When I using pipes to display file content as the following code, I expect, when I comment the wait command (in the last part of parent process), I don’t see parent process in ps command’s output, but I see both parent and child process in the output.

the following code shows argv1 content. after compile and make exec file (for example xpager) it should be executed as xpager filename.

platform is Ubuntu 22.04.4 LTS

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/wait.h>

#define BUFSIZE 8192
#define PPAGER  "/usr/bin/less"

int main(int argc, char *argv[]) {
    pid_t   pid;
    int eerrno, n;
    int in, pfd[2];
    char    buf[BUFSIZE];
    char    *pager, *argv0;


    if (argc != 2) {
        printf("usage: %s <pathname>n", argv[0]);
        exit(1);
    }

    if ( (in = open(argv[1], O_RDONLY)) < 0) {
        eerrno = errno;
        printf("Open error. %s(%d)n", strerror(errno), errno);
        exit(eerrno);
    }

    if ( pipe(pfd) < 0) {
        eerrno = errno;
        printf("pipe error. %s(%d)n", strerror(errno), errno);
        exit(eerrno);
    }


    pid = fork();
    switch (pid) {
        case -1:
            eerrno = errno;
            printf("fork error. %s(%d)n", strerror(errno), errno);
            exit(eerrno);

        case 0:
            close(pfd[1]);
            close(in);
            if (STDIN_FILENO != pfd[0]) {
                if (dup2(pfd[0], STDIN_FILENO) < 0) {
                    eerrno = errno;
                    printf("dup2 error. %s(%d)n", strerror(errno), errno);
                    exit(eerrno);
                }
                close(pfd[0]);
            }
            if ((pager=getenv("PPAGER")) == NULL)
                pager = PPAGER;
            if ((argv0=strrchr(pager, '/')) != NULL)
                argv0++;
            else
                argv0=pager; 
            execlp(pager, argv0, argv[1], (char *)0);
        default:
            close(pfd[0]);
            while((n=read(in, buf, BUFSIZE)) > 0) {
                if (write(pfd[1], buf, n) < 0) {
                    eerrno = errno;
                    printf("write errno. %s(%d)n", strerror(errno), errno);
                    kill (pid, 9);
                    exit(eerrno);
                }
            }
            if (n < 0) {
                eerrno = errno;
                printf("read error. %s(%d)n", strerror(errno), errno);
                kill(pid, 9);
                exit(eerrno);
            }
            close(pfd[1]);
        //  wait(NULL);
    }

    exit(0);
}