[SOLVED] How to find all lines which contain at least one of a set of words as a prefix

Issue

I have a text file of words, one per line, called A.

I have another text file B.

How can I find all lines in B what have at least one of the words from A as a prefix?

I was hoping to be able to do this from the command line maybe using grep but any other command line solution would be great too.

For example, if A is

apple
bob
cheese

and B is

aple
bob123
ches

I would like the line bob123 to be returned.

Solution

One approach uses bash's process substitution and sed to add a regular expression beginning-of-line ^ anchor to each line of A, and then tells grep to use it as a list of regular expressions to search for:

$ grep -f <(sed 's/^/^/' a.txt) b.txt
bob123

Answered By - Shawn

Answer Checked By - Timothy Miller (WPSolving Admin)