cat(1) -n %2Fhome%2Fmarcos%2FEvidencias%2FBulk_PC-20170427_%2Femail.txt %7C egrep -o %22%5Cb%5Ba-zA-Z0-9.-%5D%2B%40%5Ba-zA-Z0-9.-%5D%2B%5C.%5Ba-zA-Z0-9.-%5D%2B%5Cb%22 %7C sort %7C uniq %7C egrep -i %22gmail%7Chotmail%7Cproton%7Cfacebook%22 
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.
source manpages: cat