Preventing script from going back to main menu upon invalid input

lgu · 07-13-2013, 01:41 PM

Scripting beginner here, I'm trying to get the code below to automatically re-prompt for the username and password again if the user enters a blank field or if the username already exists. Right now, it's simply asking the user if they want to rerun the script again from the main menu (which I want it to continue to do if the creation of the account is successful).

Quote:

RUNSCRIPT="YES" # Allows script to run until user enters "N" for "No."
while [[ $RUNSCRIPT = "YES" ]]
do

echo "1. Create User and Password" # Main Menu options
echo "2. Reset User Password"
echo "3. Password Management"
echo "4. Create Group"
echo "5. List Users"
echo "6. Search for User"
echo "7. View User's Activity"
echo "8. Lock User"
echo "9. Unlock User"
echo "10. Delete User"
echo "11. Delete Group"
echo "12. Quit"
read -p "Select a number option from the choices above: " choice # Reads the user's numerical choice
case "$choice" in
1) read -p "Enter new username: " username
read -s -p "Enter new password: " password
if [ "$username" == "" -o "$password" == "" ]
then
echo ""
echo "Field(s) blank!"
else

egrep "^$username:" /etc/passwd >/dev/null

if [ $? -eq 0 ]; then # Checks to see if username already exists.
echo ""
echo "$username exists!"
else
read -p "Do you want this user's password to be encrypted? (Y or N) " YesNo
fi
fi

YN=`echo $YesNo | tr [:lower:] [:upper:]`
case $YN in
Y) useradd -m -p `openssl passwd -1 -salt 9Qj/F.Xw $password` $username # Creates a new username and an encrypted password
echo "New user $username created with encrypted password!"
;;
N) useradd -m -p $password $username # Creates a new username and a plain-text password
echo "New user $username created!"
;;

*) echo "Invalid choice, please try again." ;;
esac ;;
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
*) echo "That is not a valid choice. Try a number from 1 to 12." ;;
esac
read -p "Select another option? (Yes/No) " YesNo # Asks the user if they want to go back to main menu
RUNSCRIPT=` echo $YesNo | tr [:lower:] [:upper:]`
clear
done

unSpawn · 07-13-2013, 02:20 PM

Quote:

Originally Posted by lgu

I'm trying to get the code below to automatically re-prompt for the username and password again if the user enters a blank field or if the username already exists.

Code:

_userPass() { # I prefer using functions. Example:
read -p "Enter new username: " _INPUT_USER
read -s -p "Enter new password: " _INPUT_PASSWD
[ ${#_INPUT_USER} -eq 0 -o "${_INPUT_PASSWD} ] && { echo "User name or password field left blank: retry.";_userPass ; }
getent "${_INPUT_USER}" passwd >/dev/null 2>&1 || { echo "User name error: retry.";_userPass ; }
useradd -m "${_INPUT_USER}" || { echo "User name creation failure, exiting.";exit 1 ; }
openssl passwd -salt $(openssl rand -base64 6) -noverify :${_INPUT_PASSWD}"|passwd --stdin "${_INPUT_USER}"
}

# You see it calls itself if necessary. Now just call the function inside your script:
_userPass
# and there you go.

lgu · 07-13-2013, 03:46 PM

Thanks so much, never thought to make it a function. Works great and it's a lot cleaner.

devnull10 · 07-15-2013, 04:25 AM

Just for reference, an alternate way would be to do something like:

Code:

while input is not valid
  prompt for input
loop

konsolebox · 07-16-2013, 07:21 PM

You could make use of continue and break within that loop.
See

Code:

help continue; help break

David the H. · 07-19-2013, 05:43 AM

Please use ***[code][/code]*** tags around your code and data, to preserve the original formatting and to improve readability. Do not use quote tags, bolding, colors, "start/end" lines, or other creative techniques. Thanks.

I think you should break this up into multiple parts. Start with the main menu, then have it call individual functions for doing the sub-actions. That way you can run the function menus in loops of their own until you get the input you want, and exit back to the main menu when done.

It also helps to keep clutter down and make your script more readable and debuggable. ( See Scripting With Style )

And yes, it's usually best to just use a simple while true loop, test the input, and issue continue or break commands to control whether to loop through it again.

Simplified example:

Code:

#It's better to process name and password separately

usertest(){

    local username

    while true; do

        read -p "Enter new username: " -r username

        case $username in
            '')
                echo "username blank!  Try again."
                continue
            ;;
            *[^a-z0-9]*)
                echo "username contains invalid characters!  Try again."
                continue
            ;;
            *)
               echo "username ok"
               break
            ;;
        esac

    done
      
passtest(){

    local password
    
    while true; do

        read -p "Enter new password: " -r password

    ......etc .....

}


#run the main menu

while true; do

    read -p "Select a number option from the choices above:" -r choice

    case "$choice" in

        1)
           usertest
           passtest
        ;;

        .....etc......

    esac

done

And a couple more scripting hints for you:

Code:

if [ "$username" == "" -o "$password" == "" ]; then

if [ $? -eq 0 ]

When using advanced shells like bash or ksh, it's recommended to use [[..]] for string/file tests, and ((..)) for numerical tests. Avoid using the old [..] test unless you specifically need POSIX-style portability.

http://mywiki.wooledge.org/BashFAQ/031
http://mywiki.wooledge.org/ArithmeticExpression

Code:

#YN=`echo $YesNo | tr [:lower:] [:upper:]`

This is also unneeded in shells like bash or ksh that have advanced parameter substitution patterns built in:

Code:

YN=${YesNo^^}

Also, $(..) is highly recommended over `..`.