Some Basic Unix Command:
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Help:-
	man <command>	: give manual page (help) for the command
	man -k <keyword>: list commands with the keyword

Directory:-
	ls	  : list the directory
	ls -l	  : a long listing of the directory
	mkdir	  : make a new directory
	rmdir	  : remove (delete) a directory
	cd 	  : change directory (move) to home directory
	cd ..	  : move up one directory
	cd <path> : move to the path directory
	pushd	  : go back to the last directory
	pwd	  : list the path of the directory
	mv <oldname> <newname>	: rename file or directory

File:-
	more <filename>	 : list the file content
	cat <filename>	 : type the file content
	emacs <filename> : edit the file using emacs
	vi <filename>	 : edit the file using vi
	rm <filename>	 : remove (delete) a file
	grep <string> <filename> : match the string in the file & list them
	mv <oldname> <newname>	 : rename file or directory

Printing:-
	lpr <filename>	: print the file
	lpq 		: list the queue on the printer jobs
	lprm <job no.>	: delete the job from the queue
	enscript	: convert file to postscript format for printing
		e.g. enscript -G <filename>
		     enscript -G -2r <filename>

Process control:-
	ps	   : list the processes and and their status
	kill <PID> : kill the process with process id <PID>
		e.g. kill -9 <PID>  it is a sure kill

Mail:-
	mail	: list the mail in the mail box
		<no.>	: type the content of message no. <no.>
	   	?	: list the commands in the mail tool
	   	x	: exit without any changes
		check others command with ?

Others:-
	alias	: list the aliases of commands
	alias <your command> <system command>:
		substitute your command with the system command.
	who 	: who login in the system
	from	: display sender & date of newly arrived mail messages