Linux – Can not run executable files from a mounted drive

The issue is that the script is not what is running, but the interpreter (bash, perl, python, etc.). And the interpreter needs to read the script. This is different from a "regular" program, like ls, in that the program is loaded directly into the kernel, as the interpreter would. Since the kernel itself is reading program file, it doesn't need to worry about read access. The interpreter needs to read the script file, as a normal file would need to be read.

The core of the issue is that you're trying to run the program, which is console application, but you don't have terminal attached to it. In terminal you can run your program by just calling the program name, but in GUI you need to specify explicitly that there should be a terminal window raised to run console apps (this is particularly true of GNOME-based desktops, such as Ubuntu's Unity).

What should be done is that you also need to create a .desktop file for your program with 4 fields. Here's an example:

[Desktop Entry]
Name=MyProg
Type=Application
Exec=/home/xieerqi/example_directory/hello_world_prog
Terminal=true

I don't know about CentOS, but as far as Ubuntu goes, it's the requirement that .desktop applications must be made executable also if they are located in any directory under user's home directory. .desktop files that live in other directories, such as /usr/share/applications do not require that.

So, once you have the .desktop file in place, and made it executable, you will be able to run the program. The important bit is Terminal=true line. That's what will tell GUI to raise a terminal and run your program there. NOTE: if your program executes stuff and exits immediately, you will need to have some sort of delay or getchar(); call just to keep the window open, because terminal window will exit when program exits. That's why many users are sometimes confused "Why is my program not running?" It runs, in reality, it just exits too fast.

Additional notes:

• get rid of system("read -p 'Press Enter to EXIT...' var"); . The read call is a shell built in, and is not a standalone program, which means it only can be used if you use a shell, such as bash. If you are using C, do it properly using scanf() or getchar() to add delay to your program. It is present after return 0; line which means your system() line won't be reached (the program will just quit at return statement), so your placement of the pause for the program is also invalid.
• Read this post on AskUbuntu for example of proper .desktop file with links to official documentation.
• If you are feeling lazy and don't want to make .desktop files for each and every executable file, there's plenty of solutions here. I even posted a script there as well.