The chmod command in Linux is used to change the access permissions of files and directories². The chmod command can also be used to make shell scripts (files with .sh extension) executable, which means that they can be run as commands.

To use chmod to make .sh files executable, you need to specify the target file(s) and the permission mode. The permission mode can be expressed in either symbolic or numeric notation³.

The symbolic notation consists of three parts: the user class (u for owner, g for group, o for others, a for all), the operator (+ for adding, - for removing, = for setting), and the permission type (r for read, w for write, x for execute).

For example, to add the execute permission for the owner of a file named script.sh, you can use the following command:

The numeric notation consists of three or four digits that represent the permissions for the owner, group, others, and optionally a special mode. Each digit is a sum of values for read (4), write (2), and execute (1).

For example, to set the permissions of script.sh to 755, which means read, write, and execute for the owner, and read and execute for the group and others, you can use the following command:

You can also use wildcards (*) to match multiple files with the same extension. For example, to make all .sh files in the current directory executable for the owner, you can use the following command:

To make a .sh file executable for all users, you can use either of the following commands:

Note: To run a .sh file as a command, you need to either provide the full path to the file or use ./ before the file name. For example:

You may also need to use sudo before the chmod command if you are not the owner of the file or if you want to change the permissions for other users¹. For example: