blackzphoenix

    #!/bin/bash
    read -s -p "Enter your password :  " pass
    echo 
    #checks whether the string is non zero
    if test -z $pass 
    then
        echo "No password was entered!!! Cannot verify an empty password!!!"
        exit 1
    elif test "$pass" != "gnu"
    then

blackzphoenix

    #Numerical Comparison
    eq 	INTEGER1 -eq INTEGER2 	INTEGER1 is equal to INTEGER2 
    ge 	INTEGER1 -ge INTEGER2 	INTEGER1 is greater than or equal to INTEGER2 
    gt 	INTEGER1 -gt INTEGER2 	INTEGER1 is greater than INTEGER2 
    le 	INTEGER1 -le INTEGER2 	INTEGER1 is less than or equal to INTEGER2
    lt 	INTEGER1 -lt INTEGER2 	INTEGER1 is less than INTEGER2 
    ne 	INTEGER1 -ne INTEGER2 	INTEGER1 is not equal to INTEGER2 

blackzphoenix

    #!/bin/bash
    [ ! -d shell ] && mkdir shell
    [ ! -f prog1.sh ] && touch prog1.sh

blackzphoenix

    ! expression    [ ! expression ]    if test ! condition    if [ ! condition ]
                                        then                   then
                                          command1               command1
                                          ...                    ...
                                          commandN               commandN 
                                        fi                     fi

blackzphoenix

    #!/bin/bash
    FILE=/etc/passwd

    read -p "Enter a user name : " username

    #locate the username in the file passwd
    if grep "^$username:" /etc/passwd >/dev/null
    then
	echo "User '$username' found in $FILE file."
    else

blackzphoenix

           if condition
           then
                       condition is true
                       execute all commands up to elif statement
           elif condition1 
           then
                       condition1 is true
                       execute all commands up to elif statement  
           elif condition2
           then

blackzphoenix

	if condition
	then
		if condition
		then
			command1
			.....
			..
			commandN
		else
			command1

blackzphoenix

    #!/bin/bash
    read -p "Enter a number : " num
    if test $num -ge 0
    then
    	echo "$num is Positive number."
    else
	echo "$num number is Negative number."
    fi

blackzphoenix

if condition       if test var -eq val    
then               then                    
  command1           command1                 
  command2           command2                
  ...                ...                   
  commandN           commandN                 
else               else                    
  command1           command1                
  command2           command2               
  ...                ...                    

blackzphoenix

#!/bin/bash
read -p "Enter a Password : " pass
if test "$pass" == "gnu"
then
     echo "Password verified."
fi