The ifeffit() function takes 1 argument that is a character string up to 1024 characters long (including any newline characters and the like) and returns an integer. The string up to the first newline character is interpreted and run as a command by the IFEFFIT engine. After the command has been fully processed, an integer is returned, indicating a return status according to Table 9. For backwards compatibility, the function iff_exec() has identical behavior to ifeffit().