tech06-1.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/wait.h>

enum ErrorCodes { SUCCES, BAD_INPUT, BAD_OPEN, BAD_EXEC, BAD_FORK };
enum { EXPR_LEN = 4096 };

const char* c_code_format = "#include<stdio.h>\n"
                            "int main(void) {\n"
                            "   printf(\"%%d\\n\", (%s));\n"
                            "   return 0;\n"
                            "}\n\0";

void remove_tmp_files(void)
{
    unlink("tmp.c");
    unlink("tmp.out");
}

int main(void)
{

    size_t len = EXPR_LEN;
    char expression[EXPR_LEN] = "";

    if (NULL == fgets(expression, len, stdin)) {
        return BAD_INPUT;
    }

    FILE* tmp_c_f = fopen("tmp.c", "w");
    if (NULL == tmp_c_f) {
        return BAD_OPEN;
    }

    fprintf(tmp_c_f, c_code_format, expression);

    fclose(tmp_c_f);

    pid_t compilation_pid = fork();

    if (-1 == compilation_pid) {
        remove_tmp_files();
        return BAD_FORK;
    }

    else if (0 == compilation_pid) {
        execlp("gcc", "gcc", "-std=c11", "tmp.c", "-o", "tmp.out", NULL);
    }

    else {
        int compilation_status = 0;
        waitpid(compilation_pid, &compilation_status, 0);
    }

    pid_t running_pid = fork();

    if (-1 == running_pid) {
        remove_tmp_files();
        return BAD_FORK;
    }

    else if (0 == running_pid) {
        execlp("./tmp.out", "tmp.out", NULL);
    }

    else {
        int running_status = 0;
        waitpid(running_pid, &running_status, 0);
        remove_tmp_files();
    }

    return 0;
}