problems with redirecting stdout with execl

Question

I originally wrote a little tiny c# server that ran commands on my Linux. The app captured stdout of the command just fine and send them back to the client. Then my c# environment on the Linux box became problematic. So I decided to rewrite the app in c++ but have ran into an problems with redirecting or execl function. My first attempt I could get my redirect to work but then I issue with execl call. So I done some searching around found some code that worked, How to catch the ouput from a execl command. I did some small modification to the code to test my handling of execl call and it doesn't redirect the stdout of avrdude. I did change the function cmd_quem to handle application name and args and return error for execl. The main function call cmd_quem twice once for example command and then my command. I also have flipped the order of those two function call and every time my call to avrdude doesn't redirect the stdout but in in c# it worked.

I know that avrdude's path is correct. It seems that the arguments are getting passed thru excel either, I don't know why. The output should be an attempt to read the process not the command line options. Any help would be appreciated.

Any thoughts or suggestions?

My output for the program is

Starting RedirectPipesExe!
Usage: -c usbasp -p m8 [options]
Options:
  -p <partno>                Required. Specify AVR device.
  -b <baudrate>              Override RS-232 baud rate.
  -B <bitclock>              Specify JTAG/STK500v2 bit clock period (us).
  -C <config-file>           Specify location of configuration file.
  -c <programmer>            Specify programmer type.
  -D                         Disable auto erase for flash memory
  -i <delay>                 ISP Clock Delay [in microseconds]
  -P <port>                  Specify connection port.
  -F                         Override invalid signature check.
  -e                         Perform a chip erase.
  -O                         Perform RC oscillator calibration (see AVR053). 
  -U <memtype>:r|w|v:<filename>[:format]
                             Memory operation specification.
                             Multiple -U options are allowed, each request
                             is performed in the order specified.
  -n                         Do not write anything to the device.
  -V                         Do not verify.
  -u                         Disable safemode, default when running from a script.
  -s                         Silent safemode operation, will not ask you if
                             fuses should be changed back.
  -t                         Enter terminal mode.
  -E <exitspec>[,<exitspec>] List programmer exit specifications.
  -x <extended_param>        Pass <extended_param> to programmer.
  -y                         Count # erase cycles in EEPROM.
  -Y <number>                Initialize erase cycle # in EEPROM.
  -v                         Verbose output. -v -v for more.
  -q                         Quell progress output. -q -q for less.
  -l logfile                 Use logfile rather than stderr for diagnostics.
  -?                         Display this usage.

avrdude version 6.3-20171130, URL: <http://savannah.nongnu.org/projects/avrdude/>
No data received.
Child exit status = 0
Data from who command: pi       tty7         2020-07-22 19:25 (:0)

Child exit status = 0
End RedirectPipesExe!

I have tested the code on Gentoo and raspberry pi box. The raspberry has a functional programmer hooked up and it is the same output.

int cmd_quem(const char *pApp, const char *pArgs) {
  int result;
  int pipefd[2];
  FILE *cmd_output;
  char buf[1024];
  int status;

  result = pipe(pipefd);
  if (result < 0) {
    perror("pipe");
    exit(-1);
  }

  result = fork();
  if (result < 0) {
    exit(-1);
  }

  if (result == 0) {
    dup2(pipefd[1], STDOUT_FILENO); /* Duplicate writing end to stdout */
    close(pipefd[0]);
    //close(pipefd[1]);

    //execl("/usr/bin/who", "who", NULL);
    int r = execl(pApp, pArgs, NULL);
    printf("Error returned by excel: %d\n", r);
    _exit(1);
  } 
  /* Parent process */
  close(pipefd[1]); /* Close writing end of pipe */

  cmd_output = fdopen(pipefd[0], "r");

  if (fgets(buf, sizeof buf, cmd_output)) {
    printf("Data from who command: %s\n", buf);
  } else {
    printf("No data received.\n");
  }

  wait(&status);
  printf("Child exit status = %d\n", status);

  return 0;
}

int main() {
  printf("Starting RedirectPipesExe!\n");
  cmd_quem("/usr/bin/avrdude", "-c usbasp -p m8");
  cmd_quem("/usr/bin/who", "who" ); 
  printf("End RedirectPipesExe!\n");
  return 0;
}