Displaying information from an external file in C - c

Question

How do I read in an external file and then either print the whole text or selected lines?
FILE *fp;
fp=fopen("c:\\students.txt", "r");
I understand that reads the file but after that I am lost. Help please!!!
Do I need to read in binary or is text file acceptable?

Answer 1

You get a pointer to the file stream with fopen()
fread() will only return the amount of actual data that the program
could find inside your .txt file - It's very misleading. The main use is getting the number of elements for your loops. You can upload a file into your program, and print it on the screen without ever touching this function, if you know exactly what the file should already have. Only use this if you don't know what's in your file.
getline() is your go-to for printing out a specific line. No way around this one, and you'll need the specific library for it.
Here's an Example Code I wrote while doing a self-study on this, just showing how each of these are used, and printing out on BOTH the program, and a separate txt file outside the program. It doesn't have getline() however.
/*
Goals:
Create an array of 5 values
Input 5 vales from a pre-created file, into the new array
Print out the 5 values into another file.
Close the file.
*/
#include <stdio.h>
#include <stdlib.h>
#define DATAFILE "E:/Data.txt"
#define REPORT "E:/Report.txt"
//prototypes
FILE *Open_File();
void Consolodate_Array(int a_array[], FILE *file_pointer);
void Print_File(int a_array[], FILE *report_pointer);
void end_function(FILE *file_pointer, FILE *report_pointer);
int main(int argc, char *argv[])
{
int array[5];
FILE *Datatext = Open_File();
//Declared "Datatext" to be equal to Open_File's Return value.
//FILE itself is like Int, Double, Float, ect.
FILE *ReportText = fopen(REPORT, "w");
//Did the same as above, just not in a separate function. This gives us a
//Pointer to the REPORT.txt file, in write mode instead of read mode.
Consolodate_Array(array, Datatext);
Print_File(array, ReportText);
end_function(Datatext, ReportText);
system("PAUSE");
return 0;
}
/*----------------------------------------------------------------------*/
//This function should open the file and pass a pointer
FILE *Open_File()
{
return fopen(DATAFILE, "rb");
}
/*----------------------------------------------------------------------*/
//This function should input the variables gotten for the file, into the array
void Consolodate_Array(int a_array[], FILE *file_pointer)
{
for(int i=0; i<5; i++)
fscanf(file_pointer, "%i", &a_array[i]);
}
/*----------------------------------------------------------------------*/
//This function prints out the values into the second file, & at us too.
void Print_File(int a_array[], FILE *report_pointer)
{
for(int i=0; i<5; i++)
{
printf("%i\n", a_array[i]);
fprintf(report_pointer, "%i\n", a_array[i]);
}
}
/*----------------------------------------------------------------------*/
//This function closes the file.
void end_function(FILE *file_pointer, FILE *report_pointer)
{
fclose(file_pointer);
fclose(report_pointer);
//closes both files we worked on.
}