tr命令用法

去除重复的字符
tr -s "[a-z]" < example.txt
cat example.txt | tr -s "[a-z]"

删除空行
cat example.txt | tr -s "[\n]"
cat example.txt | tr -s "[2]"

小写到大写
cat example.txt | tr "[a-z]" "[A-Z]"
cat example.txt | tr "[:lower:]" "[:upper:]"

大写到小写
与上例相反

Dos到Unix
cat example.txt | tr -s "[52]" "[2*]"
cat example.txt | tr -s "[\r2]" "[\n*]"

删除所有的tab代之以空格
cat example.txt | tr -s "[1]" "[0*]"
cat example.txt | tr -s "[\t]" "[0*]"

去除passwd的:以tab键代替增加可读性
cat /etc/passwd | tr -s "[:]" "[1]"
cat /etc/passwd | tr -s "[:]" "[\t]"