In your Github action page the env indentation is off.

It used to work and now encountering below error:

Build container for action use: '/home/runner/work/_actions/danielr1996/envsubst-action/1.1.0/Dockerfile'.
/usr/bin/docker build -t 7db2d7:4d9576c05def46a6906f7d9ef5a712e4 -f "/home/runner/work/_actions/danielr1996/envsubst-action/1.1.0/Dockerfile" "/home/runner/work/_actions/danielr1996/envsubst-action/1.1.0"
Sending build context to Docker daemon 8.192kB

Step 1/5 : FROM alpine
latest: Pulling from library/alpine
59bf1c3509f3: Already exists
Digest: sha256:21a3deaa0d32a8057914f36584b5288d2e5ecc984380bc0118285c70fa8c9300
Status: Downloaded newer image for alpine:latest
---> c059bfaa849c
Step 2/5 : RUN apk --update add gettext
---> Running in 0d3a56ebeddb
fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.[15](https://github.com/leightonasia/cpcs6-powerflow/runs/5193786466?check_suite_focus=true#step:2:15)/community/x86_64/APKINDEX.tar.gz
ERROR: https://dl-cdn.alpinelinux.org/alpine/v3.15/main: temporary error (try again later)
WARNING: Ignoring https://dl-cdn.alpinelinux.org/alpine/v3.15/main: No such file or directory
ERROR: https://dl-cdn.alpinelinux.org/alpine/v3.15/community: temporary error (try again later)
WARNING: Ignoring https://dl-cdn.alpinelinux.org/alpine/v3.15/community: No such file or directory
ERROR: unable to select packages:
gettext (no such package):
required by: world[gettext]
The command '/bin/sh -c apk --update add gettext' returned a non-zero code: 1

This use to worked but today I encountered an issue:

envsubst not found

This use to worked but today I encountered an issue:

envsubst not found

• Is there a way to substitute multiple files with the same variable.

Also improvement:
If there would be an option for in-place substitution, and hence I wouldn't have to specify the output file.