Read numbers from text file and use them as input - c

Question

I have this text:
0 0 0 0 0 1
0 0 0 0 1 1
0 0 0 1 0 1
0 0 0 1 1 1
I want to read the first 5 numbers from each line and then use them as inputs in a function.
I'm new to c and have only accomplished this code that doesn't do much, if anything really.
int v,o;
FILE *mydata;
if ((mydata = fopen("testinputs.txt", "rt"))==NULL)
{
printf ("file can't be opened'\n");
exit(1);}
fclose(mydata);
How do i complete it?
Thank you.

Answer 1

Well, assuming your file is called "input.txt", then this is all you need to do:
#include <stdio.h>
#include <stdlib.h>
#define LINE_LEN 100
int main ( void )
{
char line[LINE_LEN];
int sum, i, read_cnt, numbers[5];//sum and i are there for my example usage
FILE *in = fopen("input.txt", "r");//open file
if (in == NULL)
{
fprintf(stderr, "File could not be opened\n");
exit( EXIT_FAILURE);
}
while((fgets(line, LINE_LEN, in)) != NULL)
{//read the line
//scan 5 numbers, sscanf returns the number of values it managed to extract
read_cnt = sscanf(
line,
"%d %d %d %d %d",
&numbers[0],
&numbers[1],
&numbers[2],
&numbers[3],
&numbers[4]
);
//check to see if we got all 5 ints
if (read_cnt != 5)
printf("Warning: only read %d numbers\n", read_cnt);//whoops
//just an example, let's add them all up
for (sum= i=0;i<read_cnt;++i)
sum += numbers[i];
printf("Sum of numbers was: %d\n", sum);
}
return EXIT_SUCCESS;
}
With this input.txt file:
1 2 3 4 5
2 2 2 2 2
1 23 2 3 4
12 23
This gives us the following output:
Sum of numbers was: 15
Sum of numbers was: 10
Sum of numbers was: 33
Warning: only read 2 numbers
Sum of numbers was: 35
That should be more than enough to get you started

Answer 2

Here is a small code to read character by character and store only the wanted numbers:
C Code:
#include <stdio.h>
#include <stdlib.h>
int main()
{
int c; // Character read from the file
int cpt; // Counter (to get only 5 numbers per line)
int i,j; // Array indexes
int data[4][5]; // 2D integer array to store the data
FILE *f; // File
if ((f = fopen("file.txt", "r")) == NULL) // Open the file in "read" mode
{
printf ("file can't be opened'\n");
exit(255);
}
// Counter and indexes initialization
cpt=0;
i=0;
j=0;
// Read the file till the EOF (end of file)
while ((c = fgetc(f)) != EOF)
{
// If 5 numbers read, go to new line, first index in the data array and to the next line in the file
if(cpt==5)
{
i++;
cpt=0;
j=0;
while(c != '\n' && c != EOF)
c=fgetc(f);
}
// If a number is read, store it at the right place in the array
if(c>='0'&&c<='9')
{
// Convert character to integer (see ascii table)
data[i][j] = c-'0';
j++;
cpt++;
}
}
// Display the array
for(i=0;i<4;i++)
{
for(j=0;j<5;j++)
printf("%d ", data[i][j]);
printf("\n");
}
fclose(f);
}
And here is the output:
0 0 0 0 0
0 0 0 0 1
0 0 0 1 0
0 0 0 1 1
Now you can use your 2D array, for example if you want a variable a to have the 2nd line, 3rd number, you'd do : a = data[1][2]
Don't forget arrays start at index 0
Hope this helps...

Answer 3

It might help you:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
FILE *datafile;
int main()
{
char line[100],*ch;
int count;
datafile = fopen ( "my.txt", "r");
while ( fgets(line , sizeof line , datafile) != NULL )//fgets reads line by line
{
count = 0;
ch = strtok ( line , " ");
while ( count < 5 && ch != NULL )
{
printf("%d ",*ch - 48 );//*ch gives ascii value
//pass to any function
count++;
ch = strtok ( NULL, " ");
}
}
return 0;
}
The above program passes integer by integer.