关于 shell 和版本的话题，再加点料...很好玩的：
关于双中括号的问题 - FreeBSD China :
https://www.freebsdchina.org/forum/viewtopic.php?t=56452「
loader:
文章发表于: Mon 2013-01-21 21:54:20 发表主题: 引用并回复
door10000 写到:
看来openbsd和freebsd的默认sh都不相同的。。
欢迎你来地球玩...
等我开始用 OpenBSD 的时候已经是默认 ksh 了
原来曾经有过 NetBSD 的 ash
引用:
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revision 1.9
date: 1997/08/20 23:43:47; author: deraadt; state: dead; lines: +1 -1
this has not been used for a while
----------------------------
revision 1.8
date: 1997/01/05 08:17:31; author: deraadt; state: Exp; lines: +2 -2
HOSTCC; from rahnds
----------------------------
revision 1.7
date: 1996/10/20 00:54:41; author: millert; state: Exp; lines: +4 -4
Sync with NetBSD. Adds better POSIX compliance amongst others.
----------------------------
revision 1.6
date: 1996/10/12 01:12:02; author: deraadt; state: Exp; lines: +2 -2
use HOSTCC; from dale
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revision 1.5
date: 1996/09/16 10:51:33; author: downsj; state: Exp; lines: +3 -1
These should always be static.
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revision 1.4
date: 1996/06/23 14:21:05; author: deraadt; state: Exp; lines: +1 -1
update rcsid
----------------------------
revision 1.3
date: 1996/03/03 12:32:57; author: niklas; state: Exp; lines: +6 -9
From NetBSD:
Fix problems with the way init.o is built:
* Prevent gratuitous rebuilds when nothing has changed.
* Make sure it is rebuilt if a .h file is updated.
----------------------------
revision 1.2
date: 1995/12/14 01:22:27; author: deraadt; state: Exp; lines: +6 -1
update from netbsd, including:
Fix PR/1760, where 'cd -' before any other command could cause a reference
to an uninitialized pointer. Use getcwd() to get the current working directory,
instead of forking /bin/pwd [per Scott's suggestion]
----------------------------
revision 1.1
date: 1995/10/18 08:37:21; author: deraadt; state: Exp;
branches: 1.1.1;
Initial revision
----------------------------
revision 1.1.1.1
date: 1995/10/18 08:37:21; author: deraadt; state: Exp; lines: +0 -0
initial import of NetBSD tree
」
Bash这门UNIX下的壳语言 - FreeBSD China :
https://www.freebsdchina.org/forum/viewtopic.php?t=58262若看完精分/精分加重，那么恭喜了，嗯，不用谢！