In Bash, how to add “Are you sure [Y/n]” to any command or alias?

Question

In this particular case, I\'d like to add a confirm in Bash for

Are you sure? [Y/n]

for Mercurial\'s hg push ssh://username@www.example.com//some

Answer 1

This version allows you to have more than one case y or Y, n or N

1. Optionally: Repeat the question until an approve question is provided

2. Optionally: Ignore any other answer

3. Optionally: Exit the terminal if you want

   confirm() {
       echo -n "Continue? y or n? "
       read REPLY
       case $REPLY in
       [Yy]) echo 'yup y' ;; # you can change what you do here for instance
       [Nn]) break ;;        # exit case statement gracefully
       # Here are a few optional options to choose between
       # Any other answer:
   
       # 1. Repeat the question
       *) confirm ;;
   
       # 2. ignore
       # *) ;;
   
       # 3. Exit terminal
       # *) exit ;;
   
       esac
       # REPLY=''
   }
   

Notice this too: On the last line of this function clear the REPLY variable. Otherwise if you echo $REPLY you will see it is still set until you open or close your terminal or set it again.

Answer 2

Well, here's my version of confirm, modified from James' one:

function confirm() {
  local response msg="${1:-Are you sure} (y/[n])? "; shift
  read -r $* -p "$msg" response || echo
  case "$response" in
  [yY][eE][sS]|[yY]) return 0 ;;
  *) return 1 ;;
  esac
}

These changes are:

1. use local to prevent variable names from colliding
2. read use $2 $3 ... to control its action, so you may use -n and -t
3. if read exits unsuccessfully, echo a line feed for beauty
4. my Git on Windows only has bash-3.1 and has no true or false, so use return instead. Of course, this is also compatible with bash-4.4 (the current one in Git for Windows).
5. use IPython-style "(y/[n])" to clearly indicate that "n" is the default.

Answer 3

Late to the game, but I created yet another variant of the confirm functions of previous answers:

confirm ()
{
    read -r -p "$(echo $@) ? [y/N] " YESNO

    if [ "$YESNO" != "y" ]; then
        echo >&2 "Aborting"
        exit 1
    fi

    CMD="$1"
    shift

    while [ -n "$1" ]; do
        echo -en "$1\0"
        shift
    done | xargs -0 "$CMD" || exit $?
}

To use it:

confirm your_command

Features:

• prints your command as part of the prompt
• passes arguments through using the NULL delimiter
• preserves your command's exit state

Bugs:

• echo -en works with bash but might fail in your shell
• might fail if arguments interfere with echo or xargs
• a zillion other bugs because shell scripting is hard

Answer 4

To avoid explicitly checking for these variants of 'yes' you could use the bash regular expression operator '=~' with a regular expression:

read -p "Are you sure you want to continue? <y/N> " prompt
if [[ $prompt =~ [yY](es)* ]]
then
(etc...)

That tests whether the user input starts with 'y' or 'Y' and is followed by zero or more 'es's.

Answer 5

Try,

 #!/bin/bash
 pause ()
 {
 REPLY=Y
 while [ "$REPLY" == "Y" ] || [ "$REPLY" != "y" ]
 do
  echo -e "\t\tPress 'y' to continue\t\t\tPress 'n' to quit"
  read -n1 -s
      case "$REPLY" in
      "n")  exit                      ;;
      "N")  echo "case sensitive!!"   ;; 
      "y")  clear                     ;;
      "Y")  echo "case sensitive!!"   ;;
      * )  echo "$REPLY is Invalid Option"     ;;
 esac
 done
 }
 pause
 echo "Hi"