I wrote a text file with some linux shell commands and I tried to make it executable with this
sudo chmod a+x filename
But when I am clicking the file it is opening in the text editor. While checking the properties I found it is not executable at all. How to make it executable.
It is unclear what you mean with textfile in the first version of your question. To run it as program it can be a source file or a script. A source file must be compiled with a compiler like gcc to get an executable binary program. With a script you need an interpreter.
I assume you mainly mean to execute a script. Executing it is only possible with an interpreter like bash, python, perl, awk, sed or any other known interpreter. If you want to make it executable you have to tell the operating system what interpreter it has to use. This is done with the first line in the script, a so called shebang. For a bash script you have to insert as first line
#!/bin/bash
For a python script it could be
#!/usr/bin/python3
or better
#!/usr/bin/env python3
Similar lines are needed for other interpreter.
If you have added the shebang then you must make the script executable as you already have done with:
rpi ~$ sudo chmod a+x filename
rpi ~$ ls -l filename
-rwxr-xr-x 1 pi pi 0 Oct 22 18:26 filename
Notice the three x in the modes. If you want to execute the script from the same directory you are in you have to prefix ./ to avoid unwanted execution:
rpi ~$ ./filename
./ is to add the directory with the script(s) to your PATH environment.
#!/bin/bash to the script, make it executable, as both described in the answer and double click it in the GUI.
#!/bin/bash, even though best practice, is not required if you start from the shell. If it is missing, the GUI however will probably not execute it with bash as interpreter.
Commented
Oct 22, 2019 at 20:59