cat(1) -n Evidencias%2FBulk_PC-20170427_%2Furl.txt %7C egrep -Eo %22%28http%7Chttps%7Cwww%29%3A%2F%2F%5Ba-zA-Z0-9.%2F%25%26%3F%3D_-%5D*%22 %7C sort %7C uniq %7C egrep -i %22xxx%7Cporn%7Cphoto%7Cvideo%7Cjpg%7Cjpeg%22 %7C head
concatenate files and print on the standard output
-n, --number
       number all output lines
Concatenate FILE(s), or standard input, to standard output.

With no FILE, or when FILE is -, read standard input.
-E, --show-ends
       display $ at end of each line
source manpages: cat