systemd has an EnvironmentFile directive, which sets environment variables from a file's contents based on a number of rules, which are not quite equivalent to how a shell would parse that file.
How can I parse a systemd EnvironmentFile in exactly the same way that systemd itself would?
The surest thing is to let systemd parse the file itself, via a transient service. Thus:
# emit a NUL-delimited set of key=value definitions for environment variables defined by a set of files
newVarsForFile_nullsep() {
local -a extraParams=( ); local file
(( $# )) || return 0 # no files specified, nothing to do
for file in "$@"; do
extraParams+=( --property=EnvironmentFile="$file" )
done
comm -z -23 \
<(sort -z < <(systemd-run --user --pipe "${extraParams[@]}" grep -zvE '^INVOCATION_ID=' /proc/self/environ </dev/null)) \
<(sort -z < <(systemd-run --user --pipe grep -zvE '^INVOCATION_ID=' /proc/self/environ </dev/null) )
}
# emit code that can be eval'd in an instance of bash to precisely define the exact variables
newVarsForFile_shellscript() {
while IFS= read -r -d '' vardef; do
printf '%s=%q\n' "${vardef%%=*}" "${vardef#*=}"
done < <(newVarsForFile_nullsep "$@")
}
Thereafter, one may invoke (as an example):
newVarsForFile_shellscript /etc/conf.d/*.conf
...to emit a shell script fragment which, when executed by bash, will set all the same environment variables that adding the relevant EnvironmentFiles to a service definition would set.