But meaning ‘except’

But can mean ‘except’ after words like all, none, every, any, everything, everybody, nothing and no.

He eats nothing but French fries. (= He eats nothing except French fries.)
She did nothing but cry. (= She did nothing except cry.)

Pronouns after but
After but, we usually use object pronouns (e.g. me, him, her etc.) Subject pronouns (I, he etc) are possible in a more formal style.

Nobody but her would trust him. (More formal: Nobody but she would trust him.)

Verbs after but

The form of the verb used after but usually depends on what came before.

She does nothing but eat. (Here we use a simple present tense form before and after but.)
She is not interested in anything but writing. (Here we use an –ing form after but because interested in is usually followed by an –ing form.)

After but, infinitives are normally used without to.

‘Cannot but + infinitive’ and ‘cannot help but + infinitive’ are sometimes used with the meaning of ‘can’t help…ing’

You can’t help but admire his courage. OR You can’t but admire his courage. (= You have to admire his courage.)