How to select and output URL addresses out of any file?

Question

I would like to know what command would:

1. select all URL in a file (i.e. recognize all addresses beginning with http or www from the beginning to the end and separate them from text or other data)

2. output them in a .txt file.

The idea is to perform next a wget -i on the .txt file. I need to properly select and output these URL in a .txt file as wget struggles to directly identify all URL in the raw file.

Answer 1

I followed instructions in How to use grep and cut in script to obtain website URLs from an HTML file and it worked perfectly in my case, as URL are between < href > in the input file:

grep -Po '(?<=href=")[^"]*(?=")' INPUT_FILE > OUTPUT_FILE.txt