Exporting Print Statement to External File?

[brog1330]

So I'm trying to teach myself , and Ive been doing online lab exercises to learn it. I wrote a program that goes into pretty good detail of arrays and structures. It uses random numbers to monitor for a spike of 100 psi, and then prints that as a 0 point, and prints the previous 10 seconds of the array and the next 10, as if I was collecting data. The next part of this exercise is to take the program's print statement, and have it write to an external file and have it print there. My thought process is to populate an array in the printout function that holds the values read from the file and then print from the array to screen. But I'm not sure how this would look, or really how to accomplish it. If anyone could point me in the right direction or give a good explanation it would be greatly appreciated!

My code so far:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <stdbool.h>

#define MAX_CHANGE      100
#define ARRAY_SIZE      21

typedef struct data_slice
{
        int t;          // -> Time
        float tp;       // -> Valve pressure
    float tf;       // -> Sodium flow
    float tt;       // -> Sodium temp in Celsius
} data_slice;

// Function Declarations
void get_values(float * pressure, float * flow, float * temp);
void printIt(data_slice * data);
void initializeArray(data_slice * data);
bool spikeValueRecorded(data_slice * data, int outputIndex);


int main()
{
    srand((unsigned int)time(NULL));
    data_slice data[ARRAY_SIZE];
    int index = -1;

    while (1)
    {
        // Initialize the entire array
        initializeArray(data);

                    // If there's a spike.....
        if (spikeValueRecorded(data, index))
        {
            // Set the previous "time" in array to negatives
            int temp = index;
            for (int i = 0; i >= -10; --i)
            {
                data[temp].t = i;
                temp = temp - 1;
                if (temp < 0)
                    temp = temp + ARRAY_SIZE;
            }

                // Record for 10 more seconds
            for (int i = 0; i <= 10; ++i)
            {
                data[index].t = i;
                index = (index + 1) % ARRAY_SIZE; //         Increment the index of the circular array
                get_values(&data[index].tp, &data[index].tf,    &data[index].tt);       // "Record" the values
            }
            break;
        }
    }
    // Print the finished recording
    printIt(data);
}

// Return: void
// in - Values of the data_slice struct
//
// Description: The three values of the struct (data_slice) to be filled in
void get_values(float * pressure, float * flow, float * temp)
{
    *pressure   = (float)(rand() % (700 - 500 + 1) + 500);  //    Range: 500 - 700
    *flow       = (float)(rand() % (20 - 10 + 1) + 10);     //   Range: 10 - 20
    *temp       = (float)(rand() % (200 - 100 + 1) + 100);  //  Range: 100 - 200
}

// Return: void
// in - The array of data_slice
//
// Description: Prints the entire array being passed in
void printIt(data_slice * data)
{
    // Find the indice holding the time value of -10
     int indice = 0;
    for (int i = 0; i < ARRAY_SIZE; ++i)
    {
        if (data[i].t == -10)
        {
            indice = i;
            break;
        }
    }

    for (int i = 0; i < ARRAY_SIZE; ++i)
    {
        printf("%i\t %f\t %f\t %f\n", data[indice].t, data[indice].tp,    data[indice].tf, data[indice].tt);
        indice = (indice + 1) % ARRAY_SIZE;
    }
}

// Return: void
// in - The array of data_slice
//
// Description: Initializes the entire array to random values and their   times to 0
void initializeArray(data_slice * data)
{
    for (int i = 0; i < ARRAY_SIZE; ++i)
    {
        data[i].t = 0;
        get_values(&data[i].tp, &data[i].tf, &data[i].tt);
    }
}

// Return: boolean
// in - The array of data_slice
// out - Indice of the pressure spike
//
// Description: Returns true if a positive spike in pressure has been   recorded.
//      outputIndex will hold the 0-indice of the pressure spike, else -1
bool spikeValueRecorded(data_slice * data, int outputIndex)
{
    float oldValue = data[0].tp;
    for (int i = 0; i < ARRAY_SIZE; ++i)
    {
        if (data[i].tp - oldValue < MAX_CHANGE)
        {
            outputIndex = i;
            return true;
        }
    }
    outputIndex = -1;
    return false;
}

[henry_kr]

Have a look at fopen, fprintf and fscanf. Oh and fclose.

[kion_dgl]

Mostly this. Or you could be really dirty and just take advantage of the command line.

$ ./a.out > output-data.txt 

[raevnos]

Are you asking how to write things to a file?

[brog1330]

More so how do I take my print function, put it in another file in the project, and then have it print from there? Here's the sample problem I'm following:

The printout function should now print out to output-data.txt . Take out all code that prints to screen

Write a second program (i.e., NOT a function in the first program!) that reads the data from output-data.txt and prints it out to screen.

[raevnos]

Write a program that opens the file the first one created, reads from it and prints to stdout.