Segmentation fault reading random lines of text? - c

Question

I have read a lot documentation about this subject but i still have some problem about this,ı know what pointer is but when i try to use ı am facing some problem ,at below code,txt file includes just one words at every line.I tried the read random line from text and return to main function cause after i will need this).And i print it in main function ,please can you help me which section should i change in this code?(When ı try to run this the error message is Segmentation fault (core dumped))
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
char word(char *file, char str[], int i);
int main() {
char buf[512];
char j = word("words.txt", buf, 512);
puts(j); // print random num
}
char word(char *file, char str[], int i) {
int end, loop, line;
FILE *fd = fopen(file, "r");
if (fd == NULL) {
printf("Failed to open file\n");
return -1;
}
srand(time(NULL));
line = rand() % 100 + 1; // take random num
for (end = loop = 0; loop < line; ++loop) {
if (0 == fgets(str, sizeof(str), fd)) { // assign text within a random line to STR
end = 1;
break;
}
}
if (!end)
return (char*)str; // return the str pointer
fclose(fd);
}

Answer 1

You reopened the file, this might be the case. You don't close the file if it returns in if(!end) part the fd is not closed.
And the function takes char but actually needs char *
char word(char *file, char str, int i);
int main() {
char * buf = malloc(sizeof(char)*512);
char *words = "words.txt";
char* j = word(words, buf, 512);
puts(j); // print random num
}
char word(char *file, char str[], int i) { // FIX HERE
int end, loop, line;
FILE *fd = fopen(file, "r"); //
if (fd == NULL) {
printf("Failed to open file\n");
return -1;
}
srand(time(NULL));
line = rand() % 100 + 1; // take random num
for (end = loop = 0; loop < line; ++loop) {
if (0 == fgets(str, sizeof(str), fd)) { // MAIN PROBLEM, PUT A CHAR* TO STR.
end = 1;
break;
}
}
fclose(fd); // YOU DIDN'T CLOSE IF IT RETURNED BEFORE
if (!end)
return str; // return the str pointer
//NOTHING IS RETURNED HERE
return str;
// I guess the problem is here, you return nothing and the function finishes, and you try to write that nothing with puts function which may cause a seg fault.
}```