如何用C实现自己的基本unix shell ?

时间：2020-12-23 20:46:43

I'm a newbie to process and thread management. My Shell should understand PATH environment variable. It can be set and modified. It runs in two ways -interactive & batch mode. Shell is capable of taking more than one job like ls;ps;wc file;cal. I want to get my hands dirty on signals too. So I should handle ^K , ^c as well.

我是处理和线程管理的新手。我的Shell应该理解路径环境变量。它可以被设置和修改。它以两种方式运行——交互和批处理模式。Shell可以执行多个任务，如ls;ps;wc文件;cal。我也想把我的手弄脏信号。所以我应该处理^ K、c ^。

I know I will have to use execs, forks and pipes but just can't get started.

我知道我将不得不使用高级管理人员、餐叉和管道，但就是不能开始。

3 个解决方案

#1

14  

All the unix shells are open-source - so a good place to start may be to read the code.

所有的unix shell都是开源的——所以最好的开始是阅读代码。

If you're looking for a good starter article on the subject try Writing Your Own Shell from the Linux Gazette.

如果你想找一篇关于这个主题的好文章，试着在Linux公报上写你自己的Shell。

Another good starting point is to take a look at the source code of mini-shell just because its one of the smallest to get your head round.

另一个好的起点是看一下mini-shell的源代码，因为它是最小的代码之一。

#2

8  

Your main loop is:

你的主循环:

  • read a line (use fgets(3) for a simple shell, readline(3) for a fancy one)
  • 读一行(使用fgets(3)为一个简单的shell, readline(3)为一个花哨的)
  • parse the command
  • 解析命令
  • fork and execute the pipelines
  • 分叉并执行管道

To parse the command, there are two common choices. Write a recursive descent parser or use yacc(1) to generate one. It's a lot easier to bang out an initial parser using yacc, but you can totally get stuck debugging it and it really wants to be context-free. I prefer recursive descent but just about everyone else in the world prefers using yacc. (Technically, bison.) If the shell is really really simple, like a homework shell, yacc may be overkill.

要解析该命令，有两个常见的选项。编写递归下降解析器或使用yacc(1)生成一个递归下降解析器。使用yacc进行初始解析器会更容易，但是您完全可以调试它，而且它真的想要上下文无关。我更喜欢递归的血统，但是世界上其他的人都喜欢使用yacc。(从技术上讲,野牛。)如果shell真的很简单，比如一个家庭作业shell, yacc可能有点过头了。

To do the lexical analysis you can also roll your own or use flex.

要进行词法分析，您还可以卷自己的或使用flex。

You won't need to use any threads.

您不需要使用任何线程。

#3

4  

Many of the Unix books that describe the main system calls also implement a shell to illustrate how and why you might use the various calls. Stevens and Rochkind are two such books:

描述主系统调用的许多Unix书籍还实现了一个shell，以说明如何以及为什么使用各种调用。Stevens和Rochkind是两本这样的书:

#1

14  

All the unix shells are open-source - so a good place to start may be to read the code.

所有的unix shell都是开源的——所以最好的开始是阅读代码。

If you're looking for a good starter article on the subject try Writing Your Own Shell from the Linux Gazette.

如果你想找一篇关于这个主题的好文章，试着在Linux公报上写你自己的Shell。

Another good starting point is to take a look at the source code of mini-shell just because its one of the smallest to get your head round.

另一个好的起点是看一下mini-shell的源代码，因为它是最小的代码之一。

#2

8  

Your main loop is:

你的主循环:

  • read a line (use fgets(3) for a simple shell, readline(3) for a fancy one)
  • 读一行(使用fgets(3)为一个简单的shell, readline(3)为一个花哨的)
  • parse the command
  • 解析命令
  • fork and execute the pipelines
  • 分叉并执行管道

To parse the command, there are two common choices. Write a recursive descent parser or use yacc(1) to generate one. It's a lot easier to bang out an initial parser using yacc, but you can totally get stuck debugging it and it really wants to be context-free. I prefer recursive descent but just about everyone else in the world prefers using yacc. (Technically, bison.) If the shell is really really simple, like a homework shell, yacc may be overkill.

要解析该命令，有两个常见的选项。编写递归下降解析器或使用yacc(1)生成一个递归下降解析器。使用yacc进行初始解析器会更容易，但是您完全可以调试它，而且它真的想要上下文无关。我更喜欢递归的血统，但是世界上其他的人都喜欢使用yacc。(从技术上讲,野牛。)如果shell真的很简单，比如一个家庭作业shell, yacc可能有点过头了。

To do the lexical analysis you can also roll your own or use flex.

要进行词法分析，您还可以卷自己的或使用flex。

You won't need to use any threads.

您不需要使用任何线程。

#3

4  

Many of the Unix books that describe the main system calls also implement a shell to illustrate how and why you might use the various calls. Stevens and Rochkind are two such books:

描述主系统调用的许多Unix书籍还实现了一个shell，以说明如何以及为什么使用各种调用。Stevens和Rochkind是两本这样的书:

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