linux common problems

1.
Execute

cp -r source/* dest/

Appears -bash: /bin/cp: Argument list too long, the solution is

find ./train2017/ -name "*.jpg" | xargs -i cp {} ./images/

2.
Establish a soft connection
ln -s source dest
source refers to the location where you want to establish a soft connection
dest refers to the original storage location of the file (~/coco2017)