Final answer:
The line from Whitman's poem uses personification, attributing human actions to inanimate objects like the flag 'flung' and the bugle 'trills' to evoke a lively and emotional scene.
Step-by-step explanation:
The poetic device utilized in the excerpt from Whitman's poem, "For you the flag is flung--for you the bugle trills," is personification. Personification is a figure of speech where non-human things are given human characteristics. In this line, the flag and the bugle are described as performing actions typically associated with people: 'flung' and 'trills,' respectively, suggesting that these inanimate objects are actively participating in celebrating or honoring the person addressed. This device helps to create a more vivid and emotive scene in the reader's mind.