cat - less - more
cat loads the whole file, fit well with reading small config file
less is suggested for reading log, large file, less is more
g - go to top
G - go to bottom
/keyword - search for keyword
b - go backward 1 page
f - go forward 1 page
q - quit
common usage of cat:
cat a b > c: concatenate content of a and b and redirect the output to file c
cat > foo.txt: read from stdin and redirect to foo.txt