说明：  UNIX/Linux shell 有很多种，比如 Bourne shell(又称 AT&T shell,标准的 UNIX shell, sh)、 C shell(又称 Berkeley shell)、 Korn shell(Bourne shell 的扩展集,ksh)、 TC shell、 Z shell、 Bash shell 等。 这些 shell 的功能和使用都不尽相同。我们通常说 shell 编程，其实说精通所有 shell 编 程是很难的， 一般也没有必要。 学习 shell 编程最好选定一种 shell 来学习。 而如此众多的 shell 选那一种比较好呢？笔者的意见是选择 Bash，这不仅因为 Bash 几乎可以说是所有 shell 中 功能最丰富的，也符合 IEEE 1003.2 POSIX/ISO 9945.2 Shell 和工具部分规范，同时 Bash 也 是 Linux 上的默认 shell。
(UNIX/Linux shell there are many, such as the Bourne shell (known as AT & T shell, the standard UNIX shell, sh), C shell (also known as the Berkeley shell), Korn shell (Bourne shell extension set, ksh), TC shell, Z shell, Bash shell and so on. Function and use the shell are different. We usually say shell programming, in fact, that it is difficult to master all shell programming, generally it is not necessary. Learning shell programming shell preferably choose one to learn. And so many shell choose what kind of situation? The author' s view is to Bash, not only because the Bash shell can be said almost all the most feature-rich, but also in line with IEEE 1003.2 POSIX/ISO 9945.2 Shell and Tools section of the specification, while Bash is the default shell Linux on.)