Prepend every line in a file with some text

Say you have a file 'files.txt' looking like this:
p1-c-b-1.fastq.gz
p1-c-b-2.fastq.gz
p1-c-c-1.fastq.gz

Now, you would like to add a full URL path to each of those lines, prepending existing text.
Use awk as follows:
$ cat files.txt | awk '{ print "http://www.complete.url.com/", $0; }' > links.txt

You get a file names 'links.txt' looking like this:
http://www.complete.url.com/ p1-c-b-1.fastq.gz
http://www.complete.url.com/ p1-c-b-2.fastq.gz
http://www.complete.url.com/ p1-c-c-1.fastq.gz


To get rid of introduced extra white space, use sed:
$ cat links.txt | sed 's/ //g'