xargs -n 1 ./script.sh <list.txt
In this example, xargs will execute ./script.sh multiple times with a single argument read from its standard input.
The standard input comes from the file list.txt via a simple shell input redirection. This assumes that the list.txt file contains one argument to use with the script per line.
The ./script.sh script will be executed once for each line in the list.txt file.
About the -n flag to xargs
-n numberInvoke utility using as many standard input arguments as possible, up to
number(a positive decimal integer) arguments maximum.
Another solution would be to allow the script to read directly from list.txt, or to take multiple command line argument (the entries from list.txt), and to download the files in one or several batches. But since we don't know what the mechanics of the script is, I can't make any detailed explanation of how to go about doing this.