Child operation with select() does not stop running after execvp() - c

Question

Running this snippet of code to experiment with piping and signals. I'm trying to learn how to properly utilize the select() function between pipes.
This process will fork. If there is something to be read from stdIn it is then written to the write end of the pipe. It is supposed to execute either a basic command entered via terminal, or it runs hard-coded commands in the code. (It's running hard code right now as "ls.")
When I run this snippet, it should quit and stop running completely when I press the letter "q" followed by ENTER, or it should quit after it runs its assigned process.
Instead, even after I hit "q" or run the process it won't stop the program completely. It is still waiting for input. It will stop running once I have hit ENTER, but it never even executes my process.
For example, if I compile and run this as "./test ls" or even just run "./test" (because ls is hard-coded in so that SHOULD just run I think), it will not run the command ls. And the program will continue to run until I've hit ENTER again.
I'm certain my rudimentary understanding of select() has to do with this issue. I'm pretty sure my select() statement needs to break at some point but I don't know what or how to check for this.
I was told that there is a method WIFEXITED() that might be able to help me but I'm just not sure how it applies in this context.
I also would like to know how to check if your pipes are empty!
I DO know that I want this to be able to both take input from the terminal and record it and also run built in functions.
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
#include <stdio.h>
int main() {
int in[2]; // parent writes; child reads
pipe(in);
if (fork() == 0) {
// instantiate the values that will be execed
char *a[2];
//a[0] = "./test3";
a[0] = "ls";
a[1] = NULL;
// redirects what is being read from stdin to the pipe
//this redirection is for a separate test that is not included
close(in[1]);
close(0);
dup(in[0]);
close(in[0]); // close read
execvp(a[0], a);
}
else {
close(in[0]); // only want parent to write
// select() params
int nfds = 3;
int check = -1;
int done = 0;
fd_set readfds;
fd_set writefds;
FD_ZERO(&readfds); // set select params
FD_SET(0, &readfds);
FD_SET(in[1], &writefds);
while ((check = select(nfds, &readfds, &writefds, NULL, NULL)) > 0) {
int size = 0;
char buf[1000];
// write to pipe for child
if (FD_ISSET(0, &readfds) && FD_ISSET(in[1], &writefds)) {
while ((size = read(0, buf, sizeof(buf))) != 0) {
write(in[1], buf, size);
}
}
// reset
FD_ZERO(&readfds);
FD_SET(0, &readfds);
FD_SET(in[1], &writefds);
}
printf("%d --------------- %d\n", (FD_ISSET(in[1], &writefds)),
FD_ISSET(0, &readfds));
}
return 0;
}
Here is the potential set of test code that can be run with the above snipped if a[0] = ./test is uncommented and a[0] = ls is commented.
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <sys/select.h>
int main () {
int fd;
char buf[11];
int ret, sret;
int flag = 0;
fd = 0;
fd_set readfds;
struct timeval timeout;
while(1) {
FD_ZERO(&readfds);
FD_SET(fd, &readfds);
timeout.tv_sec = 5;
timeout.tv_usec = 0;
sret = select(fd + 1, &readfds, NULL, NULL, NULL);
memset((void *) buf, 0, 11);
ret = read(fd, (void *) buf, 10);
flag = strcmp(buf, "q\n") == 0;
if (flag) {
return 0;
}
printf("ret = %d\n", ret);
if(ret != -1) {
printf(" buf = %s\n", buf);
}
}
return 0;
}