envsubst

• https://www.gnu.org/software/gettext/manual/html_node/envsubst-Invocation.html

Usage: envsubst [OPTION] [SHELL-FORMAT]

Substitutes the values of environment variables.

Operation mode:
  -v, --variables             output the variables occurring in SHELL-FORMAT

Informative output:
  -h, --help                  display this help and exit
  -V, --version               output version information and exit

In normal operation mode, standard input is copied to standard output,
with references to environment variables of the form $VARIABLE or ${VARIABLE}
being replaced with the corresponding values.  If a SHELL-FORMAT is given,
only those environment variables that are referenced in SHELL-FORMAT are
substituted; otherwise all environment variables references occurring in
standard input are substituted.

When --variables is used, standard input is ignored, and the output consists
of the environment variables that are referenced in SHELL-FORMAT, one per line.

Report bugs in the bug tracker at <https://savannah.gnu.org/projects/gettext>
or by email to <[email protected]>.

envsubst < cluster-config.yaml | eksctl create cluster -f - 

• https://aws.amazon.com/blogs/containers/start-pods-faster-by-prefetching-images/

See also

• gettext, envsubst
• Variables: Environment variables, env, env-cmd, .env/, SHELL, PS1, HOME, $?, PATH, HISTFILE, PWD, LD_LIBRARY_PATH, printenv, getenv, getenv, direnv, AWS cli environmental variables, envsubst, env:, env_file (docker-compose)

https://aws.amazon.com/blogs/containers/start-pods-faster-by-prefetching-images/