#cat test.csv
chinausajapanfucknow
#head -2 test.csv （输出前两行）chinausa
#tail -2 test.csv （输出最后两行）fucknow
#tac test.csv (按列反序输出 常用于查看日志)nowfuckjapanusachina
#rev test.csv （按行反序输出）anihcasunapajkcufwon