C :: Writing Log File In Multithread Program
Oct 20, 2014
I'm currently finishing writing some small application. I want to be able to log important information about the program execution to a logfile, and I have several questions.
First of all - I'd prefer to make the part that logs information to a file separate from the code I've already written. So, what interface should I expose to the rest of the program? Is one function void log(const char*); enough?
Another thing that came to my mind; my program runs two threads, and I want to be able to write to the log file from both threads, so the question is: Should I make sure that the writing to the file is mutually exclusive?
And if so, whose responsibility is it to make the logging to the file thread-safe? The actual part that does the logging (void log(const char*) for that matter), or the parts of the program that calls log(const char*) ?
And lastly, and probably less importantly, where is it customary to save the logfile? (the user's home folder maybe?)
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Aug 3, 2013
How do I find an error in a multithreading program (written in C)? I get an address, but when I put it into psp-addr2line, i get
??
??:0
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Mar 27, 2013
basic code for writing output of a program to a file? I can't seem to find it online and I need it to complete a project.
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Nov 18, 2013
I have been asked to write a program to grade several multiple-choice exams. The exam has less than 80 questions, each answered with a letter in the range of ‘a’ through ‘f’. The data are stored on several files such as exam1.dat where the first line is the key, consisting of a string of n characters (0<n < 80). The remaining lines on the file are exam answers, and consist of a student ID number, a space, and a string of n characters.
The program should have a while loop in the main routine to ask users input a data file name through keyboard. In this way, the program has a capability of repeatedly asking for a new data file in each while loop until users input a key word “exit”. Once “exit” is encountered, the while loop terminates and your program ends. A typical input exam data file (exam1.dat) looks like:
abcdefabcdefabcdefab
1234567 abcdefabcdefabcdefab
9876543 abddefbbbdefcbcdefac
5554446 abcdefabcdefabcdef
4445556 abcdefabcdefabcdefabcd
Apply strlen( ) or the length( ) of string to the first line of the above data file for determining the number of questions in the problem. If a student gives more answers than necessary, the extra answers will be automatically truncated. On the other hand, if a student provides less number of answers, the remaining unanswered questions are considered as being answered wrongly.
After users input an exam data file, your program should ask users to input another grade-curving file name (e.g., gradeCurving.dat). This second file contains the information to convert a percentile score to a curved grade in levels of ‘A’ through ‘E’. For instance, a grade-curving file takes the following format: a curved alphabetic grade, a space, a percentile grade served as marker.
A 90
B 80
C 70
D 60
E 50
The above information means that ‘A’ = 90 through 100; ‘B’=80 through 89; ‘C’=70 through 79; ‘D’ = 60 through 69; “E”=50 through 59; For the remaining grades, you can assign an ‘F’.
Furthermore, in each while loop in the main routine, your program should ask users to input an output file name such as score1.dat. The output file will store the scores for each student in a format: student ID number, a space, a percentile score, and a curved grade in ‘A’ though ‘E’. The program should also compute and display the following statistics for the graded answers: Average score, Maximum score, and Minimum score.
A typical output on a data file looks like:
1234567 90% A
9876543 85% B
5554446 95% A
4445556 75% C
5551112 80% B
Statistics:
Average Score: 85%
Minimum Score: 95%
Maximum Score: 75%
This Is what I have so far. It compiles fine and everything but when I input the files it says "There was an error opening the corresponding files. Check input name perhaps?" and it exits out ....
#include "stdafx.h"
#include <iostream>
#include <string>
#include <fstream>
#include <assert.h>
using namespace std;
int openfiles(ifstream& infile, ifstream& curvingfile, ofstream& outfile);
void Size(ofstream&,int,string);
[Code] ....
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Feb 17, 2014
cant write to binary file
#include <stdio.h>
#include <stdlib.h>
typedef struct {
int number;
} something;
void main() {
int numbers[10]={1,2,3,4,5,6,7,8,10,12};
[Code] .....
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Jan 30, 2013
I'm trying to make a program that you input your login info and it writes that info to a text file. Then, later on once I get my problem fixed, the program will read the info to the user. my code is as follows(the input part is a bit lengthy):
// Password Log
#include <iostream.h>
#include <fstream.h>
#include <string>
#include <time.h>
using namespace std;
ofstream login;
[Code] ....
What my problem is when I choose "Input new login info" it automatically inputs I have no clue, and calls next program.
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Jan 24, 2012
I'm creating a small port scanning app which use a port range defined by user.My problem with the code is that I find it not efficient enough meaning that it ping very slow, especially when ports are not responding meaning that I must wait for the timeout before continuing to next port.
I want to make this small app threaded. The problem here is that I'm kind of blank of how to implement threading in my program. This is my code which is a method which does the actual checking, the other part of the code is a simple button with for loop for advancing my port number.
Code:
private void ScanPort(IPAddress address, int port) {
using (TcpClient client = new TcpClient() {
IAsyncResult result = client.BeginConnect(address, port, null, null);
if (result.AsyncWaitHandle.WaitOne((int)nudTimeout.Value, false)) txtDisplay.AppendText("Port: " + port + " is open." + Environment.NewLine);
else txtDisplay.AppendText("Port: " + port + " is closed." + Environment.NewLine);
} }
I have read some basic threading tutorial but I just don't know how to implement this piece of code so I can check ports much faster.
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Feb 19, 2013
I'm having a bit of trouble learning how to multithread a socket server. I have everything working perfectly fine, but it only accepts one client (I would like multiple clients). some sort of example (I have troubles understanding some things, unless its visual).
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Oct 6, 2014
I have a class holding my data strcuture:
// Holding real time option data - should be thread safe
public class OptionRTHolder {
ConcurrentDictionary<double, Quates> book_calls;
ConcurrentDictionary<double, Quates> book_puts;
ConcurrentDictionary<double, List<Single_qoute>> transaction_calls;
ConcurrentDictionary<double, List<Single_qoute>> transaction_puts;
ConcurrentDictionary<double, int> volume_calls;
ConcurrentDictionary<double, int> volume_puts;
DateTime curr_time;
}
I get a stream of data messages, that come in order, each message carries a time and data. I have many threads in paralell pulling messages and in turn update the data strucutre as follows:
Quates and volume data are just overrun (new value overrun former values), also thier size and meta data is fixed (they don't grow post init).
Via the list I have a problem, I would want to lock only the list I am working on. so other lists can update in paralell, what I had in mind was to warp the list in order to warp the add/get calls to make it thread safety, this I think will achieve this goal and I would like to get some assertion from this forum if you may.
Here come my real problem, there are points in time I want to read/copy this structure, during this time I want to block all updating threads as I want to freeze structure in time, is that achiveable ? Idea that I had is to use something like aquire that will get a function (update/read) and a flag that will cause a lock when the read is on...something like that.
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Nov 18, 2013
Let's have global dynamic array p defined as
volatile int p[];
Let's use it in a multithread application, where every thread can change array's size by
new_p = realloc(p, new_size);
if (!new_p) exit 1;
p = new_p;
For simplify assume that we have no problems with it's size and indexing.
Expression like
int x = p[i];
is unsafe cause thread (1) takes the pointer and (2) add the index. Executing of this thread may be stoped after first step before second step. In this time other thread can realloc the array, which move it to some other place in memory. Executing second step after it will add index to wrong pointer. So we will have segmentation fault.
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Feb 6, 2014
I am writing a simple file/text parser to read a config file for some code I am working on. It's dead simple and not particularly smart but it should get the job done. The code reads a config file:
Code:
readlength=2500000
start=0
finish=25000000
cutoff=20000
samplingfreq=250000
poles=10
filterpadding=500
}
[code]....
Here is where it gets wierd. You'll notice that there is an unused variable (filepath) in the config struct. This variable is not referenced or used anywhere in the code, ever. Yet if I comment out the declaration of char filepath[1024], the code segfaults partway through the read_config() function.
My best guess is that there is a buffer overflow elsewhere and it just so happens that the memory allocated for filepath happened to be there to catch it up until now, but I can't work out where it might be happening. With the declaration commented out, the read_config() function gets as far as reading the "padding" variable before it crashes. Yet when the declaration is there, then all the variabled are read correctly and everything seems to work.
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Aug 31, 2014
One of my class assignments is to create a program that receive a .txt file containing a students name and their grades as follows: John K. 99, 87, 57, 89, 90, 95 Amanda B. Jones 100, 88, 76, 99, 86, 92 etc.. The number of students is unknown until run time. You have to take those grades and average them weighing the first (4) at 10% a piece and the next (2) at 15% each and the final at 30%. Then return an output file with the students name and their letter grade A,B,C,D,F based on their computed score. In addition, on screen it needs to display the average scores for each Q1, Q2, etc. as well as the minimum and maximum for each test on the screen. I am having a hard time in assigning the scores to a variable so that they can then be computed as an average and then used to determine a letter grade. I have begun to write the code and am a bit stuck..here's what I have so far:
Code:
//
// main.c
// Final Exam
//
[Code].....
The problem I'm having now is how to go about passing the grades to the function computeGrade and then compute the average and return that to the function.
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Mar 28, 2013
Can i edit records stored in file without rewriting whole file again .?
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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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Jan 19, 2014
How to write a program without using any type of container .
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Oct 9, 2013
Ive been writing this code all day and these errors have been killing.
Instructions:
Car Class:
Write a class named Car that has the following:
year. An int that holds the cars model year.
make. A string object that holds the make of car.
speed. An int that holds the cars current speed.
In addition, the class should have the following member functions.
Constructor. The constructor should accept the car's year and make as arguments and assign these values to a object's year and make member variables. The constructor should initialize the speed member variable to 0.
Accessors. Appropriate accessor functions should be created to allow values to be retrieved from an object's year, make, and speed member variables.
accelerate. the accelerate function should add 5 to the speed member variable each time it is called.
brake. The brake function should subtract 5 from the speed member variable each time it is called.
Demonstrate the class in a program that creates a Car object, and then calls accelerate function five times. After each call to the accelerate function, get the current speed of the car and display it. The, call the brake function five times. After each call to the brake function, get the current speed of the car and display it.
Errors: error C2061: syntax error : identifier 'stringm'
error C2533: 'Car::{ctor}' : constructors not allowed a return type
error C2511: 'Car::Car(int)' : overloaded member function not found in 'Car'
see declaration of 'Car'
fatal error C1903: unable to recover from previous error(s); stopping compilation
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
[Code].....
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Apr 22, 2014
Writing a program to calculate grades... My algorithm is long, so I only posted the part that gives me trouble. When classes== 1,2,4, or 5, the program runs fine. but it terminates when classes == 3.
if (classes==3) {
do {
cout<<"Enter the Letter grade for 1st class. (USE CAPS)"<<endl;
cin>>grade1;
[Code].....
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Nov 24, 2013
writing a program that requires exception handling. if an error occurs, i what the program to go back to the begging of the loop. i tried using break but that just makes the program crash when it receives a bad input. how do i do this? this is what i have so far (this part of the program any ways)
while (! quit)
{
// Output phone book menu
cout << endl
[Code].....
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Jan 31, 2014
I am having some trouble with my class assignment. We need to write a C program that will calculate the employee salary. There are 5 employees that will need to be calculated. We are required to use a loop also.
So far this is what I have but I am receiving errors when running the program.
#include <stdio.h>
int main() {
int clock_num; /* employee clock number */
float gross; /* gross pay for week (wage * hours) */
float hours; /* number of hours worked per week */
float wage; /* hourly wage */
/* Prompt for input values from the screen */
printf ("This is a program to calculate gross pay.
[code]....
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Aug 18, 2014
I am writing a program for a class where the user enters their age, how much money they have, and their full name. I know that I have to use the getline method to get the user's full name, and I know that I have to use cin.ignore() before that code, but i'm not sure why I have to use cin.ignore()?
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Sep 13, 2013
I'm writing a program that finds the probability of moves a Knight can make on a chess board. The program asks the user to enter the row and the column and the program is supposed to output how many possible moves the Knight can make, but the output is wrong. Example(if I enter row 1 and column 1 the output is 8 and it should be 2) I know the problem is with my if statements.
#include <iostream>
using namespace std;
int chess(int a, int b) {
int x =a;
int y = b;
int sum=0;
[code]....
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Feb 3, 2015
i need the output to display the product of every whole number from 1-3 in a table format.
this is the code i have so far. i know some brackets are missing but i just pasted the meat of the code. when i run the program i keep getting the number 1 displayed in a straight line going on forever
int multiply1 = 1;
int multiply2 = 1;
while(num1<=3)
{ // num1*num2;
//num1 = 0;
while(num2<=3)
{ Console.WriteLine(multiply1*multiply2);
if(num1>=3)
{ Console.Write();
}
}
num1++;
}
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Sep 11, 2013
im writing a program that asks the user to input a number 1-10 and will transform it into the roman numeral of that number but it seems that its not after the user inouts the number nothing will output
#include <iostream>
#include<iomanip>
using namespace std;
[Code]....
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Oct 24, 2014
write a program that computes the factorial of a number and displays it. A factorial of a number (written N!) is defined as N * (N-1) * (N-2) * (N-3) ... *1 In other words, 5! = 5 * 4 * 3 * 2 * 1 = 120 and 3! = 3 * 2 * 1 + 6.
Example of output 15 is 1.30767e+012
Can't get it to display error when user enters a number lower than 2 or higher 60.
// Program to calculate factorial of a number
#include <iostream>
#include <iomanip>
[Code].....
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Oct 31, 2014
I am writing a porgram which includes encoding and decoding a message.Now I am doing the encoding part.
The goal is to encode a message using similar approach as Caesar Cipher. But instead of alphabets, I am going to use the entire ASCII code of total 128 codes to be the base.
And it is not a simple shifting, it is a rotation. This means if you want to shift 4 units from char <DEL>, it will come back to the first code in ASCII Code which is at dec 0 char <NUL> and starts the shifting again. It won't jump if the limit of ASCII Code is reached.
Here we've got 7 different malls' names and I am going to encode them with a shift n. I think n is free to set, so here I just set it as 5. This is also called the key.
I have written something and I think it should work, but after all it doesn't. And I don't get what is wrong.
Here is my program:
#include <iostream>
using namespace std;
const int NUMBER_OF_MALLS = 7;
const int MALL_NAME_LENGTH = 13;
const int NAME_SIZE = MALL_NAME_LENGTH + 1;
void encode(int key, char plain[], int length, char encoded[]) {
for (int i = 0; i < MALL_NAME_LENGTH; i++)
[code].....
Note that I am not going to use other libraries, just <iostream>.
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Sep 9, 2014
I am executing below sample program
Code: #include<iostream.h>
#include <fstream.h>
using namespace std;
int main()
[Code]......
when i am counting the lines using wc command it is giving 1 instead of 2.
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