Unable to accept user input in bash

user_2464664 0
Viewed 110
while
   echo "Do you want to continue y/n?"
   read install_to_default
   [[ -z $install_to_default || $install_to_default != [yYnN] ]]
do echo "The response is invalid. A valid response is y or n."; done

Running the above script as root causes no problems, but when I try to run the script as a different user with the below changes it causes an infinite loop.

sudo -u piggy -i <<'EOF'
while
    echo "Do you want to continue y/n?"
    read install_to_default
    [[ -z $install_to_default || $install_to_default != [yYnN] ]]
    do echo "The response is invalid. A valid response is y or n."; done
EOF
bash
2 Answers

The stdin of the sudo process has been redirected to the here-document << and the read command in the loop doesn't wait for the user's input on console. Please try to change the read line to:

read -u 1 install_to_default

Technically it may not be the best idea to use descriptor 1 for the purpose. Strictly we should use other descriptor such as 3 with the -C 4 option to the sudo command. But this solution will require to change the sudoers policy which may rather cause more problems.

user_85723800

You cannot read user input this way because the input stream is already captured by the here-document script.

If you want to read user input from the terminal, while using a here-document as the sudo script, then read from /dev/tty

sudo -u piggy -i <<'EOF'
while
    printf %s\\n "Do you want to continue y/n?"
    read -r install_to_default </dev/tty
    [ -z "$install_to_default" ] || [ -n "${install_to_default%[yYnN]}" ]
    do
      printf %s\\n "The response is invalid. A valid response is y or n."
    done
EOF
user_79398710
Related