Passing variables from sh to expect not working with docker-compose

Question

The Dockerfile contains:

ENV VAR 1
COPY ./setup.exp /tmp/
RUN chmod a+x /tmp/setup.exp

The expect file:

#!/usr/bin/expect
set timeout -1
spawn setup -v
expect "Enter variable: "
send -- "$env(VAR)\r"

The shell file (main.sh):

#!/bin/sh
/tmp/setup.exp $VAR

When I run ./main.sh from the shell inside the container, it works perfectly fine.

However, when I run docker-compose up with entrypoint: ./main.sh, it prints this error:

send: spawn id exp4 not open
    while executing
"send -- "$env(VAR)\r""
    (file "/tmp/setup.exp" line 5)

If I pass the variable directly as entrypoint: /tmp/setup.exp ${VAR}, it prints this warning:

WARNING: The VAR variable is not set. Defaulting to a blank string.

I also tried set VAR [lindex $argv 0]; and then send -- "$VAR\r" without any success.

Seems like from inside the container the script is able to load docker's env variables.

Any suggestions?

Answer 1

Thanks @glennjackman for pointing that out. I ran expect -d for a more verbose output.

It turns out the reason the program exited is because python was raising this exception:

ValueError: invalid width 0 (must be > 0)

Setting the variable say ENV COLUMNS 100 in the Dockerfile solved the issue for me.