There are three kinds of file permissions: read, write, and execute. To inspect them, execute the long version of ls:
This shows the total size of the files in kilobytes, followed by information about individual files in eight columns:
1. File type and permissions: The first character is the file type; the two most important file types are ordinary file (-), and directory (d). The next nine characters are divided into three blocks of the three permissions already mentioned: read (r), write (w), and execute (x). Permissions not granted are shown as hyphens. The first three permissions concern the user, that is you, the second the group, and the third the world, which is everybody.
2. Number of links; for files this is usually one, but directories may contain a greater number of links.
3. User name.
4. Group name.
5. File size in characters.
6. Date on which the file was last altered.
7. Time when the file was last altered.
8. File name. We can make drawGenes.sh executable:
Check the result
Now you can run
What happens if you drop ./ from this command