How do I prompt a user for confirmation in bash script

Question

I want to put a quick  are you sure   prompt for confirmation at the top of a potentially dangerous bash script  what s the easiest best way to do this

User · Answer

Try the read shell builtin   read -p  Continue  y n    CONT if     CONT     y     then   echo  yaaa   else   echo  booo   fi

User · Answer

use case esac    read -p  Continue  y n    choice case   choice  in    y Y   echo  yes      n N   echo  no          echo  invalid    esac   advantage     neater can use  OR  condition easier can use character range  eg  yY  eE  sS  to accept word  yes   where any of its characters may be in lowercase or in uppercase

User · Answer

-f     sname      amp  amp  read -p  File exists  Are you sure    -n 1        REPLY      Yy       amp  amp  exit 1   used this in a function to look for an existing file and prompt before overwriting

User · Answer

bin bash echo Please  enter your name read NAME echo  Hi  NAME   if    x NAME     xyes      then    do something fi   I s a short script to read in bash and echo back results

User · Answer

Here s the function I use    function ask yes or no         read -p   1   y es or  N o         case   echo  REPLY   tr   A-Z     a-z    in         y yes  echo  yes                    echo  no         esac     And an example using it   if     no       ask yes or no  Are you sure                no       ask yes or no  Are you  really  sure       then     echo  Skipped       exit 0 fi    Do something really dangerous       The output is always  yes  or  no  It s  no  by default Everything except  y  or  yes  returns  no   so it s pretty safe for a dangerous bash script And it s case insensitive   Y    Yes   or  YES  work as  yes     I hope you like it  Cheers

User · Answer

qnd  use   read VARNAME echo  VARNAME   for a one line response without readline support   Then test  VARNAME however you want

User · Answer

echo are you sure  read x if     x     yes    then     do the dangerous stuff fi

User · Answer

read -p  quot Are you sure   quot  -n 1 -r echo       optional  move to a new line if     REPLY      Yy      then       do dangerous stuff fi  I incorporated levislevis85 s suggestion  thanks   and added the -n option to read to accept one character without the need to press Enter  You can use one or both of these  Also  the negated form might look like this  read -p  quot Are you sure   quot  -n 1 -r echo       optional  move to a new line if       REPLY      Yy      then         quot  0 quot     quot  BASH SOURCE quot      amp  amp  exit 1    return 1   handle exits from shell or function but don t exit interactive shell fi  However  as pointed out by Erich  under some circumstances such as a syntax error caused by the script being run in the wrong shell  the negated form could allow the script to continue to the  quot dangerous stuff quot   The failure mode should favor the safest outcome so only the first  non-negated if should be used  Explanation  The read command outputs the prompt  -p  quot prompt quot   then accepts one character  -n 1  and accepts backslashes literally  -r   otherwise read would see the backslash as an escape and wait for a second character   The default variable for read to store the result in is  REPLY if you don t supply a name like this  read -p  quot my prompt quot  -n 1 -r my var The if statement uses a regular expression to check if the character in  REPLY matches      an upper or lower case  quot Y quot   The regular expression used here says  quot a string starting     and consisting solely of one of a list of characters in a bracket expression   Yy   and ending     quot   The anchors    and    prevent matching longer strings  In this case they help reinforce the one-character limit set in the read command  The negated form uses the logical  quot not quot  operator     to match      any character that is not  quot Y quot  or  quot y quot   An alternative way to express this is less readable and doesn t as clearly express the intent in my opinion in this instance  However  this is what it would look like  if     REPLY       Yy

User · Answer

This what I found elsewhere  is there a better possible version   read -p  Are you sure you wish to continue   if     REPLY      yes     then    exit fi

User · Answer

This way you get  y   yes  or  Enter    read -r -p  Are you sure   Y n   response  response   response      tolower  if     response      yes y             -z  response     then     your-action-here  fi   If you are using zsh try this   read  response Are you sure    Y n    response   response l   tolower if     response      yes y             -z  response     then     your-action-here fi

[bash] How do I prompt a user for confirmation in bash script?

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