【关于 tr 】

不加任何选项，默认为转换操作

   例如：把小写转换成大写

# echo aaa BbB | tr '[a-z]' '[A-Z]'
AAA BBB

 

-s 把重复的字符（包括控制符）压缩成一个字符

$ cat 001.txt
And the cowwwwws went homeeeeeeeeeeeee
Or did theyyyyyyyyyyyyy

$ tr -s "[a-z]" < 001.txt
And the cows went home
Or did they

    删除空行

$ cat plane.txt
9879932 Spitfire




190992 Lancaster




238991 Typhoon

$ tr -s "[\012]" < plane.txt
9879932 Spitfire
190992 Lancaster
238991 Typhoon

-d 删除指定的字符（包括控制符）

# cat -v 001.txt
111 aaa
222 bbb
333 ccc

# tr -d '\012' < 001.txt
111 aaa222 bbb333 ccc

-c

   例如：删除只包含字母或数字的列

$ cat diary.txt
mondy 10:50
Tuesday 15:00
wednesday 15:30
thurday 10:30
Fridya 09:20

$ tr -cs "[a-z][A-Z]" "\012" mondy
Tuesday
wednesday
thurday
Fridya