The writ may be either alternative or peremptory. The alternative writ must command the party to whom it is directed, immediately after the receipt of the writ, or at some other specified time, to do the act required to be performed or to show cause before the court at a specified time and place why he has not done so. The peremptory writ must be in a similar form, except that the words requiring the party to show cause why he has not done as commanded must be omitted and a return day inserted.
SOURCE: CCP § 1087.