Creating an array with unknown size of input files - c

Question

I newer in C language. I could not solve my problem. I have a input file, let's say input.txt. We know there are 4 column on every line. Nevertheless, we do not know how many lines are there. I give you sample input.txt:
Student,James,12,65
Teacher,Jane,23,60
Teacher,Michael,30,75
Student,Erric,15,73
First column can be 2 different things like student or teacher. 2nd column will be unique. No repeated names. 3rd column will be ages of the person's. 4th column will be weights. Also, I am trying to make 2D array. So, my goal is:
arrName = {{Student, James, 12, 65}, {Teacher,Jane,23,60}, {Teacher,Michael,30,75}, {Student, Erric, 15,73}}
I am trying to create like this array. The array must be dynamically. because we do not know how many lines are there. I could not split the every line by commas. I have tried strdot. how can I parse the lines with comma, and add them into 2D array? Also, I got confused about pointers. While creating 2D array, do we have to use like char **arrPtr;? Or using like *arrPtr is enough for creating 2D array?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define COLUMN 4 //We know that there are 4 column in chars.txt file.
int main(int argc, char const *argv[]) {
char *arrName;
int nameLines;
arrName = (char *) malloc( sizeof( char ) );
FILE *FileName;
FileName = fopen(argv[1], "r");
if (FileName == NULL) {
printf("The Name file could not open!\n");
exit(0);
}
else{
char c;
while ( (c == fgetc(FileName)) != EOF ) {
if (c == '\n') {
nameLines++;
}
}
printf("%d\n", nameLines);
}
return 0;
}
I could not continue after else statement. Can you help me?

Answer 1

You got a bunch of errors in your code like this for example.
while ( (c == fgetc(FileName)) != EOF ) { -> Comparison of constant -1 with boolean expression is always true
So let's start fresh. This is how I would read a comma separated file and dynamically allocate memory to an array of ´read´ objects. It's actually less lines of code then you would expect.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define COLUMNS 4
#define MAX_STRING_LENGTH 100 //Enter the maximum characters allowed as profession and name
typedef struct theDAta{
char type[MAX_STRING_LENGTH+1];
char name[MAX_STRING_LENGTH+1];
unsigned int age;
unsigned int weight;
}theData;
int main(int argc, char const *argv[]) {
theData* allDataPtr=malloc(1); //Pointer to all entries
theData currentData; //The current read data
int currentBlock=0; //the index currently 'active'
FILE *fp = fopen(argv[1], "r");
if (!fp) {
printf("The file you provided can't be read!\n");
exit(EXIT_FAILURE);
}
while (fscanf(fp, "%[^,],%[^,],%d,%d\n", currentData.type, currentData.name,&currentData.age,&currentData.weight) == COLUMNS) {
allDataPtr=realloc(allDataPtr, sizeof(theData)*(currentBlock+1));
if (!allDataPtr) {exit(EXIT_FAILURE);} //Memory allocation failure. Ok so here i lost my pointer to the previous memory.. However we let the OS garbage collect us.
memcpy(allDataPtr+currentBlock++, &currentData, sizeof(currentData));
}
for (int x=0; x<currentBlock; x++) {
printf("Profession: %s\nName: %s\nAge: %d\nWeight: %d\n\n",allDataPtr[x].type,allDataPtr[x].name,allDataPtr[x].age,allDataPtr[x].weight);
}
fclose(fp);
free(allDataPtr);
return 0;
}
So what I do is to create a struct containing the stuff I want to populate from the file. Then I populate that object and extend the memory with the size of that object and then copy the read data to the end of that memory block.. That's basically it... Hope you get great grades :) !!
/Anders
EDIT
Was a bit bored this evening, so let's shave the code... And humm, well. This is not part of my official answer :-) but you could bling it like this (it's actually also skipping one layer of memory copy :) and the engine is 3 lines of C code if you define a line of C code delimiter as ';'->
typedef struct j{
char t[MAX_STRING_LENGTH+1];
char n[MAX_STRING_LENGTH+1];
unsigned int a;
unsigned int w;
}j;
int main(int argc, char const *argv[]) {
j* g;
int l=0;
FILE *h;
if((!(h=fopen(argv[1],"r"))||(!(g=malloc(sizeof(j))))))exit(-1);
while(fscanf(h,"%[^,],%[^,],%d,%d\n",g[l].t,g[l].n,&g[l].a,&g[l].w)==COLUMNS)if(!(g=realloc(g,sizeof(j)*(++l+1))))exit(-1);
for(int x=0;x<l;x++)printf("Profession: %s\nName: %s\nAge: %d\nWeight: %d\n\n",g[x].t,g[x].n,g[x].a,g[x].w);
fclose(h);
free(g);
return 0;
}