3、将/etc/issue文件中的内容转换为大写后保存至/tmp/issue.out文件中

3、将/etc/issue文件中的内容转换为大写后保存至/tmp/issue.out文件中
主要命令：cat /etc/issue | tr a-z A-Z >/tmp/issue.out
[root@CentOS8 /bin]#cat /etc/issue | tr a-z A-Z >/tmp/issue.out
[root@CentOS8 /bin]#cat /tmp/issue.out
\S
KERNEL \R ON AN \M