harder lab14 ex

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

typedef enum {
  ORIGIN = 'o', LOW = 'l', UP = 'u', CAP = 'c'
} ProgModesE;

FILE *openFile(char path[], char mode[]) {
  FILE *f = NULL;
  if ((f = fopen(path, mode)) == NULL) {
    perror("");
    exit(-1);
  }
  return f;
}

void closeFile(FILE *f) {
  if (fclose(f) == EOF) {
    perror("");
  }
}

void readNWrite(ProgModesE mode, FILE *fin) {
  for (int ch, last = 0; (ch = fgetc(fin)) && !feof(fin); last = ch) {
    switch (mode) {
    case ORIGIN: break;
    case LOW:
      ch = tolower(ch);
      break;
    case UP:
      ch = toupper(ch);
      break;
    case CAP:
      if (!isalnum(last) && isalpha(ch)) {
        ch = toupper(ch);
      } else {
        ch = tolower(ch);
      }
      break;
    default:
      fprintf(stderr, "error!\n");
    }
    putchar(ch);
  }
}

int main(int argc, char **argv) {
  FILE *fin = NULL;
  ProgModesE mode = ORIGIN;
  for (int i = 1; i < argc; i++) {
    if (*argv[i] == '-') {
      mode = (ProgModesE)argv[i][1];
    } else {
      fin = openFile(argv[i], "r");
      readNWrite(mode, fin);
    }
  }
  if (fin != NULL) {
    closeFile(fin);
  }
  return 0;
}