int main()

{
               FILE *fp;
               char *args[40];
               pid_t child, exited_pid;
               int status = 0;
               *args[0] = "less";
               fp = popen("ls", "r");
               child = fork();
               if(child == 0)
              {
                      dup2(fp->fd, 0);
                      if(execvp(args[0], args) == -1)
                             {
                                printf("error");
                               exit(EXIT_FAILURE);
                              }

                wait(&status);
                wait(&status);
}

typedef struct  {
       int             level;      /* fill/empty level of buffer */
       unsigned        flags;      /* File status flags          */
       char            fd;         /* File descriptor            */
       unsigned char   hold;       /* Ungetc char if no buffer   */
       int             bsize;      /* Buffer size                */
  unsigned char   *buffer;    /* Data transfer buffer       */
  unsigned char   *curp;      /* Current active pointer     */
       unsigned        istemp;     /* Temporary file indicator   */
       short           token;      /* Used for validity checking */
}       FILE;

*args[0] = "less"

args[0] = "less"