hashing with linked list

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

typedef struct List { char *word; struct List *next; } List;

#define HASHSIZE 65536
#define LEN 50

static struct List *hashtab[HASHSIZE];

static FILE *open_file (char *file, char *mode)
{
  FILE *fp = fopen (file, mode);

  if (fp == NULL){
    perror ("Unable to open file");
    exit (EXIT_FAILURE);
  }
        return fp;
}

int is_punctuation (int a)
{
    return a == ' ' || a == '\n' ||
          a == EOF || a == ',' ||
          a ==';' || a =='.'||
          a =='!' || a =='?' ||
          a ==':' || a =='`';
}

unsigned rot_hash (void *key, int len)  // Rotating hash
{
        unsigned char *p = key;
        unsigned h = 0;
        int i;
       
        for (i = 0; i < len; i++)
                h = (h << 4) ^ (h >> 28) ^ p[i];
        return h % HASHSIZE;
}

struct List *lookup (char *s, int x)
{
        struct  List *np;
       
        for (np = hashtab[rot_hash(s, x)]; np != NULL; np = np -> next)
                if (strcmp (s, np -> word) == 0)
                        return np;
                return NULL;
}

int install (char *name, int x)
{
        struct List *current_list;
        struct List *new_list;
        unsigned int h = rot_hash (name, x);
        if ((new_list = malloc (sizeof (List))) == NULL)
                return 1;
        current_list = lookup (name, x);
        if (current_list != NULL)
                return 2;
        new_list -> word = strdup (name);
        new_list -> next = hashtab[h];
        hashtab[h] = new_list;
        return 0;
}
               
       
int main (int argc, char *argv[])
{
        int x, i, k, count, comp;
        char a, ans, word[LEN];
        x = 0;
        k = 0;
        FILE *fp = open_file (argv[1], "r");
        do{
                a = fgetc (fp);
                if (is_punctuation(a)){
                        if (x != 0){
                                word[x] = '\0';
                                k = install (word, x);
                                printf ("%d\n", k);
                                x = 0;
                                }
                }else{
                        word[x] = tolower(a);
                        x++;
                        }
        } while (a != EOF);
        fclose (fp);
        return 0;
}

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i need it to read in a value into a hashtable and if there is a collision it inserts the word into a linked list. can anyone tell me if my install func is correct as i can't think of a way of testing it until i do search function later.

Your lookup function is correctly written, but not correctly indented (the return NULL statement is not part of the for loop). Otherwise, everything looks fine.