korn 和 bash shell 的区别
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Difference between korn and bash shell
提问by Programmer
I am completely new to Unix. Presently, I have been asked to learn about both KornShell (ksh)and Bash shell. Can some one please give me a short overview about the two?
我对 Unix 完全陌生。目前，我被要求学习KornShell (ksh)和Bash shell。有人可以给我一个关于这两个的简短概述吗？
Is the term "shell" synonymous to "terminal"?
术语“ shell”是“终端”的同义词吗？
I understand that I can read documents about both online. But I believe that an overview from an experienced Unix programmer will help me better understand.
我知道我可以在线阅读有关两者的文档。但我相信一位经验丰富的 Unix 程序员的概述将帮助我更好地理解。
回答by SriniV
Post from UNIX.COM
来自 UNIX.COM 的帖子
Shell features
外壳功能
This table below lists most features that I think would make you choose one shell over another. It is not intended to be a definitive list and does not include every single possible feature for every single possible shell. A feature is only considered to be in a shell if in the version that comes with the operating system, or if it is available as compiled directly from the standard distribution. In particular the C shell specified below is that available on SUNOS 4.*, a considerable number of vendors now ship either tcsh or their own enhanced C shell instead (they don't always make it obvious that they are shipping tcsh.
下表列出了我认为会让您选择一种外壳而不是另一种外壳的大多数功能。它不是一个明确的列表，也不包括每个可能的 shell 的每个可能的功能。只有在操作系统随附的版本中，或者如果直接从标准发行版编译可用，则功能才被视为在 shell 中。特别是下面指定的 C shell 在 SUNOS 4.* 上可用，相当多的供应商现在提供 tcsh 或他们自己的增强型 C shell（他们并不总是明确表示他们正在提供 tcsh。
Code:
代码：
sh csh ksh bash tcsh zsh rc es
Job control N Y Y Y Y Y N N
Aliases N Y Y Y Y Y N N
Shell functions Y(1) N Y Y N Y Y Y
"Sensible" Input/Output redirection Y N Y Y N Y Y Y
Directory stack N Y Y Y Y Y F F
Command history N Y Y Y Y Y L L
Command line editing N N Y Y Y Y L L
Vi Command line editing N N Y Y Y(3) Y L L
Emacs Command line editing N N Y Y Y Y L L
Rebindable Command line editing N N N Y Y Y L L
User name look up N Y Y Y Y Y L L
Login/Logout watching N N N N Y Y F F
Filename completion N Y(1) Y Y Y Y L L
Username completion N Y(2) Y Y Y Y L L
Hostname completion N Y(2) Y Y Y Y L L
History completion N N N Y Y Y L L
Fully programmable Completion N N N N Y Y N N
Mh Mailbox completion N N N N(4) N(6) N(6) N N
Co Processes N N Y N N Y N N
Builtin artithmetic evaluation N Y Y Y Y Y N N
Can follow symbolic links invisibly N N Y Y Y Y N N
Periodic command execution N N N N Y Y N N
Custom Prompt (easily) N N Y Y Y Y Y Y
Sun Keyboard Hack N N N N N Y N N
Spelling Correction N N N N Y Y N N
Process Substitution N N N Y(2) N Y Y Y
Underlying Syntax sh csh sh sh csh sh rc rc
Freely Available N N N(5) Y Y Y Y Y
Checks Mailbox N Y Y Y Y Y F F
Tty Sanity Checking N N N N Y Y N N
Can cope with large argument lists Y N Y Y Y Y Y Y
Has non-interactive startup file N Y Y(7) Y(7) Y Y N N
Has non-login startup file N Y Y(7) Y Y Y N N
Can avoid user startup files N Y N Y N Y Y Y
Can specify startup file N N Y Y N N N N
Low level command redefinition N N N N N N N Y
Has anonymous functions N N N N N N Y Y
List Variables N Y Y N Y Y Y Y
Full signal trap handling Y N Y Y N Y Y Y
File no clobber ability N Y Y Y Y Y N F
Local variables N N Y Y N Y Y Y
Lexically scoped variables N N N N N N N Y
Exceptions N N N N N N N Y
Key to the table above.
上表的关键。
Y Feature can be done using this shell.
Y 功能可以使用此外壳完成。
N Feature is not present in the shell.
N 特征不存在于外壳中。
F Feature can only be done by using the shells function mechanism.
F Feature 只能通过使用shells 函数机制来完成。
L The readline library must be linked into the shell to enable this Feature.
L readline 库必须链接到shell 才能启用此功能。
Notes to the table above
上表注意事项
1. This feature was not in the original version, but has since become
almost standard.
2. This feature is fairly new and so is often not found on many
versions of the shell, it is gradually making its way into
standard distribution.
3. The Vi emulation of this shell is thought by many to be
incomplete.
4. This feature is not standard but unofficial patches exist to
perform this.
5. A version called 'pdksh' is freely available, but does not have
the full functionality of the AT&T version.
6. This can be done via the shells programmable completion mechanism.
7. Only by specifying a file via the ENV environment variable.
回答by sTg
There are open source versions of ksh. You can run it on Linux. There was an older ksh for OSS called pdksh that acted somewhat differently than the newer ksh and that may be why folks didn't like it.
ksh 有开源版本。你可以在 Linux 上运行它。用于 OSS 的旧 ksh 称为 pdksh，其行为与较新的 ksh 略有不同，这可能就是人们不喜欢它的原因。
There are several differences - bash has most of what ksh does and then some extra stuff. A script written to run in ksh would likely run in bash just fine. A lot of the differences deal with math, variables, arrays, functions etc... - bash just seems to have a hell of lot more of this than ksh
有几个不同之处 - bash 具有 ksh 的大部分功能，然后还有一些额外的东西。编写在 ksh 中运行的脚本很可能在 bash 中运行得很好。许多差异涉及数学、变量、数组、函数等...... - bash 似乎比 ksh 多得多
ksh is available on multiple platforms by default but bash would have to be specifically added. On the flip side though, most Linux distros come with bash and you have to add ksh if you want it.
The vi style editing that ksh used by default but not bash. However, you can type "set -o vi" in bash to get that same functionality.
ksh 默认使用的 vi 样式编辑，但不使用 bash。但是，您可以在 bash 中键入“set -o vi”以获得相同的功能。
one reason for using ksh for scripting is, this shell is available on nearly all existing flavours of *nix. Bash is not installed by default on all *nix.
