summaryrefslogtreecommitdiffhomepage
path: root/coreutils/shuf.c
blob: b1a9d1254345ada2aa6957bd384acba3f4680762 (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
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
/* vi: set sw=4 ts=4: */
/*
 * shuf: Write a random permutation of the input lines to standard output.
 *
 * Copyright (C) 2014 by Bartosz Golaszewski <bartekgola@gmail.com>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

//config:config SHUF
//config:	bool "shuf (5.4 kb)"
//config:	default y
//config:	help
//config:	  Generate random permutations

//kbuild:lib-$(CONFIG_SHUF) += shuf.o
//applet:IF_SHUF(APPLET_NOEXEC(shuf, shuf, BB_DIR_USR_BIN, BB_SUID_DROP, shuf))

//usage:#define shuf_trivial_usage
//usage:       "[-e|-i L-H] [-n NUM] [-o FILE] [-z] [FILE|ARG...]"
//usage:#define shuf_full_usage "\n\n"
//usage:       "Randomly permute lines\n"
//usage:     "\n	-e	Treat ARGs as lines"
//usage:     "\n	-i L-H	Treat numbers L-H as lines"
//usage:     "\n	-n NUM	Output at most NUM lines"
//usage:     "\n	-o FILE	Write to FILE, not standard output"
//usage:     "\n	-z	End lines with zero byte, not newline"

#include "libbb.h"

/* This is a NOEXEC applet. Be very careful! */

#define OPT_e		(1 << 0)
#define OPT_i		(1 << 1)
#define OPT_n		(1 << 2)
#define OPT_o		(1 << 3)
#define OPT_z		(1 << 4)
#define OPT_STR		"ei:n:o:z"

/*
 * Use the Fisher-Yates shuffle algorithm on an array of lines.
 */
static void shuffle_lines(char **lines, unsigned numlines)
{
	unsigned i;
	unsigned r;
	char *tmp;

	srand(monotonic_us());

	for (i = numlines-1; i > 0; i--) {
		r = rand();
		/* RAND_MAX can be as small as 32767 */
		if (i > RAND_MAX)
			r ^= rand() << 15;
		r %= i + 1;
		tmp = lines[i];
		lines[i] = lines[r];
		lines[r] = tmp;
	}
}

int shuf_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int shuf_main(int argc, char **argv)
{
	unsigned opts;
	char *opt_i_str, *opt_n_str, *opt_o_str;
	unsigned i;
	char **lines;
	unsigned numlines;
	char eol;

	opt_complementary = "e--i:i--e"; /* mutually exclusive */
	opts = getopt32(argv, OPT_STR, &opt_i_str, &opt_n_str, &opt_o_str);

	argc -= optind;
	argv += optind;

	/* Prepare lines for shuffling - either: */
	if (opts & OPT_e) {
		/* make lines from command-line arguments */
		numlines = argc;
		lines = argv;
	} else
	if (opts & OPT_i) {
		/* create a range of numbers */
		char *dash;
		unsigned lo, hi;

		dash = strchr(opt_i_str, '-');
		if (!dash) {
			bb_error_msg_and_die("bad range '%s'", opt_i_str);
		}
		*dash = '\0';
		lo = xatou(opt_i_str);
		hi = xatou(dash + 1);
		*dash = '-';
		if (hi < lo) {
			bb_error_msg_and_die("bad range '%s'", opt_i_str);
		}

		numlines = (hi+1) - lo;
		lines = xmalloc(numlines * sizeof(lines[0]));
		for (i = 0; i < numlines; i++) {
			lines[i] = (char*)(uintptr_t)lo;
			lo++;
		}
	} else {
		/* default - read lines from stdin or the input file */
		FILE *fp;

		if (argc > 1)
			bb_show_usage();

		fp = xfopen_stdin(argv[0] ? argv[0] : "-");
		lines = NULL;
		numlines = 0;
		for (;;) {
			char *line = xmalloc_fgetline(fp);
			if (!line)
				break;
			lines = xrealloc_vector(lines, 6, numlines);
			lines[numlines++] = line;
		}
		fclose_if_not_stdin(fp);
	}

	if (numlines != 0)
		shuffle_lines(lines, numlines);

	if (opts & OPT_o)
		xmove_fd(xopen(opt_o_str, O_WRONLY|O_CREAT|O_TRUNC), STDOUT_FILENO);

	if (opts & OPT_n) {
		unsigned maxlines;
		maxlines = xatou(opt_n_str);
		if (numlines > maxlines)
			numlines = maxlines;
	}

	eol = '\n';
	if (opts & OPT_z)
		eol = '\0';

	for (i = 0; i < numlines; i++) {
		if (opts & OPT_i)
			printf("%u%c", (unsigned)(uintptr_t)lines[i], eol);
		else
			printf("%s%c", lines[i], eol);
	}

	fflush_stdout_and_exit(EXIT_SUCCESS);
}