参考：https://medium.com/analytics-vidhya/simple-tutorial-to-install-use-gnu-parallel-79251120d618

Download Latest version of GNU Parallel

$ wget http://ftp.gnu.org/gnu/parallel/parallel-latest.tar.bz2

Unzip it, it creates a new folder parallel-yyyymmdd

$ sudo tar xjf parallel-latest.tar.bz2

Change to new folder

$ cd parallel-yyyymmdd

Build the software in your machine

$ sudo ./configure && make

若无管理员权限，则指定prefix=自己的文件夹

Install it

$ sudo make install

Switch to home directory

$ cd

How to Test Parallel ?

$ parallel



使用：
ls [input dir] | parallel --jobs 32 --eta tesseract [input dir]/{} [output dir]{.} --oem 1 hocr (可选--tmpdir=[temp dir])