echo 与printf的异同

相同点：echo与printf 都是bash的内置命令

不同点：echo返回0状态，并且在标准输出输出。  

                printf可以返回不同状态，并且可以格式化输出。

Both echo and printf are Bash built-in commands. The first always exits with a 0 status, and simply prints
arguments followed by an end of line character on the standard output, while the latter allows for definition of
a formatting string and gives a non-zero exit status code upon failure.