tiny shell

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/wait.h>
static const int CMD_LEN = 512;
char cmd[CMD_LEN] = "";
#define SAFE_CLOSE(fd) do { if (-1 != fd) { close(fd); fd = -1; } } while (0)
void fork_and_exec(const char *cmd, int pin, int pout) {
    pid_t pid = fork();
    if (0 == pid) {
        if (-1 != pin) {
            dup2(pin, 0);
            SAFE_CLOSE(pin);
        }
        if (-1 != pout) {
            dup2(pout, 1);
            SAFE_CLOSE(pout);
        }
        system(cmd);
        exit(0);
    }
    SAFE_CLOSE(pin);
    SAFE_CLOSE(pout);
}
int execute_cmd(char *cmd, int in) {
    int status = 0;
    char *p = cmd;
    int pipefd[2] = {0};
    while (*p) {
        switch (*p) {
        case '|':
            *p++ = 0;
            pipe(pipefd);
            fork_and_exec(cmd, in, pipefd[1]);
            execute_cmd(p, pipefd[0]);
            return 0;
            break;
        default:
            p++;
            break;
        }
    }
    fork_and_exec(cmd, in, -1);
    while (waitpid(-1, &status, WNOHANG) != -1);
    return 0;
}
char* const gets_s(char* const array, int maxlen) {
    int i;
    char c;
    for (i = 0;i < maxlen;i++) {
        c = getchar();
        if (c !='\n') {
            array[i] = c;
        }
        else {
            break;
        }
    }
    array[i]='\0';
    return array;
}
int main() {
    while (true) {
        printf ("tiny sh>>");
        gets_s(cmd, CMD_LEN - 1);
        if (0 == strcmp(cmd, "q")) {
            exit(0);
        }
        execute_cmd(cmd, -1);
    }
    
    return 0;
}