Marcy is an inveterate shopper who is always on the qui vive for bargains. —— Merriam-Webster

My wife and I sold the trailer in 1986 and bought a small house in an unincorporated chunk of Los Angeles County, adjacent to Pasadena on the east. Of twenty households on our block, one is Asian (Chinese), two African-American, and one Latino (he is Puerto Rican, she is Mexican). None of the houses on the block is large enough to accommodate live-in help, but several of us do employ gardeners. All the gardeners are Latino, and when a slight brown man walks down a driveway, he is understood to be there for good reason. Were a tail black man to do the same, there is not one of us who would not immediately be on the qui vive. My sadness about the American estrangement just mentioned doesn't make me act any differently at such a moment. —— Jack Mile in 'Blacks vs. Browns'; The article illustrates that behind the Los Angeles riot lay a grim economic competition between Latinos and African-Americans, which is intensifying and which poses a stern challenge to U.S. domestic and foreign policy, as well as to sentimental cultural attitudes about immigration; The Atlantic; Oct 1992

Naturally, in the absence of a free press, and with Gadafy's "purification committees" ever on the qui vive for seditious thinking, it is hard to know just how far Libya has moved away, in O'Brien's words, from being a pariah. But I would put it at around two inches. Pick any line from the 1948 Universal Declaration of Human Rights, and the chances are that Libya, or at least Gadafy, its Brother Leader and Guide of the Revolution, takes a contrary view. —— Catherine Bennett; Gadafy - Human Rights Crusader; August 22, 2002

Did you know? (Merriam-Webster)
When a sentinel guarding a French castle in days of yore cried, "Qui vive?" your life depended upon your answer (the right one was usually something like "Long live the king!"). What the sentinel was asking was "Long live who?" but the act of calling out apparently impressed English listeners more than the meaning of the phrase, because when they adopted it in the early 1700s they used "qui vive" in the sense "alert." Nowadays, it is most often used in the phrase "on the qui vive," meaning "on the lookout."