Segmentation fault when writing contents of dictionary to file - c

Question

The code I am working on reads in a dictionary of 45430 words and then prints to the file all the other words in the dictionary contained within each word. I am just working on getting the file MyDictionary txt file read into the char array word[45430][30] and then printing this to the words-in-words txt file. I run into a seg fault at 44946 word when I do so, but in the same while loop I am also printing to the console and all words print out properly. Why is it I am getting this seg fault for writing to the file? And why is there no seg fault writing to the console?
Code:
#include <stdio.h>
#include <stdlib.h>
#include <wchar.h>
#include <string.h>
//char ***alloc_array(int,int);
int main(void){
FILE *fr; //declare file read file pointer
FILE *fp; //declare file printed file pointer
//char array to read in up to 30 chars
char line[31];
long numwords=45430; //number of words in dictionary
int maxlength=31; // the longest string in dictionary (30 chars)
long i; //counts up to 45430
//allocate space for 45430 words at a max length of 30 chars (1 extra char for "\0")
char ***word = calloc(numwords, sizeof(char **));
for(i = 0; i != numwords; i++) {
word[i] = calloc(maxlength, sizeof(char *));
}
//Open MyDictionary.txt and determine if there is an error or not
fr = fopen ("MyDictionary.txt", "r"); // open the file for reading
if(fr==NULL){
printf("\nError! opening input file");
exit(1); //Program exits if file pointer returns NULL.
}
//Open words-within-words.txt and determine if there is an error or not
fp = fopen ("words-within-words.txt", "w"); // open the file for reading
if(fp==NULL){
printf("\nError! opening output file");
exit(1); //Program exits if file pointer returns NULL.
}
int j=0; //counts to 30 for max length
i=0;
while(fgets(line, 40, fr) != NULL){ //get a line, up to 40 chars from fr and put first . done if NULL
for(j=0;j<30;){
word[i][j]=&line[j];
j++;
}
j=0;
printf("\n%s",word[i][j]); //print out each word of dictionary to console on its own line
/*
if((i>4 && i<8)||(i>45428)){
fprintf(fp,"\nanalyze:word[i][0]=%s\tword[i][2]=%s\ti=%li",word[i][0],word[i][2],i+1);
}
*/
fprintf(fp,"%s",word[i][j]); //print out each word of dictionary to words-in-words on its own line
i++;
}
fclose(fr); //close the files prior to exiting
fclose(fp);
return 0;
} //main

Answer 1

char ***word = calloc(numwords, sizeof(char **));
for(i = 0; i != numwords; i++) {
word[i] = calloc(maxlength, sizeof(char *));
}
You've got one too many levels of indirection. You are storing a list of words. A word is a char *, so a list of words would be char **.
char **word = calloc(numwords, sizeof(char *));
for (i = 0; i != numwords; i++) {
word[i] = calloc(maxlength, sizeof(char));
}
This will then necessitate changes to the rest of your code. You can get rid of j entirely. This:
for(j=0;j<30;){
word[i][j]=&line[j];
j++;
}
Becomes:
strcpy(word[i], line);
And this:
j=0;
printf("\n%s",word[i][j]);
fprintf(fp,"%s",word[i][j]);
i++;
Becomes:
printf("%s\n", word[i]);
fprintf(fp, "%s\n", word[i]);

Answer 2

'word' should be an array of pointers, so the right type is char **, not char ***.
Each entry in the array is a pointer to a buffer of characters:
char **word = (char **)calloc(numwords, sizeof(char *));
if (!word)
// exit with error
for (i = 0; i != numwords; i++) {
word[i] = (char *)calloc(maxlength, sizeof(char)); // just allocate 31 bytes
if (!word[i])
// exit with error
}
Then a read from file can be done like this:
for (i = 0; fgets(line, 40, fr); i++) {
strncpy(word[i], line, maxlength);
printf("word %d: %s\n", i, word[i]);
}

Answer 3

To have one chunk of memory do allocate like this:
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
int result = EXIT_SUCCESS;
size_t n = 45430;
size_t l = 30;
char (* words)[n][l + 1] = calloc(n, l + 1);
if (NULL == words)
{
result = EXIT_FAILURE;
perror("calloc() failed");
goto lblExit;
}
for (size_t i = 0; i < n; ++i)
{
strncpy((*words)[i], "test", l);
}
for (size_t i = 0; i < n; ++i)
{
printf("%zu: '%s'\n", i, (*words)[i]);
}
free(words);
lblExit:
return result;
}