How do I fill a string array from a textfile using double pointers?

Question

I'm trying to read a file and save the strings in an array using pointers, but I'm having problems. Can someone give me suggestions of what to do?

// not allowed to change these two rows
char **Lines;
Lines = (char**)malloc(sizeof(char*)*maxLines);

...

FILE *fp;
fp = fopen(fileName, "r");     // fileName already exists here
int i=0, j=0;

while(i<maxLines){
    Lines[i] = (char*)malloc(maxLength * sizeof(char)); 
    i++;
}

// No string will be longer than "maxLenght" so no buffer is used.
while(fgets(Lines[j] , maxLength, (FILE*) fp) != NULL && j < maxLines) 
{
        j++
}

I want to fill "Lines" with each string in the file. I keep getting segmentation fault. Thanks!

Maybe have a look at stackoverflow.com/questions/5935933/… — user3657941
– user3657941, Commented Nov 15, 2019 at 18:32
You allocated an array of pointers (one for each line) but didn't allocate memory for any of them. You can read each line into a generous buffer first so you know how long it is, then allocate enough memory and copy it. — Weather Vane
– Weather Vane, Commented Nov 15, 2019 at 18:35
This question, or a variant of it, gets asked multiple times a day. Please search before asking! — dandan78
– dandan78, Commented Nov 15, 2019 at 19:00
I don't know if it accounts for the segfault, but in the second loop i < maxLines should be j < maxLines. — Weather Vane
– Weather Vane, Commented Nov 15, 2019 at 19:21

Imtiyaz Shaikh · Accepted Answer · 2019-11-15 19:14:01Z

1

In your second while loop replace "||" with "&&".

The loop in this case continues to execute even when after maxlines has reached.

edited Nov 15, 2019 at 19:14

answered Nov 15, 2019 at 19:06

Imtiyaz Shaikh

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3 Comments

user12379675 Over a year ago

That was a silly mistake by me. thanks. I'm still getting segment faults tho :(

Imtiyaz Shaikh Over a year ago

Now that you are using j for fgets, use j<maxlines. i is already at maxlines.

user12379675 Over a year ago

This silly issue and another issue with that WeatherVane solved fixed it. thanks!

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