Return the value of the Tcl variable DERVISH_HISTFILE. If the variable is not set, return the value /dev/null.
Read the file defined by the Tcl variable DERVISH_HISTFILE and add each line read to the current history list. These commands are not executed before being added to the list. The file must be sourced in order to execute the commands.
Save the current history list to the file defined by the Tcl variable DERVISH_HISTFILE. Each line in the history list is written to the file minus the number indicating its position in the list. For example the following history list -