The shell (=command line) is a program that takes keyboard commands and passes them to the operating system.
Terminal emulator program for interacting with the shell (Command line, Terminal,…).
Shell prompt is the beginning of the line in the terminal emulator, e.g. [me@linuxbox ~]$. If the last character of the prompt is a pound sign (“#”) rather than a dollar sign, the terminal session has superuser privileges.
Filenames and commands in Linux, like Unix, are case sensitive.

Simple commands

cal – calendar
df – disk free space
free – free memory
exit – exit terminal session


~ = user’s home dir
pwd – print current dir path
cd – change dir (cd someDir, cd .., cd ., cd – (previous working directory), cd ~user_name (home dir of user))
ls – list files in dir (-a (hidden files), -l (long format))
examples: list two dirs: ls ~ /usr
cp – copy files/dirs (cp -u *.html destination)
mv – move/rename files/dirs
mkdir – create dirs
rm – remove files/dirs
ln – create hard/symbolic links

Options and arguments
ls -lt –reverse – see ls page

Exploring The System

file – displays file type (short desc of files content)
less (improved replacement for more)- read file (up=b, down=space, scroll by one line=arrow up/down, go to the end/beginning of the file=G/g, search=/string, quit=q )

Manipulating files and dirs