External Email - Use Caution

hello i downloaded dev version, input FREESURFER_HOME=/home/siying/sharefolder/freesurfer-linux-ubuntu18_x86_64-dev/freesurfer export SUBJECTS_DIR=/home/siying/sharefolder/freesurfer-linux-ubuntu18_x86_64-dev/freesurfer/kuang_dev/kuang_dev_results source $FREESURFER_HOME/SetUpFreeSurfer.sh then run recon-all -s ch2 -i /home/siying/sharefolder/freesurfer-linux-ubuntu18_x86_64-dev/freesurfer/kuang_dev/kuang_dev_data/ch2/ch2.nii -all –qcache -parallel

, then and appeared 'ERROR: must specify a subject id', what should i do to solve it?