In the permission expression g+rwX, what does the capital X signify?

• A. The execute permission is granted to all items
• B. The execute permission is added only to directories or items that already have execute
• C. The permission is applied recursively
• D. It revokes execute permission

Answer: (B)

Capital X in a symbolic chmod expression is a conditional execute flag. It means you grant the execute permission only if it’s appropriate for the item: for directories, execute is always allowed; for regular files, execute is granted only if the file already had an execute bit for that class. In g+rwX, you reliably give group read and write, and the execute bit is added only to directories or to files that already had execute for the group (or for any class, depending on current bits). This prevents turning non-executable files into executables by mistake. So the correct interpretation is that the execute permission is added only to directories or items that already have execute.