An error occurred when running the chmod command.

When using the chmod command, a problem occurs-General Linux technology-Linux programming and kernel information. For more information, see the following. (The version is fedora 8) use vi to create a file a3 in the/home directory. the code in this file is #! /Bin/bash echo 1111111111, after ls-l, its permission is-rw-r -- and the permission to use the command/home/a3 is not allowed. Then change the chmod u + x a3 permission to-rwxr -- r --. The question is why only permission x is changed, and the group permission and execution permission of other users are not enabled. After the chmod 755 a3 command is used, the permission is changed to-rwxr-xr-x?