In UNIX-like OS, which is the correct meaning of the command chmod u+x foo?

The chmod u+x foo command uses u to denote the user (owner), + to add permissions, and x for execute. This grants execute permission exclusively to the file owner without modifying permissions for group or others. Option D is incorrect because the + operator adds permissions without removing existing ones for other users.

Step-by-step Derivation:
Breaking down chmod u+x foo:

• chmod: change mode command
• u: user (file owner)
• +: add permission operator
• x: execute permission
• foo: target filename

Result: Execute permission is added only for the owner. No other permissions are affected or removed. This matches option A exactly.