= Using an interactive shell =

undertaker starts an interactive shell, if the file to be analysed is '''-''', the default 

{{{
$ undertaker -
dead>>> ::blockpc init/main.c:370
I: Block B25 | Defect: no | Global: 0
B25
&&
( B18 <->  ! CONFIG_SMP )
&& ( B20 <->  ( B18 )  && CONFIG_X86_LOCAL_APIC )
&& ( B22 <->  ( B18 )  && ( ! (B20) )  )
&& ( B25 <-> ( ! (B18) )  )

blockpc>>> init/main.c:359
I: Block B20 | Defect: no | Global: 0
B20
&&
( B18 <->  ! CONFIG_SMP )
&& ( B20 <->  ( B18 )  && CONFIG_X86_LOCAL_APIC )
&& ( B22 <->  ( B18 )  && ( ! (B20) )  )
&& ( B25 <-> ( ! (B18) )  )

blockpc>>> 
}}}

The promt has the form "${default operation}>>>". If the input doesn't start with an '''::''' the default operation is performed for the input. If it starts with an :: it is an switch of the default operation or an model command:

|| ::dead        || new mode of operation is dead/undead analysis ||
|| ::blockpc     || block preconditions are calculated            || 
|| ::symbolpc    || symbol preconditions are calculated           ||
|| ::${mode}     || everything that can be specified with -j      ||
|| ::load <file> || loads an model file into the model database   ||
|| ::main-model  || change the main model on the fly              ||

There is an [wiki:UndertakerElDocumentation inferior mode] for the emacs operating system.