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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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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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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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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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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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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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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Apr 5, 2013
I am writing a program to hide files behind other files using Alternate Data Streams in Windows NTFS file systems.
The program is as follows:
Code:
#include <stdio.h>
#include <stdlib.h>
int main(void){
char hostfile[75], hiddenfile[75], hiddenFileName[15] ;
printf("Enter the name(with extension) and path of the file whose behind you want to hide another file: ");
scanf("%75s", hostfile);
[Code]...
The complier is showing error as "Extra Perimeter in call to system" but I am not getting where?
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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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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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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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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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Jul 10, 2013
I have written the following code to add data to text files which are required to store 3D scan data (I have to calculate the y-coordinate). My code seems to work except that it stops working when I want to create more than ten text files i.e. the directory I am trying to store them in will not hold any more than ten text files. Code is shown below.
#include <string>
#include <locale>
#include <iomanip>
#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;
[Code] ....
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Mar 21, 2013
Im programming client/server app that client provide the file name then the server send it to client then the client will save it ..this is part of code in client
Code:
char buffer[1024];
printf("FIle is being downloaded ...
");
printf("%s
",buffer);
}
[code],...
So i have 2 problems ::
1st one is when i write to file the file permission i cant define it with data type mode_t ,so the file does not open at all after creation...
2nd one is: the data in buffer is less than 1024 ,the data wrote to buffer but with garbage data . How to make the file read only the real data with garbage ??
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Aug 16, 2013
I a want to write a code to convert a string into binary data for that i wrote a code its working perfectly but there is one problem , some of the binary data is written in 7bit and i want to convert it to 8 bit by adding 0 to the last.
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
[Code]....
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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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Aug 19, 2013
I am trying to write one data to my file(myfile.#abc).
Code:
FILE * pFile;
int iLast Col=3;
fopen_s (&pFile,_T("myfile.#abc"), "w+");
fwrite ((char *)&iLastCol,1,2,pFile);
fclose (pFile);
Inside file ia getting a value like this
[ETX][NULL]
What is mean by ETX,Like that some other variable I amgetting [SUB],[STX]etc.what is this?
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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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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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Jan 7, 2015
I'm facing a problem regarding data entry in file.I'm making arrays which terminates when I press enter key but problem is that character at 0 index is not in file while rest of the indexes are there .. In other words,while writing on file my first character of any array got missed and did'nt present in the file ..
char CNIC[10000];
std::fstream file1;
cout<<"Enter CNIC's >>>>>>>>>>> "<<endl;
file1.open("Nadra database.txt",std::fstream::in | std::fstream::out | std::fstream::app);
if(!file1) {
cout<<"File was not open";
} else {
for(int i=0;i<11;i++)
[code]....
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Apr 21, 2012
Basically, I want to write an image to disk in parallel with an algorithm that is processing that same image. The code is really simple:
Code:
string ProcessImage(System::Drawing::Bitmap ^bmp, System::String^ targetFile) {
bmp->Save(targetFile);
System::Drawing::Bitmap^ bmp8 = BitmapConvertPixelFormat(bmp, 8); //<-- a function I wrote which converts the 32bpp I am passed into an 8bpp one
string results = Analyze(bmp8); //<--- takes a good bit of time
return results;
}
What would be the fastest way to do this? Any libraries with a code sample. I would prefer one that is within .NET or native C++ just to avoid having to link into many different libraries.
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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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Jan 27, 2014
I'm trying to read a file that is in byte format then append it onto another file. I'm doing this with unsigned char variable types because they're always one byte. Since the format is simply using bytes, they don't care about the character representation. However, when I read the characters in then put them out again, the '/n' character is always preceded by the '/r' character. In hexadecimal this looks like 0D0A. I have no control of this, and it seems as if it's being done automatically by the ofstream.put() function.
So, is there a way to take away this appending of characters and simply writing the raw data to the file?
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Jul 9, 2014
fstream ifs;
ifs.open ("data.str", ios::binary | ios:ut);
char *data1 = "data1";
char *data2 = "data2";
ifs.write(data1, strlen(data1));
ifs.write(data2, strlen(data2));
when i this,data2 is not going under data1, i thought each write starts on a new line?
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Mar 8, 2013
How to read and write an arbitrary number of bits from/to a file stream.
For instance, how to repeatedly read 9 bits from a file, then change to 10 bits, then 11 bits, and so on?
Obviously one way is by doing a lot of bit shifting, and masking. But honestly, I'm too dumb to get it right. Then I thought about using std::bitset and std::vector<bool>.
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Oct 20, 2013
When you have to write data on a file in binary mode multiple times (without closing the file), is the put pointer left where you ended writing the last time, or do you have to use tellp() or seekp() again and again to make sure you write at the right place?
I would have the same question about the get pointer, does he stay in place after you're done reading something (without closing the file, of course), or do you have to set it back at the right place with seekg() ??
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