C Search for string in heap array - arrays

Question

I use the following code to load a large hashtable on the heap.
However i dont know the right syntax to search the whole array after loading.
I suppose i can add a strcmp in the last J loop??
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
int lines_allocated = 128;
int max_line_len = 100;
/* Allocate lines of text */
char **words = (char **)malloc(sizeof(char*)*lines_allocated);
if (words==NULL)
{
fprintf(stderr,"Out of memory (1).\n");
exit(1);
}
FILE *fp = fopen("hashtable.txt", "r");
if (fp == NULL)
{
fprintf(stderr,"Error opening file.\n");
exit(2);
}
int i;
for (i = 0; 1; i++)
{
int j;
/* Have we gone over our line allocation? */
if (i >= lines_allocated)
{
int new_size;
/* Double our allocation and re-allocate */
new_size = lines_allocated*2;
words = (char **)realloc(words,sizeof(char*)*new_size);
if (words == NULL)
{
fprintf(stderr,"Out of memory.\n");
exit(3);
}
lines_allocated = new_size;
}
/* Allocate space for the next line */
words[i] = malloc(max_line_len);
if (words[i] == NULL)
{
fprintf(stderr,"Out of memory (3).\n");
exit(4);
}
if (fgets(words[i], max_line_len-1,fp) == NULL)
break;
/* Get rid of CR or LF at end of line */
for (j = strlen(words[i]) - 1; j >= 0 && (words[i][j] == '\n' || words[i][j] == '\r')j--);
words[i][j] = '\0';
}
int j;
for(j = 0; j < i; j++)
printf("%s\n", words[j]);
// Search for a string e.g "ffffffffff999999999922222222227777777777" in words[]
//
//strcmp ( string, words[j])????
//
//
//
/* Good practice to free memory */
for (;i>=0;i--)
free(words[i]);
free(words);
return 0;
}
i have tried to implement strcmp in the loop but then the program segfaults.
Used this example :
/* what is i? the number of items used in the array? */
for(x = 0; x < i; x++) {
if ( strcmp( new_name, names[x] ) == 0 ){
/* match, x is the index */
return x;
}
}
/* here with no match */
return -1;

Answer 1

As i was indenting your code i saw:
for (j = strlen(words[i]) - 1; j >= 0 && (words[i][j] == '\n' || words[i][j] == '\r')j--);
I think you meant:
for (j = strlen(words[i]) - 1; j >= 0 && (words[i][j] == '\n' || words[i][j] == '\r'); j--)
----^^^^^^^
That while would never execute what it had between braces.

Answer 2

You have a problem here:
for (j=strlen(words[i]) - 1; j>=0 && (words[i][j]=='\n' || words[i][j]=='\r'); j--);
words[i][j]='\0';
j is off by one. You shoud increment jjust after the loop:
for (j=strlen(words[i])-1; j>=0 && (words[i][j]=='\n' || words[i][j]=='\r'); j--)
{
}
words[i][j + 1] = '\0';
The extra { } is there only for readibility purposes. Otherwise if you forget the ; after the for, your code will compile correctly but with words[i][j +1 ]='\0'; being part of the loop.
Other off by one problem:
You must decrement i here:
/* Good practice to free memory */
i-- ; // <<<< decrement i here
for (;i>=0;i--)
free(words[i]);
Problem with strcmp:
Concerning your strcmp problem you probably want this:
int j;
for(j = 0; j < i; j++)
{
printf("%s\n", words[j]);
if (strcmp (words[j], "word we are lookong for") == 0)
{
// found it
}
}