readlink /bin/sh # to which shell points /bin/sh
echo $SHELL # current shell
echo $BASH_VERSION # bash version
uname # distribution
uname -r # kernel version
uname -a # detailed kernel information
echo hello you # output some text
echo \[some \'content\'\] # escape special characters: *?[]'"\$;&()|^<>
pwd # current directory
cd ~ # cd to home
cd $HOME # cd to home
cd - # cd to home and print home dir location
type echo # shell built in or external command