lazysphere/src/commands/cat.c

#include "../command.h"

#include <ctype.h>

static struct {
    bool number_lines;
    bool number_non_empty;
    bool change_non_print;
    bool change_tabs;
    bool end_lines_dollar;
} flags;

static bool printable(char c) {
    switch (c) {
        case '\n': return true;
        case '\r': return true;
        case '\b': return true;
        case '\t': return true;
        default: return isprint(c);
    }
}

static void help(void) {
    printf("Usage: cat [-nbvteA] [FILE]...\n\n");
    printf("Print FILEs to stdout\n\n");
    printf("\t-n	Number output lines\n");
    printf("\t-b	Number nonempty lines\n");
    printf("\t-v	Show nonprinting characters as ^x or M-x\n");
    printf("\t-t	...and tabs as ^I\n");
    printf("\t-e	...and end lines with $\n");
    printf("\t-A	Same as -vte\n");
}

static void cat_file(FILE* file) {
    char c;
    size_t read;
    
    size_t line = 1;
    bool empty = true;
    bool newline = true;
    
    while ((read = fread(&c, 1, 1, file)) != 0) {
        if (c == '\n') {
            if (empty && flags.number_lines) {
                printf("\t%ld ", line);
            }
            if (flags.end_lines_dollar) {
                printf("$");
            }
            line++;
            newline = true;
            empty = true;
            goto print;
        } else {
            empty = false;
        }

        if (!newline) {
            goto print;
        }

        if (!empty && (flags.number_non_empty || flags.number_lines)) {
            printf("\t%ld ", line);
            newline = false;
        }
    print:
        if (!flags.change_non_print || printable(c)) {
            if (flags.change_tabs && c == '\t') {
                fwrite("^I", 1, 2, stdout);
            } else {
                fwrite(&c, 1, 1, stdout);
            }
        } else {
            c |= '@';
            fwrite(&c, 1, 1, stdout);
        }
    }
}

static int short_arg(char c, char* next) {
    UNUSED(next);
    switch (c) {
        case 'n':
            flags.number_lines = true;
            break;
        case 'b':
            flags.number_non_empty = true;
            break;
        case 'v':
            flags.change_non_print = true;
            break;
        case 't':
            flags.change_non_print = true;
            flags.change_tabs = true;
            break;
        case 'e':
            flags.change_non_print = true;
            flags.end_lines_dollar = true;
            break;
        case 'A':
            flags.change_non_print = true;
            flags.change_tabs = true;
            flags.end_lines_dollar = true;
            break;
        default:
            return ARG_INVALID;
    }
    return ARG_UNUSED;
}

COMMAND(cat) {

    flags.number_lines = false;
    flags.number_non_empty = false;
    flags.change_non_print = false;
    flags.change_tabs = false;
    flags.end_lines_dollar = false;

    int start = parse_args(argc, argv, help, short_arg, NULL);

    int arg_len = argc - start;

    if (arg_len < 1) {
        cat_file(stdin);
        return EXIT_SUCCESS;
    }

    for (int i = start; i < argc; i++) {
        FILE* in = get_file(argv[i], "r");
        cat_file(in);
        if (in != stdin)
            fclose(in);
    }

    return EXIT_SUCCESS;
}