Test script to test generic shell command with the environment of a specific systemd unit

emulate-systemd-unit.sh

#!/usr/bin/env bash

set -euo pipefail

function escape_shell_command() { for arg in "${@}"; do printf '%q ' "$arg"; done; }

command="$1"
unit="$2"

testUnit="test-$unit"
testCommand="$(escape_shell_command "${@:3}")"

systemdRunCommand="$(

systemctl show "$unit" \
| grep -E '(^(User|Group|Supplementary|Protect|Private|Restrict|Lock|NoNew|Environment|SystemCallFilter)|(Capabilit|Deny))' \
| while IFS= read -r property; do printf "%q\\n" "$property"; done \
| awk -v "unit=$testUnit" -v "command=${testCommand//\\/\\\\}" '
BEGIN { printf("\nsystemd-run --pty -u '\''%s'\'' --collect --wait \\\n", unit) }
/^EnvironmentFiles=/ {
        prefix = ($0 ~ / \\\(ignore_errors=yes\\\)$/) ? "-" : "";
        value = gensub(/^EnvironmentFiles=(.*)\\ \\\(ignore_errors=(yes|no)\\\)$/, "\\1", "g", $0);
        printf("--property=EnvironmentFile=%s%s \\\n", prefix, value);
        next;
}
1 { printf("--property=%s \\\n",$0) }
END { print "-- " command }
'

)"

if [[ "$command" != "run" ]]; then
        echo "$systemdRunCommand";
        exit
fi

start="$(date --iso=seconds)"

bash -c "$systemdRunCommand" || true

echo
echo Log:
journalctl -u "$testUnit" --since="$start" --no-pager