Conditional Executability (GNU Coreutils 9.0)
From Get docs
Coreutils/docs/latest/Conditional-Executability
Next: Multiple Changes, Previous: Changing Special Mode Bits, Up: Symbolic Modes [Contents][Index]
27.2.4 Conditional Executability
There is one more special type of symbolic permission: if you use ‘X’ instead of ‘x’, execute/search permission is affected only if the file is a directory or already had execute permission.
For example, this mode:
a+X
gives all users permission to search directories, or to execute files if anyone could execute them before.
