Bash read command with cat and pipe-CodePudding

I have two scripts:

install.sh

#!/usr/bin/env bash

./internal_install.sh

internal_install.sh

#!/usr/bin/env bash
set -x
while true; do
    read -p "Hello, what's your name? " name
    echo $name
done

When I run ./install.sh, all works as expected:

> ./install.sh 
  true
  read -p 'Hello, what'\''s your name? ' name
Hello, what's your name? Martin
  echo Martin
Martin
...

However, when I run with cat ./install.sh | bash, the read function does not block:

cat ./install.sh | bash
  true
  read -p 'Hello, what'\''s your name? ' name
  echo

  true
  read -p 'Hello, what'\''s your name? ' name
  echo

...

This is just a simplified version of using curl which results in the same issue:

curl -sl https://www.conteso.com/install.sh | bash

How can I use curl/cat to have blocking read in the internal script?

CodePudding user response：

read reads from standard input by default. When you use the pipe, standard input is the pipe, not the terminal.

If you want to always read from the terminal, redirect the read input to /dev/tty.

#!/usr/bin/env bash
set -x
while true; do
    read -p "Hello, what's your name? " name </dev/tty
    echo $name
done

But you could instead solve the problem by giving the script as an argument to bash instead of piping.

bash ./install.sh

When using curl to get the script, you can use process substitution:

bash <(curl -sl https://www.conteso.com/install.sh)