[arthas@70070]$ echo 'abc' > /tmp/test.txt
[arthas@70070]$ cat /tmp/test.txt
abc

[arthas@70070]$ base64 /tmp/test.txt
YWJjCg==

$ base64 --input /tmp/test.txt --output /tmp/result.txt

$ base64 -d /tmp/result.txt
abc

$ base64 -d /tmp/result.txt --output /tmp/bbb.txt