#include <stdlib.h>
#include <stdio.h>
#include <spawn.h>
#include <sys/wait.h>
#include <string.h>

extern char** environ;

// ./run_grep at f1.txt f2.txt f3.txt
int main(int argc, char *argv[]) {
    if (argc <= 2 ) {
        fprintf(stderr, "Usage: %s <pattern> <filename>...\n", argv[0]);
        return 1;
    }
    
    int n_processes = argc - 2;

    pid_t pid[n_processes];
    for (int i = 0; i < n_processes; i++) {
        char *args[] = {"/bin/grep", "-H", argv[1], argv[i + 2], NULL};
        int ret = posix_spawn(&pid[i], args[0], NULL, NULL, args, environ); 
        if (ret != 0) {
            fprintf(stderr, "%s\n", strerror(ret));
            return 1;
        }
    }
    // grep 0 matches
    //      1 did not
    //      2 error
    int status;
    int n_files_matched = 0;
    for (int i = 0; i < n_processes; i++) {  
        waitpid(pid[i], &status, 0);
        //printf("stat %d\n", WEXITSTATUS(status));
        if (WEXITSTATUS(status) == 0){
            n_files_matched++;
        }
    }
    printf("%d files matched\n", n_files_matched);
    return 0;
}