Bash script is printed instead of executed

This question is similar to this one: https://serverfault.com/questions/342697/prevent-sudo-apt-get-etc-from-swallowing-pasted-input-to-stdin , but the answer is not satisfactory (adding &&

to each line bash script is not nifty) and does not explain why some users can insert / execute multiple subsequent commands apt-get install -y

and others cannot because stdout is bloated by the next command.

I have a script my_script.sh

:

sudo apt-get install -y graphicsmagick
sudo apt-get install -y libgraphicsmagick++1-dev
...

      

        
        
        
      

    

It can only have two lines or more sudo apt-get install

. Libraries (graphicsmagick, etc.) Doesn't matter, it can be any library.

When I copy this script and paste its contents into bash, or simply execute it like this:

cat my_script.sh | sudo -i bash

      

        
        
        
      

    

then for some reason only the first line (graphicsmagick) gets executed and the rest is just printed to the console. This only happens with sudo apt-get install -y

, other scripts that do not contain this command behave normally.

If I change bash

to sh

(which is dash

) I get the expected behavior:

cat my_script.sh | sudo -i sh

      

        
        
        
      

    

Can you explain why this is happening?

By answering questions, you can avoid these questions / comments:

• Why are you doing this?
• The pipeline to your bash is not secure
• Some other aspects are not secure or hacky.

I just want to know why it bash

doesn't work the way I would expect and sh

does.

PS. I am using Ubuntu 14.04, sh is a dash, as you can see here:

vagrant@vagrant-ubuntu-trusty-64:/tmp$ ls -l /bin/sh
lrwxrwxrwx 1 root root 4 Feb 19  2014 /bin/sh -> dash