automate xinu console tools for great workflow good

cursed_runner.c

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

#define READ 0
#define WRITE 1

int main() {
    printf("start\n");
    int writer[2];
    int reader[2];

    if (pipe(writer) < 0) {
        fprintf(stderr, "error: writer pipe: %s\n", strerror(errno));
        return EXIT_FAILURE;
    }

    if (pipe(reader) < 0) {
        close(writer[READ]); close(writer[WRITE]);
        fprintf(stderr, "error: reader pipe: %s\n", strerror(errno));
        return EXIT_FAILURE;
    }
    printf("pipes made\n");
    pid_t pid = fork();
    if (pid == 0) {
        // child proc

        // duplicate read end of the writer pipe onto stdin (so parent can write to child's stdin)
        if (dup2(writer[READ], STDIN_FILENO) < 0) {
            fprintf(stderr, "error: writer dup2: %s\n", strerror(errno));
            exit(EXIT_FAILURE);
        }
        
        // duplicate write end of the reader pipe onto stdout and stderr (so parent can read child's stdout/err)
        if (dup2(reader[WRITE], STDOUT_FILENO) < 0) {
            fprintf(stderr, "error: reader dup2 (stdin): %s\n", strerror(errno));
            exit(EXIT_FAILURE);
        }
        if (dup2(reader[WRITE], STDERR_FILENO) < 0) {
            fprintf(stderr, "error: reader dup2 (stderr): %s\n", strerror(errno));
            exit(EXIT_FAILURE);
        }

        // close unused pipes (dup2 silently closes some of these so we have a couple no-ops. nbd)
        close(writer[READ]); close(writer[WRITE]);
        close(reader[READ]); close(writer[WRITE]);
        
        // 
        char* args[] = {"/p/xinu/bin/cs-console", "-c", "quark", NULL};
        char* env[] = {"CS_FILENAME=/homes/brookea/cs/cs354/xinu-spring2020/compile/xinu.xbin", NULL};
        exit(execve(args[0], args, env));
    } else if (pid > 0) {
        printf("parent\n");
        // parent proc
        
        // close unneeded pipe ends
        close(writer[READ]);
        close(reader[WRITE]);

        // send our cursed input to the child
        dprintf(writer[WRITE], "%cd", '\0');
        sleep(1);
        dprintf(writer[WRITE], "\n");
        sleep(1);
        dprintf(writer[WRITE], "%cp", '\0');

        int wstatus;
       
        while (waitpid(pid, &wstatus, WNOHANG)) {
            printf("loop\n");
            // echo child's output in parent
            char c;
            while (read(reader[READ], &c, 1) == 1) {
                write(STDOUT_FILENO, &c, 1);
            }
            // pass parent's stdin to child
            while (read(STDIN_FILENO, &c, 1) == 1) {
                write(writer[WRITE], &c, 1);
            }
        } 
        printf("loop done\n");
        if (WIFEXITED(wstatus)) {
            printf("child exited normally with code %d\n", WEXITSTATUS(wstatus));
        }
        // wait for child proc to finish
//        waitpid(pid, NULL, 0);

        close(writer[WRITE]);
        close(reader[READ]);
    } else {
        // failure
        close(writer[READ]); close(writer[WRITE]);
        close(reader[READ]); close(reader[WRITE]);
        return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
}