbits == 8){
buf = in.get();

[Code] .....

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C++ ::  Reading And Writing To File Using Same Fstream

Oct 16, 2013

I have a file of data where each line consists of 4 parameters (degree, alpha, beta and x) and a value corresponding to these, organized in increasing order of the parameters. Here's the test file I'm using:

0 1 1 0.5 3.5
1 1 1 -0.5 -0.5
1 2 0 0.2 4.5
1 3 0 0.2 -4.5
2 0 0 1.5 2.1
2 1 0 0 5.6

My code is supposed to look for a certain set of parameters (currently set to 1 2 1 1.5, which is not contained in the file) and its value. If it's there (i.e. the file contains the value for the right parameters) the program is done. If not it should calculate the value using a function JacobiPoly() and insert the wanted parameters and corresponding value in the appropriate place in the file.

I have a code in which I think everything works except the writing to file. I use an fstream so I can both read and write and open it with ios::out||ios::in. I'm also aware I need something similar to fseek in between input and output but according to [URL] .... reading and writing to the same file using the same fstream, seekp() should suffice. I'm using seekp(), but the output (in the form inout << (...)) doesn't work.

Here's the code:

fstream inout;
inout.open("inouttest.dat", ios::out | ios::in);
int degree=1, readDeg;
double alpha=2, beta=1, x=1.5, value, readAlpha, readBeta, readX, readVal;
bool foundVal=false;
streampos beforeRead=(streampos)0;

[Code] ....

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C++ :: Reading And Writing Serial Data From USB

Jan 19, 2015

I am trying to make a project using arduino to control several power surces by time, i don't want to have an lcd, that would be easyer but i don't have enought space on my project, i want to set the time and the timing for the relays via Serial

Of curse i could set it using the serial monitor on the arduino ide, but i want to make a simple program to make the pc comunicate with the arduino and make it simpler to set the time and similar stuff. How to use one of my usb ports to print and read serial data?

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C/C++ :: Reading And Writing PPM File Image

Dec 7, 2014

I am attempting to read a ppm file. When i do it i try to write it back in another file just to see how's done and i get a terrible result. I assume the problem is something with the casting i do to the variables.

This is my image class

Image:: Image(unsigned int width, unsigned int height, bool interleaved) {
buffer = new Component [3*width*height];
this->height=height;
this->width=width;
this->buffer=Component();

[Code] .....

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C/C++ :: Writing And Reading From Standard Input

Mar 18, 2015

I have an HTTP/1.0 webserver that I'm building in C that needs to exhibit CGI script functionality. Specifically, what I'm having trouble with is that I have two processes: process 1 is the webserver, process 2 is the CGI script. I fork in the webserver, and then call exec to run the CGI script (specifically, I used execv()). I've read from the CGI specifications in the RFC that in the case of a webserver receiving a POST request, the CGI script should read the arguments for the POST request from stdin. However, when I write to stdin, it simply echoes what was written to the terminal window and when the CGI script tries to read from stdin, it blocks.

So, with all that said, I'm pretty sure there is some simple conceptual explanation to my problem, but I can't figure it out. Do I need to use pipes or some form of interprocess communication to send the data from the webserver to the CGI script, or can it just be done with stdin (and possible stdout)?

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C :: Writing Binary Data Or Reading From A File

Mar 6, 2013

I am having problems either writing data to a binary file or reading from the file. Through the process of elimination I am posting the code where the data is written to file to see if I can eliminate that as an option. I know the data is being processed correctly because, through the use of another function, I can view the data.

I also know that fwrite must be including some padding because the file size ends up being 576 bytes after it is written instead of 540 bytes (the size it would be if no padding is used). Here is my struct:

Code:

typedef struct {
char teams[25];
float wins;
float losses;
float pct;
int runsScored;
int runsAgainst;
} STATISTICS;

Here is where I initialize it:

Code:
STATISTICS stats[12] = {
{"Anaheim Arrays", 0.0, 0.0, .000, 0, 0},
{"Pittsburg Pointers", 0.0, 0.0, .000, 0, 0},
{"Indianapolis Integers", 0.0, 0.0, .000, 0, 0},

[Code] ....

And here is the function that writes my data. The sA array is only used to change the scheduled games based on the variable week.

Code:
void schedule(STATISTICS stats[]) {
FILE *f;
int sA[12], week = 0, runsPerGameA = 0, runsPerGameB = 0, runsAgainstA = 0, runsAgainstB = 0;
int index, a = 0, b = 1, i = 0;

[Code] .....

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C++ :: Reading And Writing Data In Text File

Jan 5, 2015

Code to write data(Double type e.g 12345.67891) in text file like pattern given below. Remember to put tab between each column.

-----------------------------------------------------
Column1 Column2 Column3
Value 1 Value 2 Value 3
Value 4 Value 5 Value 6
Value 7 Value 8 Value 9
----------------------------------------------------

& Also how to read data from this file.

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C++ :: Reading / Writing File On Multiple Threads?

Aug 7, 2013

I'm currently working on a server for handling clients in a 2d online game and I wrote some regular fstream file code for handling the file that stores their information and I was about to implement it into the server, then I realized there might be a problem having it open multiple times concurrently, so I googled it and came up with
posts like

[URL]

I'm wondering if I can just treat it like everything else or will I have to do something specific for opening on multiple threads?

p.s. I did read those posts but I'm very new to multithreading

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C++ :: Reading File Then Writing To It If Duplicate Not Found

Jan 22, 2014

I'm having issues with writing to a file. more precisely, i'm trying to determine if a set of numbers are in the file. if they are already in it, don't write to the file. if not, write to the file. My problem is my program is writing all numbers, even duplicates. The sort is working.

#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
//Counter Stats
int STR;

[code].....

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C++ :: Writing And Reading Binary Data In FORTRAN?

Apr 2, 2013

I am writing a double number in Binary format to the console of program A (in FORTRAN) with the following code:

Code:
REAL*8 A
A = 12.54
INQUIRE(6, name = xstring)
OPEN(1,file=xstring, access='stream',action='write')
WRITE (1) A
CLOSE(1)

And trying to read that number by program B (in C++) which is connected to program A by anonymous pipes. Following is the reading part of program B:

Code:
#define BUF_SIZE 5000
BOOL bSuccess = FALSE;
char Buf[BUF_SIZE];
DWORD dwRead;
for (;;) {
bSuccess = ReadFile( V_hChildStd_OUT_Rd, Buf, BUF_SIZE, &dwRead, NULL);
if( ! bSuccess || dwRead == 0 ) break;
}

Note: V_hChildStd_OUT_Rd is a handle to the output of program A.

After running the program although bSuccess becomes TRUE, Buf array does not include the number (12.54) that I am expecting. If I do the same process without using the binary format it works fine and I can read the number. I know somethings wrong with the writing or reading of binary data but I do not know what it is.

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