In Bash, how to add “Are you sure [Y/n]” to any co

问题:

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://[e-mail]//somepath/morepath, which is actually an alias. Is there a standard command that can be added to the alias to achieve it?

The reason is that hg push and hg out can sound similar and sometimes when I want hgoutrepo, I may accidentlly type hgpushrepo (both are aliases).

Update: if it can be something like a built-in command with another command, such as: confirm && hg push ssh://... that'd be great... just a command that can ask for a yes or no and continue with the rest if yes.

回答1:

These are more compact and versatile forms of Hamish's answer. They handle any mixture of upper and lower case letters:

read -r -p "Are you sure? [y/N] " response
case "$response" in
    [yY][eE][sS]|[yY]) 
        do_something
        ;;
    *)
        do_something_else
        ;;
esac

Or, for Bash >= version 3.2:

read -r -p "Are you sure? [y/N] " response
if [[ "$response" =~ ^([yY][eE][sS]|[yY])+$ ]]
then
    do_something
else
    do_something_else
fi

Note: If $response is an empty string, it will give an error. To fix, simply add quotation marks: "$response". – Always use double quotes in variables containing strings (e.g.: prefer to use "$@" instead $@).

Or, Bash 4.x:

read -r -p "Are you sure? [y/N] " response
response=${response,,}    # tolower
if [[ "$response" =~ ^(yes|y)$ ]]
...

Edit:

In response to your edit, here's how you'd create and use a confirm command based on the first version in my answer (it would work similarly with the other two):

confirm() {
    # call with a prompt string or use a default
    read -r -p "${1:-Are you sure? [y/N]} " response
    case "$response" in
        [yY][eE][sS]|[yY]) 
            true
            ;;
        *)
            false
            ;;
    esac
}

To use this function:

confirm && hg push ssh://..

or

confirm "Would you really like to do a push?" && hg push ssh://..

回答2:

Here is roughly a snippet that you want. Let me find out how to forward the arguments.

read -p "Are you sure you want to continue? <y/N> " prompt
if [[ $prompt == "y" || $prompt == "Y" || $prompt == "yes" || $prompt == "Yes" ]]
then
  # http://stackoverflow.com/questions/1537673/how-do-i-forward-parameters-to-other-command-in-bash-script
else
  exit 0
fi

Watch out for yes | command name here :)

回答3:

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.

回答4:

Confirmations are easily bypassed with carriage returns, and I find it useful to continually prompt for valid input.

Here's a function to make this easy. "invalid input" appears in red if Y|N is not received, and the user is prompted again.

prompt_confirm() {
  while true; do
    read -r -n 1 -p "${1:-Continue?} [y/n]: " REPLY
    case $REPLY in
      [yY]) echo ; return 0 ;;
      [nN]) echo ; return 1 ;;
      *) printf " \033[31m %s \n\033[0m" "invalid input"
    esac 
  done  
}

# example usage
prompt_confirm "Overwrite File?" || exit 0

You can change the default prompt by passing an argument

回答5:

This may be a hack:

as in question In Unix / Bash, is "xargs -p" a good way to prompt for confirmation before running any command?

we can using xargs to do the job:

echo ssh://[e-mail]//somepath/morepath | xargs -p hg push

of course, this will be set as an alias, like hgpushrepo

Example:

$ echo foo | xargs -p ls -l
ls -l foo?...y
-rw-r--r--  1 mikelee    staff  0 Nov 23 10:38 foo

$ echo foo | xargs -p ls -l
ls -l foo?...n

$

回答6:

Add the following to your /etc/bashrc file. This script adds a resident "function" instead of an alias called "confirm".

---

function confirm( )
{
#alert the user what they are about to do.
echo "About to $@....";
#confirm with the user
read -r -p "Are you sure? [Y/n]" response
case "$response" in
    [yY][eE][sS]|[yY]) 
              #if yes, then execute the passed parameters
               "$@"
               ;;
    *)
              #Otherwise exit...
              echo "ciao..."
              exit
              ;;
esac
}

回答7:

read -r -p "Are you sure? [Y/n]" response
  response=${response,,} # tolower
  if [[ $response =~ ^(yes|y| ) ]] || [[ -z $response ]]; then
      your-action-here
  fi

回答8:

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.

回答9:

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

回答10:

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"

回答11:

No pressing enter required

Here's a longer, but reusable and modular approach:

• Returns 0=yes and 1=no
• No pressing enter required - just a single character
• Can press enter to accept the default choice
• Can disable default choice to force a selection
• Works for both zsh and bash.

Defaulting to "no" when pressing enter

Note that the N is capitalsed. Here enter is pressed, accepting the default:

$ confirm "Show dangerous command" && echo "rm *"
Show dangerous command [y/N]?

Also note, that [y/N]? was automatically appended. The default "no" is accepted, so nothing is echoed.

Re-prompt until a valid response is given:

$ confirm "Show dangerous command" && echo "rm *"
Show dangerous command [y/N]? X
Show dangerous command [y/N]? y
rm *

Defaulting to "yes" when pressing enter

Note that the Y is capitalised:

$ confirm_yes "Show dangerous command" && echo "rm *"
Show dangerous command [Y/n]?
rm *

Above, I just pressed enter, so the command ran.

No default on enter - require y or n

$ get_yes_keypress "Here you cannot press enter. Do you like this"
Here you cannot press enter. Do you like this [y/n]? k
Here you cannot press enter. Do you like this [y/n]?
Here you cannot press enter. Do you like this [y/n]? n
$ echo $?
1

Here, 1 or false was returned. Note no capitalisation in [y/n]?

Code

# Read a single char from /dev/tty, prompting with "$*"
# Note: pressing enter will return a null string. Perhaps a version terminated with X and then remove it in caller?
# See https://unix.stackexchange.com/a/367880/143394 for dealing with multi-byte, etc.
function get_keypress {
  local REPLY IFS=
  >/dev/tty printf '%s' "$*"
  [[ $ZSH_VERSION ]] && read -rk1  # Use -u0 to read from STDIN
  # See https://unix.stackexchange.com/q/383197/143394 regarding '\n' -> ''
  [[ $BASH_VERSION ]] && </dev/tty read -rn1
  printf '%s' "$REPLY"
}

# Get a y/n from the user, return yes=0, no=1 enter=$2
# Prompt using $1.
# If set, return $2 on pressing enter, useful for cancel or defualting
function get_yes_keypress {
  local prompt="${1:-Are you sure} [y/n]? "
  local enter_return=$2
  local REPLY
  # [[ ! $prompt ]] && prompt="[y/n]? "
  while REPLY=$(get_keypress "$prompt"); do
    [[ $REPLY ]] && printf '\n' # $REPLY blank if user presses enter
    case "$REPLY" in
      Y|y)  return 0;;
      N|n)  return 1;;
      '')   [[ $enter_return ]] && return "$enter_return"
    esac
  done
}

# Credit: http://unix.stackexchange.com/a/14444/143394
# Prompt to confirm, defaulting to NO on <enter>
# Usage: confirm "Dangerous. Are you sure?" && rm *
function confirm {
  local prompt="${*:-Are you sure} [y/N]? "
  get_yes_keypress "$prompt" 1
}    

# Prompt to confirm, defaulting to YES on <enter>
function confirm_yes {
  local prompt="${*:-Are you sure} [Y/n]? "
  get_yes_keypress "$prompt" 0
}

回答12:

This isn't exactly an "asking for yes or no" but just a hack: alias the hg push ... not to hgpushrepo but to hgpushrepoconfirmedpush and by the time I can spell out the whole thing, the left brain has made a logical choice.

回答13:

Not the same, but idea that works anyway.

#!/bin/bash  
i='y'  
while [ ${i:0:1} != n ]  
do  
    # Command(s)  
    read -p " Again? Y/n " i  
    [[ ${#i} -eq 0 ]] && i='y'  
done  

Output:
Again? Y/n N
Again? Y/n Anything
Again? Y/n 7
Again? Y/n &
Again? Y/n nsijf
$

Now only checks 1st character of $i read.

回答14:

Below code is combining two things

1. shopt -s nocasematch that will take care of case insensitive

2. and if condition that will accept both the input either you pass yes,Yes,YES,y.

   shopt -s nocasematch

   if [[ sed-4.2.2.$LINE =~ (yes|y)$ ]]

   then exit 0

   fi

回答15:

Here is my solution that using localised regex. So in german also "j" for "Ja" would be interpreted as yes.

First argument is the question, if the second argument is "y" than yes would be the default answer otherwise no would be the default answer. The return value is 0 if the answer was "yes" and 1 if the answer was "no".

function shure(){
    if [ $# -gt 1 ] && [[ "$2" =~ ^[yY]*$ ]] ; then
        arg="[Y/n]"
        reg=$(locale noexpr)
        default=(0 1)
    else
        arg="[y/N]"
        reg=$(locale yesexpr)
        default=(1 0)
    fi
    read -p "$1 ${arg}? : " answer
    [[ "$answer" =~ $reg ]] && return ${default[1]} || return ${default[0]}
}

Here is a basic usage

# basic example default is no
shure "question message" && echo "answer yes" || echo "answer no"
# print "question message [y/N]? : "

# basic example default set to yes
shure "question message" y && echo "answer yes" || echo "answer no"
# print "question message [Y/n]? : "

回答16:

This may be a little too short, but for my own private use, it works great

read -n 1 -p "Push master upstream? [Y/n] " reply; 
if [ "$reply" != "" ]; then echo; fi
if [ "$reply" != "n" ]; then
    git push upstream master
fi

The read -n 1 just reads one character. If it's not a lowercase 'n', it is assumed to be a 'Y'.

(as for the real question: make that a bash script and change your alias to point to that script instead of what is was pointing to before)