咱这是多久没写 C 了……

wc.c

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

#define BUFFER_SIZE (1024)

int main (int argc, char **argv) {

  int flags = 0;
  char* path = NULL;

  argv++; argc--; // Skip $0

  while (argc) {
    fprintf(stderr, "DEBUG argv %s\n", *argv);
    if (!strcmp(*argv, "-c")) {
      flags |= 0x04;
    } else if (!strcmp(*argv, "-w")) {
      flags |= 0x02;
    } else if (!strcmp(*argv, "-l")) {
      flags |= 0x01;
    } else {
      path = *argv;
    }

    argv++; argc--;
  }

  if (flags == 0) flags = 0x07;

  FILE *fp = freopen(path, "r", stdin);

  char buffer[BUFFER_SIZE];
  size_t buflen = 0;

  int line_count = 0;
  int word_count = 0;
  int char_count = 0;
  char last_char = ' ';

  do {
    buflen = fread(buffer, sizeof(char), BUFFER_SIZE, fp);
    for (int i = 0; i != buflen; i++) {
      char it = buffer[i];
      if (it == '\n') { line_count++; it = ' '; }
      if (it != last_char && it == ' ') word_count++;
      last_char = it;
    }
    char_count += buflen;
  } while (buflen == BUFFER_SIZE);

  if (last_char != ' ') word_count++;

  if (flags & 0x01) fprintf(stdout, "%d\t", line_count);
  if (flags & 0x02) fprintf(stdout, "%d\t", word_count);
  if (flags & 0x04) fprintf(stdout, "%d\t", char_count);
  fprintf(stdout, "%s\n", path);

  return 0;

}

用时1h……