Y is a character vector that specifies a valid UNIX user name. The function changes the userid (uid) and groupid (gid) of the process to values that correspond to the specified user name.
Note that it is only possible to change the user name if the effective uid is 0 (that is, the process has root privileges).
If the operation is successful, R is the user name specified in Y. Note that the value of ⎕AN will not be affected, but the value of ⊃⎕AI will be.
If the operation fails, the function generates a FILE ERROR 1 Not Owner error.
If the argument to 4001⌶ is other than a non-empty simple character vector, the function generates a DOMAIN ERROR.
If the argument is not the name of a valid user the function generates a FILE ERROR 3 No such process.
If the argument is the same name as the current effective user, then the function returns that name, but has no effect.
If the argument is a valid name other than the name of the effective user id of the current process, and that effective user id is not root the function generates a FILE ERROR 1 Not owner.