a problem when train

[ESCEBT]

sorry, I have a question ;
when i run './experiments/scripts/train_faster_rcnn.sh 1 coco res101 ' in terminal to begin train,
it failed and showed this:

• set -e
• export PYTHONUNBUFFERED=True
• PYTHONUNBUFFERED=True
• GPU_ID=1
• DATASET=coco
• NET=res101
• array=($@)
• len=3
• EXTRA_ARGS=
• EXTRA_ARGS_SLUG=
• case ${DATASET} in
• TRAIN_IMDB=coco_2014_train+coco_2014_valminusminival
• TEST_IMDB=coco_2014_minival
• STEPSIZE='[350000]'
• ITERS=490000
• ANCHORS='[4,8,16,32]'
• RATIOS='[0.5,1,2]'
  ++ date +%Y-%m-%d_%H-%M-%S
• LOG=experiments/logs/res101_coco_2014_train+coco_2014_valminusminival__res101.txt.2019-12-07_14-25-03
• exec
  ++ tee -a experiments/logs/res101_coco_2014_train+coco_2014_valminusminival__res101.txt.2019-12-07_14-25-03
  ./experiments/scripts/train_faster_rcnn.sh: line 49: tee: command not found

it means the tee not found ,i cannot understand ,please help me, thx~