calling execve() + changing PWD

Question

I want to write a program A which executes another program B . It is very important to execute program B from it's directory, cause it turns on program BB who sits in the same directory of B .

I mean: ./B will work

./b/B won't work

I thought about two ways to do so:

1. do fork() , change the PWD in env, and then call execv()
2. do fork() , create a temporal variable, envp , and call execve()

Lets say program A sits here: /home/a , and program B and BB sits here: /home/a/b

This is my code of program A who sits in /home/a

#include <iostream>
#include <errno.h>

int main() {

    int pid;
    char *cmd[20] = {"/home/a/b/B", NULL};

    if ((pid = fork()) == 0) {

        /*if (putenv("PWD=/home/a/b") < 0) {
            fprintf(stderr, "error PWD%s\n", strerror(errno));
        }*/

        char *envp[20] = {"PWD=/home/a/b", NULL};

        execve( cmd[0], cmd, envp);

        fprintf(stderr, "error: execv: %s\n", strerror(errno));
        exit(0);
    } else if (pid < 0) {
        fprintf(stderr, "error: fork: %s\n", strerror(errno));
        exit(0);
        }

    fprintf(stderr, "father quits\n");

return 0; }

I tried both of my solutions, but none of them worked, I mean, I manage to execute program B , but it can't find program BB . I also printed program's B 's PWD, and it's /home/a/b/ - but still, it cannot execute BB .

Is it possible? Can someone see what I am I do wrong?

Thanks

Answer 1

您正在寻找chdir()而不是envp操作。