Question

I would like to use bash process substitution for a sudo command.

For example, here’s a non-sudo command that works for me:

$ cat <(echo "installed.txt")
installed.txt

And here’s a sudo version of the command that does not work:

$ sudo cat <(echo "installed.txt")
cat: /dev/fd/63: Bad file descriptor

Reading the sudo man page, it seems that sudo closes all but the stdin/stdout/stderr file descriptors before running the command as root. This leads me to think that bash is creating the descriptor (and performing the process substitution) before running the sudo command.

I changed root’s shell to bash (instead of sh default). I’ve tested that the command works fine when logged in as root. It only does not work via a sudo command.

What is the appropriate technique to achieve what I’m trying to do here? Eval, quoting, sudo flag, sudoers file mod, other?

Answer 1

Try doing this in your shell :

$ sudo bash -c 'cat <(echo "installed.txt for UID=$UID")'
installed.txt for UID=0