Linux命令 - 去掉空格、去掉多余空格、大小写转换、打印列

1.空格
⑴去掉空格

leon@netview:~$ date
Fri Sep 30 14:30:55 CST 2016

leon@netview:~$ date | sed s/[[:space:]]//g
FriSep3014:31:50CST2016

⑵去掉多余空格

leon@netview:~$ echo "hello    world" | tr -s [:space:]
hello world 

2.大小写
⑴ tr a-z A-Z

leon@netview:~$ echo ABCdef | tr a-z A-Z
ABCDEF

⑵ tr [:lower:] [:upper:]

leon@netview:~$ echo ABCdef | tr [:lower:]  [:upper:] 
ABCDEF

3.打印列

leon@netview:~$ echo AAA BBB CCC DDD | awk '{print $2}'
BBB

4.组合

cp main_app.log main_app_`date | awk '{print $4}'`.log

main_app_14:40:25.log