linux cat

usage : cat [option] file

redirection
> (n)   //  n is file or hardware output
< (n)  // n is file or hardware input
>> (n) // n is add tail

output : > , >>
input : < , <<

(1) cat > fun.txt    // create
(2) cat >> fun.txt    // add
(3) cat fun.txt // read
(4) cat -n fun.txt | more  // add line number and line by line output in fun.txt
(5) cat /etc/lilo.conf | grep linux   // "linux" which is included lilo.conf output
(6) cat /etc/lilo.conf | grep -v linux // linux form inside file was not included output