Here is a simple tail (without the -f) written in IOS Tcl by one of our Tcl developers (not me).
proc tail { show_cmd { n 10 } } {
set eol "\n"
if {[catch {set show_out [exec $show_cmd]}]} {
puts $fd
return
} else {
set data [split $show_out $eol]
}
for {set i [expr {[llength $data]-($n+1)}]} \
{$i<=[expr {[llength $data]-2}]} {incr i} {
puts [lindex $data $i]
}
}
You could adapt it for tail -f by calling the desired command periodically, checking the size of the output, and printing out the new data after the last size checkpoint. The liveliness of the updates would depend on how often you run the command. The more often you run the command, the more CPU impact you'll have.
This script requires IOS 12.3(2)T, but probably could be adapted to run on CatOS 8.x which has its own Tcl interpreter (though a much older version with some changes).
