aboutsummaryrefslogtreecommitdiff
path: root/coreutils/cmp.c
blob: ae3f5027927dd8ffcb15db04fa55a2a1363bcf82 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
/* 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 tarball for details.
 */

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

/* Mar 16, 2003      Manuel Novoa III   (mjn3@codepoet.org)
 *
 * Original version majorly reworked for SUSv3 compliance, bug fixes, and
 * size optimizations.  Changes include:
 * 1) Now correctly distinguishes between errors and actual file differences.
 * 2) Proper handling of '-' args.
 * 3) Actual error checking of i/o.
 * 4) Accept SUSv3 -l option.  Note that we use the slightly nicer gnu format
 *    in the '-l' case.
 */

#include "busybox.h"

static FILE *cmp_xfopen_input(const char * const filename)
{
	FILE *fp;

	if ((fp = bb_wfopen_input(filename)) != NULL) {
		return fp;
	}

	exit(bb_default_error_retval);	/* We already output an error message. */
}

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

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

int cmp_main(int argc, char **argv)
{
	FILE *fp1, *fp2, *outfile = stdout;
	const char *filename1, *filename2 = "-";
	const char *fmt;
	int c1, c2, char_pos = 0, line_pos = 1;
	unsigned opt;
	int retval = 0;

	bb_default_error_retval = 2;	/* 1 is returned if files are different. */

	opt = bb_getopt_ulflags(argc, argv, opt_chars);

	if ((opt & (CMP_OPT_s|CMP_OPT_l))
			|| (((unsigned int)(--argc - optind)) > 1))
		bb_show_usage();

	fp1 = cmp_xfopen_input(filename1 = *(argv += optind));

	if (*++argv) {
		filename2 = *argv;
	}
	fp2 = cmp_xfopen_input(filename2);

	if (fp1 == fp2) {			/* Paranioa 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;
	}

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

	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) {
				xferror(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. */
				xfflush_stdout();
			}
			if (!opt & CMP_OPT_s) {
				if (opt & CMP_OPT_l) {
					line_pos = c1;	/* line_pos is unused in the -l case. */
				}
				bb_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);

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

	bb_fflush_stdout_and_exit(retval);
}