Loading file into an array line by line

[ryokubaka]

In the following code, I have a function that is called in main by the line

 Array = Load_File (Filename, &Size); 

The function is suppose to do, as the title would suggest, load a file of numbers (one number per line, of N lines) into an array. I had it running at one point but got a segfault, and realize I needed to allocate memory for my array. However, as the code below is, I get an error on line 20 that says "error: invalid operands to binary * (have 'int *' and 'unsigned int'). I understand the error, but don't know how to fix it. I think I am not finding Size correctly.

I haven't coded in quite a while, so I would appreciate some help!

#include <stdio.h>
#include <stdlib.h>
#include "sorting.h"
 
long *Load(char *File, int *Size) {
 
  FILE *fp = fopen(File, "r");
  if (fp == NULL) { // check to see if file opens; if NULL, failed
    printf("Error opening file. \n");
    return 0;
  }
 
  fscanf(fp, "%d", Size); // First line of input file is designated as the total number of elements in file; store it into "Size"
 
  long *Array = malloc(Size * sizeof(long)); // Error is here
  if (Array == NULL) {
    printf("Out of memory!\n");
    return 0;
  }
 
  while (! feof(fp)) {
    fscanf(fp, "%ld", Array);  // Store all numbers into Array
  }
 
  fclose(fp);
  return(Array); // Return array for main.c
}
 

[johny10151981]

your error is on line number 15

in the function Size is defined as pointer. and you are trying multiply pointer with integer.

//long *Array = malloc(Size * sizeof(long)); // Error code
long *Array = malloc((*Size) * sizeof(long)); // correct here
 

to understand call by reference follow this link

[ryokubaka]

Thank you very much! That fixed the problem and has this function working properly.

The next function I am working on is meant to take the array that was just stored and output it entirely into a new file. I have the base for it (coded below), but my main function is saying that only 4 elements stored in the array are being copied, yet when I check the output file it only displays the last element from the array, and the rest are 0's. No errors, just functionally incorrect..

I actually think the error is not from the Save function, but still in the Load function. I'm unsure of how I can use the fscanf function to continue scanning into an array -- I think it's only scanning one by one.

 
long *Load(char *File, int *Size) {
  //long *Array = NULL;
 
  FILE *fp = fopen(Filename, "r");
  if (fp == NULL) { // check to see if file opens; if NULL, failed
    printf("Error opening file. \n");
    return 0;
  }
 
  fscanf(fp, "%d", Size); // Set Size equal to first line of the file
 
  long *Array = malloc((*Size) * sizeof(long));
  if (Array == NULL) {
    printf("Out of memory!\n");
    return 0;
  }
 
  while (! feof(fp)) {
    fscanf(fp, "%ld", Array);
    count++;
  }
 
  fclose(fp);
  return(Array);
}
 
int Save(char *File, long *Array, int Size) {
  FILE *fp = fopen(File, "w");
  int count;
  if (fp == NULL) { // check to see if file opens; if NULL, failed
    printf("Error opening file. \n");
    return 0;
  }
 
  for (count = 0; count < &Size; count++) {
    fprintf(fp, "%ld", Array[count]);
  }
  fclose(fp);
  return (sizeof(Array));
}
 

[ryokubaka]

The following is where I am at now. I believe it should be loading my array correctly, but saving the array to a separate file is not working at all (when I check output file, it is empty).

 
long *Load(char *File, int *Size) {
 
  int count = 0;
 
  FILE *fp = fopen(File, "r");
  if (fp == NULL) { // check to see if file opens; if NULL, failed
    printf("Error opening file. \n");
    return 0;
  }
 
  fscanf(fp, "%d", Size); // Set Size equal to first line of the file
 
  long *Array = malloc((*Size) * sizeof(long));
  if (Array == NULL) {
    printf("Out of memory!\n");
    return 0;
  }
 
  while (count < *Size) {
    Array[count] = fgetc(fp);
    count++;
  }
 
  fclose(fp);
  return(Array);
}
 
int Save(char *File, long *Array, int Size) {
  FILE *fp = fopen(File, "w");
  int c;
  if (fp == NULL) { // check to see if file opens; if NULL, failed
    printf("Error opening file. \n");
    return 0;
  }
  fseek(fp, 0, SEEK_END);
 
  c = getc(fp);
  while (c != EOF) {
    fputc(c, fp);
    c = fgetc(fp);
    Size++;
  }
  fclose(fp);
  return (Size);
}