C implementation of simple shell script

task1.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h> // sleep()
#include <sys/types.h> 
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>

int make_redirection(int stream, const char* file) {
    /*  Redirects file to ctream
     *  Return value:
     *  0   success
     *  1   wrong stream specified
     *  2   can't open specified file
     *  3   loop in symbolic links encountered during filename resolution
     *  4   name is too long
     *  5   too many files open in system
     */ 

    int fd;
    
    if(stream == 0 || stream == 1 || stream == 2) {
        if(stream) {
            fd = open(file, O_WRONLY | O_CREAT | O_TRUNC, 0666);
        } else {
            fd = open(file, O_RDONLY, 0666);
        }

        if(fd == -1) {
            if(errno == EACCES) {
                return 2;
            }
        }
        dup2(fd, stream);
        close(fd);
        return 0;
    } else {
        return 1;
    }
}

int main() {
    // if ! [ -e a.txt ]
    pid_t pid = fork();
    if(pid) {
        int retval;
        waitpid(pid, &retval, 0);

        if(WIFEXITED(retval) && WEXITSTATUS(retval) == 1) {
            pid = fork();
            if(pid) {
                waitpid(pid, NULL, WNOHANG); // non-blocking call

                // sleep 1
                sleep(1);

                pid_t pid2 = fork();
                if(pid2) {
                    waitpid(pid2, NULL, 0); // waiting for backgrounded ping
                } else {
                    // tail -f a.txt
                    char* process2[] = { "tail", "-f", "a.txt", NULL };
                    execvp(process2[0], process2);
                }
            } else {
                // ping google.com > a.txt 2 > /dev/null &
                char* process3[] = { "ping", "google.com", NULL };

                make_redirection(1, "a.txt");

                make_redirection(2, "/dev/null");

                execvp(process3[0], process3);
            }
        }
    } else {
        // [ -e a.txt ]
        char* process1[] = { "[", "-e", "a.txt", "]", NULL };
        execvp(process1[0], process1);
    }

    return 0;
}