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' ] && [ $reply != 'y' ] && echo 'Aborting' && exit 1
echo 'Scary thing'
The other answers have the background on that -n1 flag and other options for read. The echo '' in the 2nd variant is to make subsequent output appear on a new line since the user doesn't have to press Return, so no newline has been echoed to the terminal.
When I run this script the first question it asks is "Would you like to use curl? [Y/N]:" to which my reply is often Y or y. However, when I do that the instant output I get is "Unknown!". I'm expecting to see the next question from the code which is "Great, do you want to ignore certificates [Y/N]: "
Can anyone edit my code to make it work as expected? And tell me why?
#!/bin/bash
echo "Build command"
read -r -e -p "Would you like to use curl? [Y/N]: "
curlstring="curl"
if [[ "${input,,}" == "y" ]]; then
read -r -e -p "Great, do you want to ignore certificates [Y/N]: " input
if [[ "$input" == "y" ]]; then
curlstring=$curlstring" -k"
else
curlstring=$curlstring" "
fi
echo "$curlstring"
elif [[ "${input,,}" == "n" ]]; then
echo "Bye"
else
echo "Unknown!"
exit 0
fi
The error is your are not actually capturing the user input from the first read command, change it,
read -r -e -p "Would you like to use curl? [Y/N]: " input
Also bash is quite sensitive about the constructs used, the line number 15
fi echo "$curlstring"
will likely throw a syntax error saying below when you give a Y or a y as one of the options,
Would you like to use curl? [Y/N]: Y
script.sh: line 15: syntax error near unexpected token `echo'
script.sh: line 15: ` fi echo "$curlstring" '
change it to separate lines.
I recently created a different thread with an issue concerning a for loop in a bash script I was writing for my GCSE coursework. I have another issue with the same bash script (however it has evolved a fair bit since last time).
Here is the code:
#!/bin/bash
# A script that creates users.
uerror='^[0-9]+$'
echo "This is a script to create new users on this system."
echo "How many users do you want to add? (in integer numbers)"
read am
echo " "
if [[ $am =~ $uerror ]] ; then
echo "ERROR: Please use integer numbers."
echo "Please re-enter the amount."
read am ;
else
echo " "
for i in $(seq "$am")
do
echo "Enter a username below:"
read usern
sudo useradd $usern
sudo passwd $usern
echo " "
echo "User $i '$usern' added."
echo " "
echo "What group do you want to add $usern to?"
read group
sudo usermod $usern -aG $group
echo "$usern added to $group"
echo " "
echo "-------------------"
echo " "
done
fi
The issue is in the if statement. It's purpose is to stop users entering anything other than an integer number. But for some reason, I don't seem to be able to capture the input from the read am part. Instead the script skips straight onto the for loop where the $(seq "$am") obviously will have issues comprehending an input that is not a number.
The output from this error is as follows.
seq: invalid floating point argument
However, I don't think this is relevant because as far as I can tell, the issue is with the if / else statement.
If anyone could point me in the right direction of what I need to do to fix this, I would be greatly appreciative.
I'd also like to iterate that I am still learning how to write bash scripts (and not in a particularly organised manner) so I've probably made a very simple mistake. Apologies for that.
Thanks,
Callum.
EDIT: I mistyped an echo message, I've now changed that so it actually makes sense.
If you want to read in a number and make sure it is a number use a while loop:
while read -p 'type a number:' n ; do
# Exit the loop if the input is a number
[[ "$n" =~ ^[0-9]+$ ]] && break
echo "This was not a number! Don't trick me!"
done
# Now can use `seq`
seq "$n"
The if statement in your example would do the completely the wrong thing. It checks if the input is a number and in that case asks for the input again and exits the script. If you don't type a number, it uses the (wrong) input in the else branch.
Replace your whole file with this:
#!/bin/bash
# A script that creates users.
uerror='^[0-9]+$'
echo "This is a script to create new users on this system."
echo "How many users do you want to add? (in integer numbers)"
read am
echo " "
while true; do
if [[ $am =~ $uerror ]] ; then
break;
else
echo "Must be integer"
echo "Please re-enter: "
read am ;
fi
done
for i in $(seq "$am")
do
echo "Enter a username below:"
read usern
sudo useradd $usern
sudo passwd $usern
echo " "
echo "User $i '$usern' added."
echo " "
echo "What group do you want to add $usern to?"
read group
sudo usermod $usern -aG $group
echo "$usern added to $group"
echo " "
echo "-------------------"
echo " "
done
I read a lot about passing piping stdin to bash read function, but nothing seems to work for my bash version!!
GNU bash, version 3.2.51(1)-release (x86_64-suse-linux-gnu)
I have a bash script that in some point asks the user "yes/no" with variable CONTINUEQUESTION:
echo "Do you want to continue? (yes/no):"
read CONTINUEQUESTION
tmp=$(tr '[:upper:]' '[:lower:]' <<<$CONTINUEQUESTION)
if [[ "$tmp" != 'y' && "$tmp" != 'yes' ]]; then
echo "Aborting because of input '$CONTINUEQUESTION'"
exit
fi
I would like to pipe a "yes or no" to this question without user input!
Yes i know i could use expect, but i don't prefer it in this case.
So i tried several things:
CONTINUEQUESTION='yes'
echo $CONTINUEQUESTION | ./myscript.sh
Aborting because of input ''
./myscript.sh <<< "$CONTINUEQUESTION"
Aborting because of input ''
...and many other, nothing worked!?
O.k. now I did a bit revers thinking and find out that the below line causes the problem with the pipe...because when i remarked it out all the below answers are working just fine, but not when this line is executed:
running=`ssh root#${HOSTNAME} 'su - root -c "/bin/tools list | grep \"system running\"" 2>&1'`
But, i need this line before the read! What do i need to reverse the 2>&1????
My script look like this and is working without this try to over come the user intervantion:
LIST_FILE_NAME=$1
STILL_RUNNING=0
running=`ssh root#${HOSTNAME} 'su - root -c "cat '$LIST_FILE_NAME' | grep \"system running\"" 2>&1'`
if [[ $running =~ .*running.* ]]; then
STILL_RUNNING=1
echo "NODE $NODE running stop before continuing."
fi
if [ $STILL_RUNNING -eq 1 ]; then
echo "Aborting system was still running!"
exit 1
fi
echo "Do you want to continue? (yes/no):"
read CONTINUEQUESTION
tmp=$(tr '[:upper:]' '[:lower:]' <<<$CONTINUEQUESTION)
if [[ "$tmp" != 'y' && "$tmp" != 'yes' ]]; then
echo "Aborting because of input '$CONTINUEQUESTION'"
exit
fi
echo "o.k."
4 points:
list.log can have a line with "system running" or "system notrunning"
if list.log has a line with "system notrunning" than the bash script continue towards the question
at the question i never got it right to inject the 'y' or 'yes' so the bash aborts because of input ''
i execute this like: ./myscript.sh list list.log (normal way)
This bash runs well if the user interacts at the question!
Thanks for you time!!!
Consider this variation as well:
#!/bin/bash
read -p "Do you want to continue? (yes/no): " CONTINUEQUESTION
if [[ $CONTINUEQUESTION != [Yy] && $CONTINUEQUESTION != [Yy][Ee][Ss] ]]; then
echo "Aborting because of input '$CONTINUEQUESTION'."
exit
fi
Tested with:
bash script.sh <<< yes
If it doesn't work, show the output of:
bash -x script.sh <<< yes
Your line
$CONTINUEQUESTION='yes'
shoul really be
CONTINUEQUESTION='yes'
I am not sure then that your are feeding stdin with the word 'yes'. You could add an echo after the read to be sure.
You can use heredoc:
bash -ex ./myscript.sh << 'EOF'
yes
EOF
Search for Here Documents in man bash.
EDIT: Based on comments you can use this ssh command:
running=$(ssh -t -t root#${HOSTNAME} "grep 'system running' \"$LIST_FILE_NAME\"")
So somebody showed me how to use condition(s) to test if a user had typed input for a password.
I wanna take a their example a step further and use a loop (at least thats what I think it's call).
Here is their example:
read -s -p "Enter new password: " NEWPASS
if test "$NEWPASS" = ""; then
echo "Password CAN NOT be blank re-run sshd_config"
exit 1;
fi
Instead of exiting the script I want it to keep asking for the input until there is some.
I wanna make a statement like this but I was doing it wrong:
(Now using top example)
The user is given a chance to enter new password and fill the variable value.
read -s -p "Enter new password:" NEWPASS
echo ""
The next portion checks the variable to see if it contains a value, while the value is null it request the user to fill the value indefinitely. ( a loop)
while [[ -z "$NEWPASS" ]]; do
echo ""
echo "Password CAN NOT be blank"
echo ""
read -s -p "Enter new password:" NEWPASS;
echo ""
done
This line searches a file containing a set of variables used by another file. It then searches the file for a line containing PASS=.* (.* meaning anything) then writes PASS=$NEWPASS ($NEWPASS being variable)
sed -i -e"s/^PASS=.*/PASS=$NEWPASS/" /etc/sshd.conf
Thank you for all the help, I'm going to use this and learn from it.
This while loop should work:
while [[ -z "$NEWPASS" ]]
do
read -s -p "Enter new password: " NEWPASS
done
while read -s -p 'Enter new password: ' NEWPASS && [[ -z "$NEWPASS" ]] ; do
echo "No-no, please, no blank passwords!"
done