Added linux_has_systemd_service(): check if systemd unit file is installed

sources/lib/core/include_os.sh

@@ -212,6 +212,24 @@ print ${_HAS_NM}
 return 0
 }
 
+# -----------------------------------------------------------------------------
+# @(#) FUNCTION: linux_has_systemd_service()
+# DOES: check if a systemd service is present (unit file)
+# EXPECTS: name of service [string]
+# OUTPUTS: 0=not installed; 1=installed
+# RETURNS: 0=success; 1=error
+# REQUIRES: n/a
+function linux_has_systemd_service
+{
+(( ARG_DEBUG > 0 && ARG_DEBUG_LEVEL > 0 )) && set "${DEBUG_OPTS}"
+typeset _RC=0
+
+systemctl list-unit-files 2>/dev/null | grep -c "^{$1}" 2>/dev/null
+_RC=$?
+
+return ${_RC}
+}
+
 #******************************************************************************
 # END of script
 #******************************************************************************