执行与我的C程序不同的程序

Question

I am writing a basic shell in Linux as a hobby, I want to start working on program execution, but have no idea on how to do this. I have seen execp() and its various brothers and sisters, but apparently that forces the kernel to drop the currently running process, in this case my shell, and continue with the new process.

So basically all I need is a function that I can use to call a command such as ls or cd have it execute and then return to my shell.

All help is appreciated.

Answer 1

ouah's answer is essentially correct, but it won't work for cd . Your shell needs to implement that as a builtin command (ie the shell needs to contain the code for cd .

The reason for this is that fork first creates a new copy of the current process (the running instance of the shell, in this case). Then exec overwrites the new process with the executable you want to run. When the command finishes, the new process terminates and goes away. If you use this for cd it will change the working directory of the new process but leave the working directory of the old process (the shell) totally untouched.

Answer 2

使用fork创建一个新进程，然后调用exec 。

Answer 3

Use something like this:

if (fork ()==0) {
    execl ("/bin/sh",NULL);
}

This will create the new process (an exact copy of already running one), then replace it with the new one. Please note this might require some workarounds in some environments where CPU does not fully support virtual memory, and your original process is so big that you can not duplicate it.