I am simulating the linux shell pipe operator, and I got stuck. The below is the minimal reproducable example of what I tried.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int do_command(char* args[])
{
    int status;
    pid_t pid = fork();

    if (pid == 0)
    {
        execvp(args[0], args);
    }
    else
    {
        wait(&status);
    }

    return 0;
}

int main() {
    int pipefd[2];
    pid_t pid;

    // Create a pipe
    if (pipe(pipefd) == -1) {
        perror("pipe");
        exit(EXIT_FAILURE);
    }

    // Redirect stdout to write end of the pipe
    if (dup2(pipefd[1], STDOUT_FILENO) == -1) {
        perror("dup2");
        exit(EXIT_FAILURE);
    }

    // the output will go to pipefd[1].
    char* echo[] = { "echo", "Hello, World!", NULL };
    do_command(echo);

    close(pipefd[1]);

    // Redirect stdin to read end of the pipe
    if (dup2(pipefd[0], STDIN_FILENO) == -1) {
        perror("dup2");
        exit(EXIT_FAILURE);
    }

    // since there is no argument to rev, it will automatically read from pipefd[0]
    char* rev[] = { "rev", NULL };
    do_command(rev);

    close(pipefd[0]);

    return 0;
}

After I run this, the program stopped without outputting any single word. I think there is something to do with close(), but I couldn’t figure it out. I did close both pipes. How can I fix it?

And is there any way to fix it without changing the structure of do_command()? I want to simulate multiple pipe chain in the future, So I want the structure of function do_command remain same, in order to call the command easily.