Reading words into double pointer

**Otto45** · 04-22-2013

I have a double pointer, and I need to read words into it. Here's what I have so far:

Code:

while(fscanf(keywordFile,"%s",keyinputter)==1){    
  keys_cnt++;
}
  keywords = (char**)calloc(keys_cnt,sizeof(char));
  rewind(input);
  int y=0;
  while(fscanf(keywordFile,"%s",keyinputter)==1){
    keywords[y] = strdup(keyinputter);
    y++;
  }
printf("%s\n",keywords[0]);

keyinputter is an array of size 30. The first while loop finds the number of words in a file so that I can calloc the correct amount of space for the double pointer, keywords. The second while loop is supposed to read the words into the double pointer, but when I run a print statement to print the string at keywords[0], it only prints null and not the word. Am I assigning the strings to the double pointer in the wrong way?

**Adak** · 04-22-2013

keys_cnt is counting the words, rather than the number of chars. So your allocation is for the number of words, not the length of one word.

Your logic should be:
count the number of words

allocate the first array of pointers (1st dimension)

rewind the file pointer

read the first word into a temp string variable - not the array yet

get the length of that string (why not strlen()?)

allocate the length of that string + 1 for the end of string char to be put there
(the 2nd dimension)

copy the word from the temp string variable, into the array of pointers

Make sense?

**Otto45** · 04-22-2013

Yes, that makes sense. How would I allocate only the first dimension individually, and same question for the second? Would allocating for the first just be:

Code:

keywords = (char*)calloc(keys_cnt,sizeof(char))

and 2nd dimension would be:

Code:

keywords[y] = (char**)malloc(strlen()+1)

**Adak** · 04-22-2013

Originally Posted by Otto45

Yes, that makes sense. How would I allocate only the first dimension individually, and same question for the second? Would allocating for the first just be:

Code:

keywords = (char*)calloc(keys_cnt,sizeof(char))

and 2nd dimension would be:

Code:

keywords[y] = (char**)malloc(strlen()+1)

What's wrong with malloc()? The end of string char marks the end of every word, and there is nothing to "calloc()".

sizes should be key_cnt * sizeof(char*) I have no idea why you named it key_cnt

malloc() returns a void pointer, so there is no need to cast the return from it, to any type - it's done for you. (and oddly, it can hide an important error).

Give that a try.

**AndiPersti** · 04-22-2013

I recommend working throuh a tutorial like A Tutorial on Pointers and Arrays in C before you continue with your program.

Bye, Andreas

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