测试数据：
[weblogic@etp-mall-dev7][/tmp]$ cat msn.txt
aaa bbb
bbb ccc
ccc ddd
bbb eee
aaa ccc
bbb sss
转换大小写：
eg.1:
[xiluhua@vm-xiluhua][~]$ cat msn.txt | tr a-z A-Z
eg.2:
AAA BBB BBB CCC CCC DDD BBB EEE AAA CCC BBB SSS
用tr命令转换一个文件的内容，并将转换的结果输出到另一个文件
eg.1: [xiluhua@vm-xiluhua][~]$ cat msn.txt | tr [:lower:] [:upper:] > msn.bk eg.2: [xiluhua@vm-xiluhua][~]$ tr [:lower:] [:upper:] < msn.txt > msn3.bk [xiluhua@vm-xiluhua][~]$ cat msn3.bk AAA BBB BBB CCC CCC DDD BBB EEE AAA CCC BBB SSS