lazysphere/command/cat.c

/**
 *  file: cat.c
 *  author: Tyler Murphy
 */

#include "command.h"
#include "lslib.h"

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

/**
 * Flags that are to be used with cat
 */
static struct {
    bool number_lines;      /* if to number the lines */
    bool number_non_empty;  /* if to number empty lines */
    bool change_non_print;  /* if to change non printable characters to be printable */
    bool change_tabs;       /* if to change tabs to ^I */
    bool end_lines_dollar;  /* if to print a $ at the end of lines */
} flags;

/**
 * Help function for cat
 */
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");
}

/**
 * Give a file pointer, cat all its contents
 * @param file the file to cat
 */
static void cat_file(FILE* file) {
    char c; /* current character read */
    size_t read; /* amount read */
    
    /* default arguments */
    size_t line = 1; /* what line we are on, 1 indexed */
    bool empty = true; /* if the current line is empty (nothing printed) */
    bool newline = true; /* if we are on a new line */
    
    /* read file a character at a time */
    while ((read = fread(&c, 1, 1, file)) != 0) {
        /* if its a new line, update the new line pointer */
        if (c == '\n') {
            if (empty && flags.number_lines) { /* print line number if set to */
                printf("\t%ld ", line);
            }
            if (flags.end_lines_dollar) { /* pint $ if set to */
                printf("$");
            }
            line++;
            newline = true; /* tell that the new line number is set to be printed */
            empty = true; /* set line to empty */
            goto print;
        } else {
            empty = false;
        }
        
        /* skip next check if not newline */
        if (!newline) {
            goto print;
        }

        /* if on a new line and is a valid char, print line number */
        if (!empty && (flags.number_non_empty || flags.number_lines)) {
            printf("\t%ld ", line);
            newline = false;
        }
    print:
        /* print character */
        if (!flags.change_non_print || printable_char(c)) {
            if (flags.change_tabs && c == '\t') {
                fwrite("^I", 1, 2, stdout); /* print ^I instead of tab */
            } else {
                fwrite(&c, 1, 1, stdout); /* print character to stdout */
            }
        } else { /* if set to change non print, fix char code */
            c |= '@';
            fwrite(&c, 1, 1, stdout);
        }
    }
}

/** 
 * Takes in each argument that has a single - and parses it 
 * @param c the character after the -
 * @param next the next argument in argv that hasnt been parsed
 * @reutrn if the next arg was used or if the arg was invalid
 */
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;
}

/**
 * Output a files contents
 */
COMMAND(cat_main) {

    int start;
    int arg_len;
    int i;

    /* set flag defaults */
    flags.number_lines = false;
    flags.number_non_empty = false;
    flags.change_non_print = false;
    flags.change_tabs = false;
    flags.end_lines_dollar = false;

    /* parse user arguments */
    start = parse_args(argc, argv, help, short_arg, NULL);

    /* get the number of arguments to cat */
    arg_len = argc - start;

    /* if not read from stdin */
    if (arg_len < 1) {
        cat_file(stdin);
        return EXIT_SUCCESS;
    }

    /* foreach file, try to open it, and then cat it */
    for (i = start; i < argc; i++) {
        FILE* in = get_file(argv[i], "r"); /* open file as read */
        cat_file(in); /* print it out */
        if (in != stdin)
            fclose(in);
    }

    return EXIT_SUCCESS; /* success */
}