FeynCalcForm[expr] changes the printed output to a an easy-to-read form. It allows a readable output also when running a terminal based Mathematica session. Whether the result of FeynCalcForm[expr] is displayed or not, depends on the setting of $PrePrint.
$PrePrint = FeynCalcForm forces displaying everything after applying FeynCalcForm. In order to change to the normal (internal) Mathematica OutputForm, do: $PrePrint=..
Overview, FC, FeynCalcExternal, FeynCalcInternal.
This is the normal notebook display:
SUNTrace[SUNT[a] . SUNT[b] . SUNT[c]]\text{tr}(T^a.T^b.T^c)
This is the shorthand (terminal) display (easy-to-read form):
$PrePrint = FeynCalcForm;
SetOptions[$FrontEndSession, Evaluate[(Options[$FrontEndSession, "CommonDefaultFormatTypes"] /. ("Output" -> _) -> ("Output" ->OutputForm))[[1]]]];
SUNTrace[SUNT[a] . SUNT[b] . SUNT[c]]\text{tr}(T^a.T^b.T^c)
Reset to normal notebook display:
$PrePrint =.;
SetOptions[$FrontEndSession, Evaluate[(Options[$FrontEndSession, "CommonDefaultFormatTypes"] /. ("Output" -> _) -> ("Output" ->TraditionalForm))[[1]]]];
SUNTrace[SUNT[a] . SUNT[b] . SUNT[c]]\text{tr}(T^a.T^b.T^c)