Use a opção -i
:
wget -i ./url.txt
De man wget
:
-i file
--input-file=file
Read URLs from a local or external file. If - is specified as file, URLs are read from the standard input. (Use ./- to read from a file literally named -.) If this function is used, no URLs need be present on the command line. If there are URLs both on the command line and in an input file, those on the command lines will be the first ones to be retrieved. If --force-html is not specified, then file should consist of a series of URLs, one per line.
However, if you specify --force-html, the document will be regarded as html. In that case you may have problems with relative links, which you can solve either by adding "" to the documents or by specifying --base=url on the command line.
If the file is an external one, the document will be automatically treated as html if the Content-Type matches text/html. Furthermore, the file's location will be implicitly used as base href if none was specified.