Command to prompt for confirmation before executing another command in Shell script

Question

I am using below command to open, replace, view the change and save a file:

sed 's/old string/new string/g' filename > filename1; diff filename1 filename; mv filename1 filename

Is it possible to ask for a confirmation before executing mv command, something like below?

sed 's/old string/new string/g' filename > filename1
diff filename1 filename

<Some-Command here for user to provide Yes or NO confirmation>

mv filename1 filename

The intent is to validate the change and only then save it.

Answer 1

I use this simple one liner on bash:

echo -n 'Confirm: ' && read 'x' && [ $x == 'y' ] && <command>.

This way I do not depend on another utility and it will run only when input is single y.

Answer 2

Yes, you can read user input into a variable via read, and then compare with some acceptable value, like "yes". Also you can store the command in the variable and print it to user and execute it later.

#!/bin/bash

COMMAND='mv filename1 filename'

echo "Perform the following command:"
echo
echo "    \$ $COMMAND"
echo
echo -n "Answer 'yes' or 'no': "

read REPLY
if [[ $REPLY == "yes" ]]; then
    $COMMAND
else
    echo Aborted
    exit 0
fi

Answer 3

My Script is ,

#!/bin/bash


sed 's/This/It/g' test.xml > "test.xml1"

diff test.xml test.xml1

COMMAND ='mv test.xml1 test.xml'

echo "Perform the following command:"
echo
echo "   \$ $COMMAND"
echo
echo -n "Answer 'yes' or 'no':"

read REPLY 

if[[$REPLY=="yes"]]; then
$COMMAND

else 

echo Aborted

exit 0

fi  

The error on executing is,

2c2
< This is a Test file
---
> It is a Test file
./test.sh[9]: COMMAND:  not found
Perform the following command:

   $

-n Answer 'yes' or 'no':
yes
./test.sh[19]: syntax error at line 20 : `then' unexpected

mv command didn't work.