使用 dup2() 和 execve() 重定向

Question

I want to write a function void redirect(char *msg) in C that opens a file named "hello.txt" for writing, create a child process via fork(), then use output redirection (via the dup2() function) to redirect the child's standard output to your open file. Then, have the child use execve to call the "/bin/echo" program and give it the message your were passed in order to write to the file.

This is what I am having now:

void redirect(char *msg){
    int fd = fopen("hello.txt", 'wb');
    pid_t child = fork();
    if(child == 0){
        dup2(fd, STDOUT_FILENO);
        execve("/bin/echo", msg, environ);
    }
}

and it is not working, I don't know what to pass into dup2 and execve.

Answer 1

fopen returns value of type FILE * , which is not valid UNIX file descriptor. Use open for this, check out man 2 open .