如何向bash添加内部命令？

这实际上是作为 a more specific question的答案的一部分(如何将评估的PS1输出变为变量),我认为该过程值得自己提出问题和答案,一个更广泛的修改bash源代码的过程.

以下是添加内部命令evalps1的步骤,该命令旨在为您提供与主提示字符串相同的输出.它基于4.2版代码库.

步骤1.

首先,更改support / mkversion.sh,这样你就不会将它与“真正的”bash混淆,以便FSF可以为保修目的拒绝所有知识:-)只需更改一行(我添加了-pax位) ：

echo "#define DISTVERSION "${float_dist}-pax""

该脚本是创建version.h的脚本,并影响从bash获取版本信息的各种方法： – version,$BASH_VERSION变量等等.

第2步：

更改builtins / Makefile.in以添加新的源文件.这需要许多步骤.

(a)将$(srcdir)/evalps1.def添加到DEFSRC的末尾.此def文件包含有关内部命令以及实现代码的信息.

(b)将evalps1.o添加到OFILES的末尾.这只会导致您的代码与bash链接.

(c)添加所需的依赖项：

evalps1.o: evalps1.def $(topdir)/bashtypes.h $(topdir)/config.h 
           $(topdir)/bashintl.h $(topdir)/shell.h common.h

第3步：

添加builtins / evalps1.def文件本身,这是运行evalps1命令时执行的代码：

This file is evalps1.def,from which is created evalps1.c.
It implements the builtin "evalps1" in Bash.

Copyright (C) 1987-2009 Free Software Foundation,Inc.

This file is part of GNU Bash,the Bourne Again SHell.

Bash is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation,either version 3 of the License,or
(at your option) any later version.

Bash is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Bash.  If not,see <http://www.gnu.org/licenses/>.

$PRODUCES evalps1.c

$BUILTIN evalps1
$FUNCTION evalps1_builtin
$SHORT_DOC evalps1
Outputs the fully interpreted PS1 prompt.

Outputs the PS1 prompt,fully evaluated,for whatever nefarious purposes
you require.
$END

它的大部分是GPL许可证(因为我从exit.def修改它),如上所示,最后使用一个非常简单的函数来获取和解码PS1,使用与shell本身使用相同的函数：

#include <config.h>
#include "../bashtypes.h"
#include <stdio.h>
#include "../bashintl.h"
#include "../shell.h"
#include "common.h"

int
evalps1_builtin (list)
     WORD_LIST *list;
{
  char *ps1 = get_string_value ("PS1");
  if (ps1 != 0)
  {
    ps1 = decode_prompt_string (ps1);
    if (ps1 != 0)
    {
      printf ("%s",ps1);
    }
  }
  return 0;
}

在这种情况下,代码本身非常简单,虽然它使用了我认为不必要的复杂缩进/支撑规则和K& R风格的预原型函数声明 – 我保持它们与当前代码保持一致以保持一致性.

代码只是调用函数来获取PS1环境变量,然后调用另一个解码提示字符串的函数.最后,它将解码后的字符串输出到标准输出.

当然,您可以使用自己的代码替换该代码(以及将命令和文件名从evalps1更改为其他内容),具体取决于您的特定需求.

第4步：

只需在顶级目录中构建东西：

./configure
make

出现在该顶级目录中的bash可执行文件可以重命名为paxsh(例如),但我怀疑它将变得像它的祖先一样普遍:-)

运行它,你可以看到它在行动中,从一个真正的bash shell开始：

pax> mv bash paxsh

pax> ./paxsh --version
GNU bash,version 4.2-pax.0(1)-release (i686-pc-linux-gnu)
Copyright (C) 2011 Free Software Foundation,Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY,to the extent permitted by law.

pax> ./paxsh

pax> echo $BASH_VERSION
4.2-pax.0(1)-release

pax> echo "[$PS1]"
[pax> ]

pax> echo "[$(evalps1)]"
[pax> ]

pax> PS1="h: "

paxbox01: echo "[$PS1]"
[h: ]

paxbox01: echo "[$(evalps1)]"
[paxbox01: ]