c-inter-imp/chap1/double.c

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

int linenum;

int getword(FILE *, char *, int);
void doubleword(char *, FILE *);

int main(int argc, char *argv[]) {
    int i;

    for (i = 1; i < argc; i++) {
        FILE *fp = fopen(argv[i], "r");
        if (fp == NULL) {
            fprintf(
                stderr,
                "%s: can't open '%s' (%s)\n",
                argv[0], argv[i], strerror(errno)
            );
        } else {
            doubleword(argv[i], fp);
            fclose(fp);
        }
    }
    if (argc == 1) doubleword(NULL, stdin);
    return EXIT_SUCCESS;
}

// getword reads a word from fp into buf, returning true if it was able to do so.
int getword(FILE *fp, char *buf, int size) {
    int c;
    c = getc(fp);

    // Scan forward to nonspace or EOF.
    for ( ; c != EOF && isspace(c); c = getc(fp))
        if (c == '\n')
            linenum++;

    // Copy word to buff.
    {
        int i = 0;
        for ( ; c != EOF && !isspace(c); c = getc(fp))
            if (i < size - 1)
                buf[i++] = tolower(c);
        if (i < size)
            buf[i] = '\0';
    }

    if (c != EOF)
        ungetc(c, fp);
    return  buf[0] != '\0';
}

void doubleword(char *name, FILE *fp) {
  char prev[128], word[128];

  linenum = 1;
  prev[0] = '\0';
  while (getword(fp, word, sizeof word)) {
    if (isalpha(word[0]) && strcmp(prev, word) == 0)
      // word is a duplicate
      {
        if (name)
          printf("%s:", name);
        printf("%d: %s\n", linenum, word);
      }
    strcpy(prev, word);
  }
}