Grep and search for parameters with bash script

Question

I'm trying to make a bash script to search for words in multiple text files; there are 4 parameters but the script works only if I search for all of these, not if I search only for one or more (eg word3 and word4). Word2 is a number with variable length that I don't know and I don't care about; I tried so to add a wildcard * but it gives me an error.

How can I modify the script so that I can search for one, two more or all parameters, given that word2 is not known?

#!/bin/bash

read -p "word3: " word3
read -p "word4: " word4
read -p "word1: " word1
read -p "word2: " word2
printf "Searching for ${word1}:${word2}:${word3}:${word4} $(find path/to/file -name '*.txt')"
grep -i -w "${word1}:${word2}:${word3}:${word4}" $(find path/to/file -name '*.txt') | cut -d":" -f2-

Output example is:

word1:numbervariablelenght:word3:word4

EDIT1:

*sample input
bash script.sh

word3: wordThree
word4: wordFour
word1: wordOne
word2: don't know
Searching for word1:word2:word3:word4

sample output
WordOne:somenumber:wordThree:wordFour*

Answer 1

You can find multiple patterns with egrep:

egrep -i -w "${word1}|${word2}|${word3}|${word4}" $(find path/to/file -name '*.txt')

Answer 2

Let me give you a general approach:

Look for word1 AND word2 in a file:

grep "word1" file | grep "word2"

Look for word1 OR word2 in a file:

grep -E "word1|word2" file.

Let's make an exercise out of this:

Look for word1 AND ( word2 OR word3 ) in a file:

grep "word1" file | grep -E "word2|word3"

As you see, AND can be achieved, using a pipe. OR can be achieved using extended grep ( grep -E , sometimes abbreviated as egrep ).