如何在自己的shell中实现自己的cd命令 [英] How to implement your own cd command in your own shell

问题描述

我正在做一个小型项目:我自己的命令解释器(外壳)"，例如Bash外壳程序或Sh外壳程序.到现在为止，它可以执行每个预定义的命令，例如ls，ps，pwd，date.除此之外，我还实现了其他一些操作，例如Input Redirection(<)，Output Redirection(>)，PIPE(|)功能.与此同时，我实现了自己的用户命令，例如pid，ppid，quit，hist.

I am working in a mini project: "MY OWN COMMAND INTERPRETER (SHELL)", like the Bash shell or Sh shell. Till now it can execute every predefined commands like ls, ps, pwd, date. Except this I have implemented some other operations like Input Redirection(<), output redirection(>), PIPE (|) features. Along with this i have implemented my own user-commands like pid, ppid, quit, hist.

vvdnlt208@vvdnlt208-Vostro-3446:~/project/Vector/sourabh/unix/proj2$ ./my_sh  
<1 SOURABH> ls
 a     cd.c       execute.o  inredir.c  main.o   multiexec.o  my_sh   sh.c                sigign.c  test.c
addhist.c  dir        header.h   inredir.o  Makefile     mypipe.c     outredir.c  showhist.c  sigign.o  tetest.c
addhist.o  execute.c  inredir    main.c     multiexec.c  mypipe.o     outredir.o    showhist.o  test2.c
<2 SOURABH> ps
PID TTY          TIME CMD
6120 pts/10   00:00:01 bash
6510 pts/10   00:00:00 grep
6512 pts/10   00:00:00 grep
6514 pts/10   00:00:00 grep
6516 pts/10   00:00:00 grep
7772 pts/10   00:00:00 my_sh
7774 pts/10   00:00:00 ps
<3 SOURABH> pwd
/home/vvdnlt208/project/Vector/sourabh/unix/proj2
<4 SOURABH> date
Fri Nov 14 16:44:24 IST 2014
<5 SOURABH> 
<6 SOURABH> 
<7 SOURABH> 
<8 SOURABH> hist
1 ls
2 ps
3 pwd
4 date
8 hist
<9 SOURABH> ls >a.txt
<10 SOURABH> pid
7772
<11 SOURABH> ppid

但是我在执行cd命令时遇到了一些困难...

But I am facing some difficulty in executing the cd command...

<12 SOURABH> cd
cd: No such file or directory
<13 SOURABH> cd dir
cd: No such file or directory
<14 SOURABH> 

有人告诉我自己实现它...请帮助我这样做.预先感谢.

Someone told me to implement it by my own... Please help me in doing this. Thanks in advance.

推荐答案

cd不是程序，它是内置命令.内置命令直接内置到外壳中.

cd is not a program, it's a built-in command. The built-in command are directly built into the shell.

要实现cd，您基本上需要

1. 使用chdir()更改当前目录
2. 更新一些环境变量(例如Klas Lindback所说的:OLDPWD和PWD)

1. Use chdir() to change the current directory
2. Update some environment variables (like Klas Lindback said: OLDPWD and PWD)

这篇关于如何在自己的shell中实现自己的cd命令的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！