How can I make ack search through a list of files listed in a text file?

Question

I have foo.txt that contains a list of file names, delimited by newline. What I want to do is to use ack to search through the files listed in the foo.txt. How can I do that?

Answer 1

xargs -0 -n 1 grep search-string < foo.txt 

# -0 to handle filenames with spaces
# -n 1 means process a single file at a time