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//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.
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://..
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" || $prompt == "Yes" ]]
then
# http://stackoverflow.com/questions/1537673/how-do-i-forward-parameters-to-other-command-in-bash-script
else
exit 0
fi
Watch out for yes | command name here :)
Confirmations are easily bypassed with carriage returns, and I find it useful to continually prompt for valid input.
Here's a function to make this easy. "invalid input" appears in red if Y|N is not received, and the user is prompted again.
prompt_confirm() {
while true; do
read -r -n 1 -p "${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
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.
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://username#www.example.com//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
$
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" = "${reply#[Nn]}" ]; then
git push upstream master
fi
The read -n 1 just reads one character. No need to hit enter. If it's not a 'n' or 'N', it is assumed to be a 'Y'. Just pressing enter means Y too.
(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)
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
"$#"
;;
*)
#Otherwise exit...
echo "ciao..."
exit
;;
esac
}
read -r -p "Are you sure? [Y/n]" response
response=${response,,} # tolower
if [[ $response =~ ^(yes|y| ) ]] || [[ -z $response ]]; then
your-action-here
fi
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
}
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:
use local to prevent variable names from colliding
read use $2 $3 ... to control its action, so you may use -n and -t
if read exits unsuccessfully, echo a line feed for beauty
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).
use IPython-style "(y/[n])" to clearly indicate that "n" is the default.
This version allows you to have more than one case y or Y, n or N
Optionally: Repeat the question until an approve question is provided
Optionally: Ignore any other answer
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 $REPLY you will see it is still set until you open or close your terminal or set it again.
Late to the game, but I created yet another variant of the confirm functions of previous answers:
confirm ()
{
read -r -p "$(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 $?
}
To use it:
confirm your_command
Features:
prints your command as part of the prompt
passes arguments through using the NULL delimiter
preserves your command's exit state
Bugs:
echo -en works with bash but might fail in your shell
might fail if arguments interfere with echo or xargs
a zillion other bugs because shell scripting is hard
Try,
#!/bin/bash
pause ()
{
REPLY=Y
while [ "$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"
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.
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 $i read.
Below code is combining two things
shopt -s nocasematch that will take care of case insensitive
and if condition that will accept both the input either you pass yes,Yes,YES,y.
shopt -s nocasematch
if [[ sed-4.2.2.$LINE =~ (yes|y)$ ]]
then exit 0
fi
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]? : "
I know this is an old question but this might help someone, it hasn't been addressed here.
I have been asked how to use rm -i in a script which is receiving input from a file. As file input to a script is normally received from STDIN we need to change it, so that only the response to the rm command is received from STDIN. Here's the solution:
#!/bin/bash
while read -u 3 line
do
echo -n "Remove file $line?"
read -u 1 -n 1 key
[[ $key = "y" ]] && rm "$line"
echo
done 3<filelist
If ANY key other than the "y" key (lower case only) is pressed, the file will not be deleted. It is not necessary to press return after the key (hence the echo command to send a new line to the display).
Note that the POSIX bash "read" command does not support the -u switch so a workaround would need to be sought.
Yes default base on Dennis Williamson answer
#!/bin/bash
confirm() {
# call with a prompt string or use a default
read -r -p "${1:-Are you sure?} [Y/n] " response
case "$response" in
#([nN])*([oO]))
false
;;
*)
true
;;
esac
}
I like to exit as soon as possible if the user isn't sure, and I like the code to be readable and short. Depending on whether you'd like the user to press Return after their answer or not,
With pressing Return,
read -p "Warning: something scary: Continue (Y/N)? " reply
[ $reply != 'Y' ] && [ $reply != 'y' ] && echo 'Aborting' && exit 1
echo 'Scary thing'
or if you prefer not to wait for the user to press Return,
read -n1 -p "Warning: something scary: Continue (Y/N)? " reply
echo ''
[ $reply != 'Y' ] && [ $reply != 'y' ] && echo 'Aborting' && exit 1
echo 'Scary thing'
The other answers have the background on that -n1 flag and other options for read. The echo '' in the 2nd variant is to make subsequent output appear on a new line since the user doesn't have to press Return, so no newline has been echoed to the terminal.
I am new to bash script. I want the user to input his choice, but the while-do loop does not terminate. I tired all choices of read [option] but some of them does not work. read -a stop the loop but does not accept the input. I am using windows machine and I am not sure if I need to install some other lib or packages.
I tried: read -p, read -a, read -r , read
function user_input {
while true; do
echo "1. choice 1"
echo "2. choice 2"
read -p "What choice would you like: [1,2] " ANS
case $ANS in
'1')
environment="-A"
break;;
'2')
environment="-B"
break;;
*)
echo "Wrong input, try again";;
esac
done
}
Because you have a case nested in a while, you should use break 2 to break both. Otherwise define a variable CON=true and set it to false in the case.
I have small script which have a function asking user input (name of user) and then I have echo function
which is running the function and asking for input,
After that I have echo the $User_name in last line (Users_name_is - )which is set in function but its result is black, I want to use $User_name in further script.
what i am doing wrong ?
#!/bin/sh
funtion_one()
{
read varname
if [ $varname == skull ]; then
echo "Nice to meet you $varname"
#User_name=$varname
else
echo "I dont know you $varname"
fi
User_name=$varname
}
echo Hello, who am I talking to?
while :
do
case $(funtion_one) in
"Nice to meet you skull") break
;;
"I dont know you") $(funtion_one)
;;
esac
done
echo "Users_name_is - $User_name"
I want result Users_name_is - skull
When you do $(funtion_one), you are executing the function inside a subshell, so any variables created cease to exist after the function finishes.
An alternative would be this:
function_one()
{
read varname
if [ "$varname" = skull ]; then
echo "Nice to meet you $varname" >&2
else
echo "I dont know you $varname" >&2
fi
echo "$varname"
}
user_name=$(function_one)
Now user_name exists in the parent shell. The messages are sent to standard error, and the name that has been read is sent to standard output so that it can be captured by the command substitution $().
Alternatively, you can simply execute the function in the parent shell:
# change
echo $(funtion_one)
# to
funtion_one
But then all the variables used inside the function will continue to exist after it has been run.
It seems the function is getting in the way of you achieving what you want. I would restructure your code to something much simpler like this:
while read name; do
if [ "$name" = skull ]; then
echo "Nice to meet you $name"
break
fi
echo "I don't know you $name"
done
There are a lot of ways to structure your code, and it seems like you're trying to do something like:
#!/bin/sh
get_user_name() {
local varname
printf 'Hello, who am I talking to? '
read varname
if test "$varname" = skull; then
echo "Nice to meet you $varname"
User_name=$varname
return 0
else
echo "I dont know you $varname" >&2
return 1
fi
}
unset User_name
while ! get_user_name
do
case "$User_name" in
skull) break
;;
esac
done
echo "Users_name_is - $User_name"
It's perfectly valid to use a function to get the input, but if you want that function to set a variable in the caller you cannot call it as a subshell, and it's easiest if the shell returns a value to indicate success or failure.
I'm making a bash script with a simple interactive menu that asks a yes or no question. I'm wondering if I can use a function to call itself and restart the prompt if the person writes random junk, is this possible?
Code:
Question () {
read -r -p "yes or no quesiotn [Y/N]"
Response
case Response in
Y|y)
#some code
;;
N|n)
#more code
;;
*)
ehco "im sorry i didnt catch that"
Question
;;
esac
}
Question
Instead of calling itself, make the function return appropriate exit codes, (a 1 for failed, a 0 for success), then have a do-nothing until loop do the work:
Question () {
read -r -p "Yes or no question [Y/N]?" Response
case "$Response" in
Y|y)
#some code
;;
N|n)
#more code
;;
*)
echo "I'm sorry I didn't catch that."
return 1
;;
esac
}
until Question ; do : ; done
While you can use recursion in this case, it's not recommended because you'll consume memory (to track the function calls) for each bad response. Instead, just use a loop.
while true; do
read -r -p "yes or no question [Y/N] " response
case "$response" in
Y|y)
# some code
;;
N|n)
# more code
;;
*) echo "please provide a valid response"
continue ;;
esac
break
done
I just need an example of script that repeat all the same actions in a loop til we ask to stop it. Say I want the user to type y or n for exit, how would i implement it. I have something like
echo "Input y or n to exit"
read input
if [ "$input = y ]
then
.......
else
........
fi
For the same script demonstrated in the answer below or maybe other example, how can I have this addition to make the user control the script without having to exit only by pressing control+z
while true; do echo hello; sleep 1; done
will run until you send a signal.
while true; do
commands ...
read -p "Continue (y/n) ? " answer
case "$answer" in
Y*|y*) : ;;
*) break
esac
done
If the user responds with "Y" or "y", do nothing, in which case the loop continues. Otherwise break the loop.