BEGIN {OFS=FS="\t";big=999999999999999999;}#https://www.biostars.org/p/77347/
{
    if ( ($3=="exon") ) {
    split($9,format,";");
    i=0;ok=0;gn="NA";
    for (i in format){
	if (format[i] ~ /gene_id/){
	    gsub(/gene_id "/,"",format[i]);
	    gsub(/"/,"",format[i]);
	    if (substr(format[i],1,1)==" "){gi=substr(format[i],2);}else{gi=format[i]};ok++;
	}
	if (format[i] ~ /gene_name/){
	    gsub(/gene_name "/,"",format[i]);
	    gsub(/"/,"",format[i]);gn=format[i];
	}
	if (format[i] ~ /transcript_id/){
	    gsub(/transcript_id "/,"",format[i]);
	    gsub(/"/,"",format[i]);ti=format[i];ok++;
	}
    }
    if (ok==2){
	    #print format[1] "\t" format[i];
	s=$4;e=$5;st=$7;l=e-s; tlen[ti]+=l;
#	print "DBG "ti,s,e,l,tlen[ti]
	s1=big-s;
	if (s1>tmin[ti]){tmin[ti]=s1;}
	if (e>tmax[ti]){tmax[ti]=e;}
	tst[ti]=st;
	tch[ti]=$1;
	tg[ti]=gi;
	tgn[ti]=gn;	
    }
    }
}END{
    for (ti in tg){
	gi=tg[ti];
	ng[gi]++;
	gna[gi]=tgn[ti];
#	print "DBG", gi,ti,tlen[ti]
	tgl[gi]+=tlen[ti];
    }
    for (gi in ng){
	print gi,gna[gi],(1.0*tgl[gi])/ng[gi];#average transcript length
    }
 }