Linux Shell and Commands
echo $variable
BASH, SHELL, CPU, DISPLAY, ENV, EUID, HISTFILE HISTSIZE, HOME, HOST, LOGNAME, MAIL, MANPATH OLDPWD, OSTYPE, PATH, PSI, PWD
who am i
Displays the username of the current logged on user
Three options to view environmental variables
Echo, set, env command
netstat
Gives you network connection-related status information
top
Lists applications and processes currently running on the system including resource consumption
env
Show the environment variables for the current logged on user account
st derr
Standard error; error code generated by a command if an error occurs
st din
Standard input; input provided for a command to process
st dout
Standard output; the output from a particular command
ifconfig
Used to list information about your network interface card
route
Used to view and alter the local route table of the system
which
Used to view the location of where a command or utility is kept
Gnome Display Manager
a program that manages graphical displays servers and handles graphical user logins
su
allows you to switch to a different user account while in the shell prompt
man short for Manual
are files and used for a particular command /usr/share/man folder is the man file folder
Environmental Variables
area of RAM that is reserved to store information that defines a specific value in your OS user environment
info if config
bring up the info page for if config command
man if config
bring up the man page for the if config command
Shell
command interpreter that allows users to type commands that are then sent to the OS kernel to be executed
uname
depending on the switch, the command gives multiple information-related stats about the system
-v
display Linux version number
-a
display all information
-m
display hardware architecture
-i
display hardware platform
-n
display host name
-s
display kernel name
-r
display kernel release number
-o
display operating system
-p
display processor type
Bourne Shell (sh)
earliest shell; still used frequently on UNIX systems
tcsh
improved version of csh that added new features; default shell on FreeBSD systems
Z Shell (zsh)
improved version of sh that includes features from bash, tcsh and Korn shell (ksh)
Borne-Again Shell (bash)
improved version of sh; used by default on most Linux systems
ls command and dir command
list the files and directories in a directory
Reboot
only be performed by root user and will restart the system
init 6
only be performed by root user and will restart the system
Halt
only be performed by root user and will turn off the system
init 0
only be performed by root user and will turn off the system
shutdown
only be used by the root to shutdown or reboot the system
CTRL-ALT-X
open multiple shell sessions (Fx= F1-F6) and F7 will revert to GUI session
C Shell (csh)
originally developed for BSD UNIX; syntax is very similar to C programming
Echo $Shell
see what shell you are using
Alias
shortcut to a longer command snytax, system boots alias goodbye=shutdown -h now
Redirection and Piping
two ways to manipulate input and output of commands in the Linux Shell
Switch to Z Shell
type zsh and original shell type exit
Change sessions/terminal windows
use export command, original var=val syntax SHELL=/bin/sh and export SHELL
2 ways to get help with Linux commands
use man pages and Info
Login Shell
used in text-based CLI environments, CLI shells contains multiple config files that make up a user environment
Echo Command
used to print text to the screen
echo
used to repeat back whatever you type or to display environment-related information
Non-Login Shell
used when opening a terminal window in a GUI environment
Set value of a variable
variable= value and export command
