wc.c

#include <stdio.h>


int is_blank(int c) {
    return c == ' ' || c == '\t' || c == '\n';
}

int is_opt(char *o, char opt) {
    return o[0] == '-' && o[1] == opt && o[2] == '\0';
}

int main(int argc, char *argv[]) {
    int total_chars = 0;
    int total_lines = 0;
    int total_words = 0;
    // start with blank to avoid corner case of leading blanks
    char prev_char = ' ';
    char c;

    int count_chars = 0;
    int count_lines = 0;
    int count_words = 0;
    int in_word = 0;

    int has_options = 0;

    FILE *fp = stdin;
    char *filename;

    
    for (int i = 1 ; i < argc ; i++) {
        if (!has_options && argv[i][0] != '-') {
            fp = fopen(argv[i], "r");
            filename = argv[i];
            break;
        }
        if (is_opt(argv[i], 'c')) {
            has_options = 1;
            count_chars = 1;
        } else if (is_opt(argv[i], 'l')) {
            has_options = 1;
            count_lines = 1;
        } else if (is_opt(argv[i], 'w')) {
            has_options = 1;
            count_words = 1;
        } else {
            printf("invalid argument \"%s\"\n", argv[i]);
            return 1;
        }
    }
    if (!has_options) {
        count_chars = count_lines = count_words = 1;
    }

    while ((c = fgetc(fp)) != EOF) {
        total_chars++;
        if (c == '\n') {
            total_lines++;
        }
        if (is_blank(c) && !is_blank(prev_char)) {
            total_words++;
        }
        prev_char = c;
    }
    // count last word (or first and only word)
    if (total_chars > 0 && !is_blank(prev_char)) {
        total_words++;
    }

    if (count_lines) {
        printf("\t%d", total_lines);
    }
    if (count_words) {
        printf("\t%d", total_words);
    }
    if (count_chars) {
        printf("\t%d", total_chars);
    }
    if (fp != stdin) {
        printf(" %s", filename);
    }
    printf("\n");

    if (fp && fp != stdin) {
        fclose(fp);
    }

    return 0;
}