Fix opening pdf with okular in linux (JabRef#5253)

CHANGELOG.md

@@ -15,6 +15,7 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 
 ### Fixed
 
+- We fixed and issue where pdf files will not open under some KDE linux distributions when using okular. [#5253](https://github.com/JabRef/jabref/issues/5253)
 - We fixed an issue where the Medline fetcher was only working when JabRef was running from source. [#5645](https://github.com/JabRef/jabref/issues/5645)
 - We fixed some visual issues in the dark theme. [#5764](https://github.com/JabRef/jabref/pull/5764) [#5753](https://github.com/JabRef/jabref/issues/5753)
 - We fixed an issue where non-default previews didn't handle unicode characters. [#5779](https://github.com/JabRef/jabref/issues/5779)

src/main/java/org/jabref/gui/desktop/os/Linux.java

@@ -30,7 +30,11 @@ public void openFile(String filePath, String fileType) throws IOException {
             viewer = "xdg-open";
         }
         String[] cmdArray = { viewer, filePath };
-        Runtime.getRuntime().exec(cmdArray);
+        Process p;
+        p = Runtime.getRuntime().exec(cmdArray);
+        BufferedReader in = new BufferedReader(new InputStreamReader(p.getErrorStream()));
+        String line;
+        line = in.readLine();
     }
 
     @Override
@@ -46,7 +50,11 @@ public void openFileWithApplication(String filePath, String application) throws
         String[] cmdArray = new String[openWith.length + 1];
         System.arraycopy(openWith, 0, cmdArray, 0, openWith.length);
         cmdArray[cmdArray.length - 1] = filePath;
-        Runtime.getRuntime().exec(cmdArray);
+        Process p;
+        p = Runtime.getRuntime().exec(cmdArray);
+        BufferedReader in = new BufferedReader(new InputStreamReader(p.getErrorStream()));
+        String line;
+        line = in.readLine();
     }
 
     @Override