Linux Commands - Part 4

whoami  - This is used get who is the current user.
hostname – This is used to get name of the machine.
who          -Show who is logged into the system.
Date         - Show the current date and time
printenv - Print vales o fall environment variables.
env            -Print current environment.

su -This command is used to change the shell user.

  su -            {change  the shell to the super user / root}
  su - root   {change  the shell to the super user / root}
  su - Saman       {change  the shell to the super Saman}

id - This is used to print user's  information

 id                     {show current user information}
 id Saman         {show user Saman information}

uname - This used to get machine and operating system information

 uname              {show operating system}
 uname -a          {show all info, OS, Kernel version, architecture}
 uname  -r         {show kernel version}

groups  - This used to get user belongs group informations

 groups                         { groups of current user}
 groups  Saman             {groups of user Saman}         

 cat  - This is used to show file content

 cat /etc/passwd       {show /etc/passwd file content }

head - This used to show first n lines of a file

 head -10 /etc/passwd  
 {show first 10 lines of the file passwd in /etc }        

tail - This used to show last n lines of a file

 tail -10 /etc/passwd  
 {show last 10 lines of the file passwd in /etc }         

wc - This used to get count {word,line,charactor}

 wc       /etc/passwd 
{show line,word,charactor count of the file passwd}
 wc -l   /etc/passwd 
{show line count of passwd file in /etc folder}
 wc -c   /etc/passwd     
{show characor count of passwd file in /etc folder}
 wc -w   /etc/passwd   
{show word count of passwd file in /etc folder}

ps - This used to get active proccess

  ps                     {show active processes}
  ps aux              {show every all peocesses}

kill - This used to kill (destroy) a process

 kill 1960          {kill a process has id 1960  }