linux从一个文件夹内移动指定个数文件到另一文件夹

# move n files from dir1 to dir2
ls -Q dir1 | head -n | xargs -i mv dir1/{} dir2/

例子：

$ tree -d
.
├── annotations
├── train  #40,000items
└── val    #0items

# move 2400 files from train to val
$ ls -Q ./train/ | head -2400 | xargs -i mv train/{} val/

$ tree -d
.
├── annotations
├── train  #37,600items
└── val    #2,400items