From 8e2f11b89554f879f13a7bb4371b842bf7feeb46 Mon Sep 17 00:00:00 2001
From: Chengdong Fu <fucd@ihep.ac.cn>
Date: Mon, 5 Dec 2022 17:34:00 +0800
Subject: [PATCH] add error message while cannot open file

---
 Detector/MagneticFieldMap/src/FieldMapFileProvider.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Detector/MagneticFieldMap/src/FieldMapFileProvider.cpp b/Detector/MagneticFieldMap/src/FieldMapFileProvider.cpp
index 2eb352e4..35bd036f 100644
--- a/Detector/MagneticFieldMap/src/FieldMapFileProvider.cpp
+++ b/Detector/MagneticFieldMap/src/FieldMapFileProvider.cpp
@@ -209,6 +209,13 @@ bool FieldMapFileProvider::loadCSV(const std::string& fn,
     std::ifstream input(fn);
     std::string tmpline;
 
+    if (!input) {
+      std::cout << "Open file failure: please check file name and path! " << std::endl;
+      std::cout << "Notice: need absolute path or relative to path to run job!" << std::endl;
+      std::string error_msg = "[ERROR] FieldMapFileProvider: Cannot open " + fn;
+      throw std::runtime_error(error_msg);
+    }
+
     ncol = 0;
     nrow = 0;
 
-- 
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