V|||. Creating out put files for Xgraph $traffic set packet-size $size $traffic set burst-time $burst $traffic set idle-time $idle $traffic set rate $rate should be: $traffic set packetSize_ $size $traffic set burst_time_ $burst $traffic set idle_time_ $idle $traffic set rate_ $rate Maybe the previous code is old usage? Anyway it didn't give me the right output. Xiaobing