CODEWITHSUNDEEP
cunix
Tommy K
Tommy K

Reputation: 1807

writing a program to act like command line in C

So from what I found out on my own I know I'm going to need to use fork() and execvp(), but I can't quite figure out how to use execvp() correctly from any examples online. Its supposed to let me essentially run command line stuff, but I don't understand the arguments it takes. Like if I wanted to run ls -a how would I put that into execvp()? And then there's the problem of exec() doesn't return. How do I handle that?

Upvotes: 0

Views: 215

Answers (1)

Spudd86
Spudd86

Reputation: 3006

First, exec() doesn't return because it results in the process having it executing program replaced with whatever program was exec()ed. That is if you run ls via exec() after a fork() the PID of ls will be the same as the one that called exec(). That is exec() doesn't create a new process so it can't return because all the memory and code from the program that called it is effectively gone and replaced with whatever it exec()ed

Run ls -a with execvp() assuming ls is in /bin

const char *file = "/bin/ls";
const char *arg1 = "ls";
const char *arg2 = "-a";
const char **argv = {arg1, arg2, NULL};
execvp(file, argv);

Upvotes: 3

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