michael localhost temp cat michael localhost temp echo 111 echo 333 mi

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[michael@localhost: ~/temp]
$ cat 1 3
[michael@localhost: ~/temp]
$ echo 111 >1; echo 333 >3
[michael@localhost: ~/temp]
$ cat 1 3
111
333
[michael@localhost: ~/temp]
$ echo 222 | cat 1 - 3
111
222
333
[michael@localhost: ~/temp]
$