An address book written in shell scripts

For example, the following is an address book written in a Linux Shell script. The "add, delete, and query" function has been implemented. The "change" function is complex and is to be continued ~~

 1 #!/dev/bash 2  3 # Name of address book 4 BOOK="address-book.txt" 5  6 exit=0 7  8 add() { 9     # Ask the user for a name and assign to a variable10     echo -n "Name of person: " 11     read name12 13     # Ask the user for a phone number and assign to a variable14     echo -n "Phone number: "15     read phone16 17     # Echo the answers and ask for confirmation18     echo "Should I enter the values:"19     echo -e "$name ; $phone \n"20     echo -n "y/n: "21     read answer22 23     if [ "$answer" == "y" ] 24     then25     # Write the values to the address book26     echo "$name ; $phone" >>$BOOK27     else28     # Give the user a message29     echo "$name ; $phone NOT written to $BOOK"30     fi31 }32 33 34 list() {35     # Print the book with line numbers and paused with less36     nl --number-separator=":    " $BOOK | less 37 }38 39 find() {40     # Ask the user what to look for.41     echo -n "What person or number are you seeking: "42     read find43 44     # Print the header before the answer45     echo "Name ; Phone number"46     grep -i $find $BOOK47 }48 49 del() {50     # Ask the user which line to delete51     echo -n "Which line should I delete: "52     read number53 54     # Rename the file before deleting55     mv $BOOK boo.txt56 57     # Add line numbers and delete against that number58     nl --number-separator=":" boo.txt | grep -v $number: | awk -F: '{print $2}' |  tee $BOOK59 }60 61 62 main() {63     while [ $exit -ne 1 ]64     do65     echo "What operation do you want?"66     echo -e "add, list, find, del, exit: "67     read answer68 69     if [ "$answer" = "add" ]70     then71         add72     elif [ "$answer" = "list" ]73     then74         list75     elif [ "$answer" = "find" ]76     then77         find78     elif [ "$answer" = "del" ]79     then80         del81     elif [ "$answer" = "exit" ]82     then83         exit=184     else85         echo "I do not understand the command."86     fi87     done88     exit 089 }90 main