piping and redirection for execv command

Question

Why piping doesn't work for the following code?

int p_fds[2];
pipe(p_fds);

int pid_left = fork();
if (pid_left == 0){
    dup2(p_fds[1],STDOUT_FILENO);
    close(p_fds[0]);
    close(p_fds[1]);
    execv("cat", (char*[]){ "cat", "afile" });//execlp("cat", "cat", "afile", NULL);         
    exit(1);
}

int pid_right = fork();
if (pid_right == 0){
    dup2(p_fds[0], STDIN_FILENO);
    close(p_fds[1]);
    close(p_fds[0]);
    execv("grep", (char*[]){ "grep", "something" });//execlp("grep", "grep", "something", NULL);
    exit(1);
}

close(p_fds[0]);
close(p_fds[1]);
waitpid(pid_left, NULL, 0);
waitpid(pid_right, NULL, 0);

but it works with execlp or any other exec* except execv. What should be updated to make it work with execv? It is expected that this code print something in main stdout like cat afile | grep sth.

Answer 1

It is needed to provide full path for execv(full_path, char *const argv[]); execv("/bin/cat") Other functions (exec*) perforce search in $PATH