hashing with linked list

[agentsmith]

#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;
}

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.

[tabstop]

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.