LXR busybox/editors/cmp.c

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Mini cmp implementation for busybox
   4 *
   5 * Copyright (C) 2000,2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
   6 *
   7 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8 */
   9//config:config CMP
  10//config:       bool "cmp (4.9 kb)"
  11//config:       default y
  12//config:       help
  13//config:       cmp is used to compare two files and returns the result
  14//config:       to standard output.
  15
  16//applet:IF_CMP(APPLET(cmp, BB_DIR_USR_BIN, BB_SUID_DROP))
  17
  18//kbuild:lib-$(CONFIG_CMP) += cmp.o
  19
  20//usage:#define cmp_trivial_usage
  21//usage:       "[-l] [-s] FILE1 [FILE2" IF_DESKTOP(" [SKIP1 [SKIP2]]") "]"
  22//usage:#define cmp_full_usage "\n\n"
  23//usage:       "Compare FILE1 with FILE2 (or stdin)\n"
  24//usage:     "\n        -l      Write the byte numbers (decimal) and values (octal)"
  25//usage:     "\n                for all differing bytes"
  26//usage:     "\n        -s      Quiet"
  27
  28/* BB_AUDIT SUSv3 (virtually) compliant -- uses nicer GNU format for -l. */
  29/* http://www.opengroup.org/onlinepubs/007904975/utilities/cmp.html */
  30
  31#include "libbb.h"
  32
  33static const char fmt_eof[] ALIGN1 = "cmp: EOF on %s\n";
  34static const char fmt_differ[] ALIGN1 = "%s %s differ: char %"OFF_FMT"u, line %u\n";
  35// This fmt_l_opt uses gnu-isms.  SUSv3 would be "%.0s%.0s%"OFF_FMT"u %o %o\n"
  36static const char fmt_l_opt[] ALIGN1 = "%.0s%.0s%"OFF_FMT"u %3o %3o\n";
  37
  38#define OPT_STR "sl"
  39#define CMP_OPT_s (1<<0)
  40#define CMP_OPT_l (1<<1)
  41
  42int cmp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  43int cmp_main(int argc UNUSED_PARAM, char **argv)
  44{
  45        FILE *fp1, *fp2, *outfile = stdout;
  46        const char *filename1, *filename2 = "-";
  47        off_t skip1 = 0, skip2 = 0, char_pos = 0;
  48        int line_pos = 1; /* Hopefully won't overflow... */
  49        const char *fmt;
  50        int c1, c2;
  51        unsigned opt;
  52        int retval = 0;
  53
  54        opt = getopt32(argv, "^"
  55                        OPT_STR
  56                        "\0" "-1"
  57                        IF_DESKTOP(":?4")
  58                        IF_NOT_DESKTOP(":?2")
  59                        ":l--s:s--l"
  60        );
  61        argv += optind;
  62
  63        filename1 = *argv;
  64        if (*++argv) {
  65                filename2 = *argv;
  66                if (ENABLE_DESKTOP && *++argv) {
  67                        skip1 = XATOOFF(*argv);
  68                        if (*++argv) {
  69                                skip2 = XATOOFF(*argv);
  70                        }
  71                }
  72        }
  73
  74        xfunc_error_retval = 2;  /* missing file results in exitcode 2 */
  75        if (opt & CMP_OPT_s)
  76                logmode = 0;  /* -s suppresses open error messages */
  77        fp1 = xfopen_stdin(filename1);
  78        fp2 = xfopen_stdin(filename2);
  79        if (fp1 == fp2) {               /* Paranoia check... stdin == stdin? */
  80                /* Note that we don't bother reading stdin.  Neither does gnu wc.
  81                 * But perhaps we should, so that other apps down the chain don't
  82                 * get the input.  Consider 'echo hello | (cmp - - && cat -)'.
  83                 */
  84                return 0;
  85        }
  86        logmode = LOGMODE_STDIO;
  87
  88        if (opt & CMP_OPT_l)
  89                fmt = fmt_l_opt;
  90        else
  91                fmt = fmt_differ;
  92
  93        if (ENABLE_DESKTOP) {
  94                while (skip1) { getc(fp1); skip1--; }
  95                while (skip2) { getc(fp2); skip2--; }
  96        }
  97        do {
  98                c1 = getc(fp1);
  99                c2 = getc(fp2);
 100                ++char_pos;
 101                if (c1 != c2) {                 /* Remember: a read error may have occurred. */
 102                        retval = 1;             /* But assume the files are different for now. */
 103                        if (c2 == EOF) {
 104                                /* We know that fp1 isn't at EOF or in an error state.  But to
 105                                 * save space below, things are setup to expect an EOF in fp1
 106                                 * if an EOF occurred.  So, swap things around.
 107                                 */
 108                                fp1 = fp2;
 109                                filename1 = filename2;
 110                                c1 = c2;
 111                        }
 112                        if (c1 == EOF) {
 113                                die_if_ferror(fp1, filename1);
 114                                fmt = fmt_eof;  /* Well, no error, so it must really be EOF. */
 115                                outfile = stderr;
 116                                /* There may have been output to stdout (option -l), so
 117                                 * make sure we fflush before writing to stderr. */
 118                                fflush_all();
 119                        }
 120                        if (!(opt & CMP_OPT_s)) {
 121                                if (opt & CMP_OPT_l) {
 122                                        line_pos = c1;  /* line_pos is unused in the -l case. */
 123                                }
 124                                fprintf(outfile, fmt, filename1, filename2, char_pos, line_pos, c2);
 125                                if (opt) {      /* This must be -l since not -s. */
 126                                        /* If we encountered an EOF,
 127                                         * the while check will catch it. */
 128                                        continue;
 129                                }
 130                        }
 131                        break;
 132                }
 133                if (c1 == '\n') {
 134                        ++line_pos;
 135                }
 136        } while (c1 != EOF);
 137
 138        die_if_ferror(fp1, filename1);
 139        die_if_ferror(fp2, filename2);
 140
 141        fflush_stdout_and_exit(retval);
 142}
 143