`cat` tool is used to concatenate files and print it on standard output. This tool is used to see text of file.
cat [options] [filename]
[ -n ] :It does numbering of each line.
[ -b ] :It numbers only non empty lines.
[ -E ] :It outputs $ at end of each line.
cat tool can also used to concat text to file. It uses input operator for passing data and uses [ ctl + d ] to escape.