Bash Heredoc doesn't seem to work with Docker RUN statement

Question

I am trying to use Valve's steamcmd package in a bash script, an interactive shell that takes user input. Of course i'd like to be able to send input manually as part of a docker build, but I'm running into some issues.

I started by installing steamcmd locally and running this script:

./steamcmd <<LOGIN
login anonymous
quit
LOGIN

Unsurprisingly, it works properly, yielding this output:

Steam Console Client (c) Valve Corporation
-- type 'quit' to exit --
Loading Steam API...OK.

Connecting anonymously to Steam Public...Logged in OK
Waiting for user info...OK
Steam>

The problems start when I try the same command in Docker:

RUN ./steamcmd <<LOGIN \
login anonymous \
quit \
LOGIN

During the build, it runs ./steamcmd but then hangs on the input prompt, none of the data in the Heredoc is passed and the build never completes. What am I doing wrong?

Extra Info:

• Base Image: ubuntu:latest
• User: non root

Answer 1

The Docker build process is completely non-interactive, and if you are looking for some input then you need to pass build-args, and the reference these build-args in your sub-sequent RUN command.

But as mentioned in the commend you need to run them as a CMD as it will stuck the build process.

Here is Dockerfile with some example entrypoint that may help you,

# start steamcmd to force it to update itself
RUN ./steamcmd/steamcmd.sh +quit

# start the server main script
ENTRYPOINT ["bash", "/home/steam/server_scripts/server.sh"]

You can change it to

/home/steam/steamcmd/steamcmd.sh \
    +login anonymous \
    +exit

and one example from above list is cs_go.sh which you need to rename to server.sh is

#!/bin/bash

# update server's data
/home/steam/steamcmd/steamcmd.sh \
    +login anonymous \
    +force_install_dir /home/steam/server_data \
    +app_update 740 \
    +exit

# start the server
/home/steam/server_data/srcds_run \
    -game csgo -console -usercon \
    -secure -autoupdate -tickrate 64 +hostport 27015 \
    +game_type 0 +game_mode 1 +mapgroup mg_active +map de_dust2 \
    -port 27015 -console -secure -nohltv +sv_pure 0 +ip 0.0.0.0

exit 0

updated:

Automating SteamCMD

There are two ways to automate SteamCMD. (Replace steamcmd with ./steamcmd.sh on Linux/OS X.)

Command line

Note: When using the -beta option on the command line, it must be quoted in a special way, such as +app_update "90 -beta beta".

Note: If this does not work, try putting it like "+app_update 90 -beta beta" instead.

Append the commands to the command line prefixed with plus characters, e.g.:

steamcmd +login anonymous +force_install_dir ../csgo_ds +app_update 740 +quit

Automating SteamCMD