source: MondoRescue/branches/3.3/mindi-busybox/editors/cmp.c@ 3723

/* vi: set sw=4 ts=4: */
/*
 * Mini cmp implementation for busybox
 *
 * Copyright (C) 2000,2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

/* BB_AUDIT SUSv3 (virtually) compliant -- uses nicer GNU format for -l. */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/cmp.html */

//config:config CMP
//config:   bool "cmp"
//config:   default y
//config:   help
//config:     cmp is used to compare two files and returns the result
//config:     to standard output.

//kbuild:lib-$(CONFIG_CMP) += cmp.o

//applet:IF_CMP(APPLET(cmp, BB_DIR_USR_BIN, BB_SUID_DROP))

//usage:#define cmp_trivial_usage
//usage:       "[-l] [-s] FILE1 [FILE2" IF_DESKTOP(" [SKIP1 [SKIP2]]") "]"
//usage:#define cmp_full_usage "\n\n"
//usage:       "Compare FILE1 with FILE2 (or stdin)\n"
//usage:     "\n    -l  Write the byte numbers (decimal) and values (octal)"
//usage:     "\n        for all differing bytes"
//usage:     "\n    -s  Quiet"

#include "libbb.h"

static const char fmt_eof[] ALIGN1 = "cmp: EOF on %s\n";
static const char fmt_differ[] ALIGN1 = "%s %s differ: char %"OFF_FMT"u, line %u\n";
// This fmt_l_opt uses gnu-isms.  SUSv3 would be "%.0s%.0s%"OFF_FMT"u %o %o\n"
static const char fmt_l_opt[] ALIGN1 = "%.0s%.0s%"OFF_FMT"u %3o %3o\n";

static const char opt_chars[] ALIGN1 = "sl";
#define CMP_OPT_s (1<<0)
#define CMP_OPT_l (1<<1)

int cmp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int cmp_main(int argc UNUSED_PARAM, char **argv)
{
    FILE *fp1, *fp2, *outfile = stdout;
    const char *filename1, *filename2 = "-";
    off_t skip1 = 0, skip2 = 0, char_pos = 0;
    int line_pos = 1; /* Hopefully won't overflow... */
    const char *fmt;
    int c1, c2;
    unsigned opt;
    int retval = 0;

    opt_complementary = "-1"
            IF_DESKTOP(":?4")
            IF_NOT_DESKTOP(":?2")
            ":l--s:s--l";
    opt = getopt32(argv, opt_chars);
    argv += optind;

    filename1 = *argv;
    if (*++argv) {
        filename2 = *argv;
        if (ENABLE_DESKTOP && *++argv) {
            skip1 = XATOOFF(*argv);
            if (*++argv) {
                skip2 = XATOOFF(*argv);
            }
        }
    }

    xfunc_error_retval = 2;  /* missing file results in exitcode 2 */
    if (opt & CMP_OPT_s)
        logmode = 0;  /* -s suppresses open error messages */
    fp1 = xfopen_stdin(filename1);
    fp2 = xfopen_stdin(filename2);
    if (fp1 == fp2) {       /* Paranoia check... stdin == stdin? */
        /* Note that we don't bother reading stdin.  Neither does gnu wc.
         * But perhaps we should, so that other apps down the chain don't
         * get the input.  Consider 'echo hello | (cmp - - && cat -)'.
         */
        return 0;
    }
    logmode = LOGMODE_STDIO;

    if (opt & CMP_OPT_l)
        fmt = fmt_l_opt;
    else
        fmt = fmt_differ;

    if (ENABLE_DESKTOP) {
        while (skip1) { getc(fp1); skip1--; }
        while (skip2) { getc(fp2); skip2--; }
    }
    do {
        c1 = getc(fp1);
        c2 = getc(fp2);
        ++char_pos;
        if (c1 != c2) {         /* Remember: a read error may have occurred. */
            retval = 1;     /* But assume the files are different for now. */
            if (c2 == EOF) {
                /* We know that fp1 isn't at EOF or in an error state.  But to
                 * save space below, things are setup to expect an EOF in fp1
                 * if an EOF occurred.  So, swap things around.
                 */
                fp1 = fp2;
                filename1 = filename2;
                c1 = c2;
            }
            if (c1 == EOF) {
                die_if_ferror(fp1, filename1);
                fmt = fmt_eof;  /* Well, no error, so it must really be EOF. */
                outfile = stderr;
                /* There may have been output to stdout (option -l), so
                 * make sure we fflush before writing to stderr. */
                fflush_all();
            }
            if (!(opt & CMP_OPT_s)) {
                if (opt & CMP_OPT_l) {
                    line_pos = c1;  /* line_pos is unused in the -l case. */
                }
                fprintf(outfile, fmt, filename1, filename2, char_pos, line_pos, c2);
                if (opt) {  /* This must be -l since not -s. */
                    /* If we encountered an EOF,
                     * the while check will catch it. */
                    continue;
                }
            }
            break;
        }
        if (c1 == '\n') {
            ++line_pos;
        }
    } while (c1 != EOF);

    die_if_ferror(fp1, filename1);
    die_if_ferror(fp2, filename2);

    fflush_stdout_and_exit(retval);
}