From a5aa4edffdd86a9edf884c08b29cf8c4da13b44a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marco=20Trevisan=20=28Trevi=C3=B1o=29?= <mail@3v1n0.net>
Date: Tue, 29 Dec 2020 00:50:54 +0100
Subject: [PATCH] installer.sh: Properly check for enabled ModemManager service
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A systemd service may be marked as enabled as vendor preset, and this
breaks the check we used to check if it was active.

Here's what you get in an Ubuntu 20.04 installation:

❯ sudo systemctl status ModemManager
● ModemManager.service - Modem Manager
     Loaded: loaded (/lib/systemd/system/ModemManager.service; disabled; vendor preset: enabled)
     Active: inactive (dead)

❯ systemctl list-unit-files ModemManager.service
UNIT FILE            STATE    VENDOR PRESET
ModemManager.service disabled enabled

1 unit files listed

While the list-unit-files can be filtered using `--state=enabled`, we
can just rely on `systemctl is-enabled` instead.
---
 installer.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/installer.sh b/installer.sh
index e019c0c..e0757d4 100644
--- a/installer.sh
+++ b/installer.sh
@@ -63,7 +63,7 @@ if [ ! -z "${MISSING_PACKAGES}" ]; then
 fi
 
 # Check if Modem Manager is enabled
-if systemctl list-unit-files ModemManager.service | grep enabled > /dev/null 2>&1; then
+if systemctl is-enabled ModemManager.service &> /dev/null; then
     warn "ModemManager service is enabled. This might cause issue when using serial devices."
 fi