The alog command reads standard input and writes it to the specified logfile. If the file does not already exist it is created with a default size of 10240 bytes. The size can be specified via the -size <size> option. The -a option is used to append to the file.
The typical use of this command is to capture the output from a server so that it can be recorded without the output filling up the disk by writing to a conventional logfile that just grows and grows.