summaryrefslogtreecommitdiff
path: root/inotail.c
blob: 5e98ebd3dc0c5898f1e82fe97b5ef8a23e7acfd1 (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
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
/*
 * inotail.c
 * A fast implementation of tail which uses the inotify API present in
 * recent versions of the Linux kernel.
 *
 * Copyright (C) 2005-2006, Tobias Klauser <tklauser@distanz.ch>
 *
 * The idea was taken from turbotail.
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation; either version 2, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

#define _GNU_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <getopt.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "inotify.h"
#include "inotify-syscalls.h"

#include "inotail.h"

#define PROGRAM_NAME "inotail"
#define BUFFER_SIZE 4096

/* Print header with filename before tailing the file? */
static char verbose = 0;

/* Tailing relative to begin or end of file */
static char from_begin = 0;

/* Command line options */
static const struct option long_opts[] = {
	{"bytes", required_argument, NULL, 'c'},
	{"follow", optional_argument, NULL, 'f'},
	{"lines", required_argument, NULL, 'n'},
	{"verbose", no_argument, NULL, 'v'},
	{"help", no_argument, NULL, 'h'},
	{"version", no_argument, NULL, 'V'},
	{NULL, 0, NULL, 0}
};

static void usage(const int status)
{
	fprintf(stderr, "Usage: %s [OPTION]... [FILE]...\n\n"
			"  -c N, --bytes=N    output the last N bytes\n"
			"  -f,   --follow     output as the file grows\n"
			"  -n N, --lines=N    output the last N lines (default: %d)\n"
			"  -v,   --verbose    print headers with file names\n"
			"  -h,   --help       show this help and exit\n"
			"  -V,   --version    show version and exit\n\n"
			"If the first character of N (the number of bytes or lines) is a `+',\n"
			"begin printing with the Nth item from the start of each file, otherwise,\n"
			"print the last N items in the file.\n", PROGRAM_NAME, DEFAULT_N_LINES);

	exit(status);
}

static void setup_file(struct file_struct *f)
{
	f->fd = -1;
	f->st_size = 0;
	f->ignore = 0;
	f->i_watch = -1;
}

static inline char *pretty_name(char *filename)
{
	return (strncmp(filename, "-", 1) == 0) ? "standard input" : filename;
}

static void write_header(char *filename)
{
	static unsigned short first_file = 1;

	fprintf(stdout, "%s==> %s <==\n", (first_file ? "" : "\n"), pretty_name(filename));
	first_file = 0;
}

static off_t lines_to_offset_from_end(struct file_struct *f, unsigned int n_lines)
{
	char buf[BUFFER_SIZE];
	off_t offset = f->st_size;

	n_lines++;	/* We also count the last \n */
	memset(&buf, 0, sizeof(buf));

	while (offset > 0 && n_lines > 0) {
		int i, rc;
		int block_size = BUFFER_SIZE;	/* Size of the current block we're reading */

		if (offset < BUFFER_SIZE)
			block_size = offset;

		/* Start of current block */
		offset -= block_size;

		lseek(f->fd, offset, SEEK_SET);

		rc = read(f->fd, &buf, block_size);
		if (rc < 0) {
			fprintf(stderr, "Error: Could not read from file '%s' (%s)\n", f->name, strerror(errno));
			return -1;
		}

		for (i = block_size; i > 0; i--) {
			if (buf[i] == '\n') {
				if (--n_lines == 0)
					return offset += i + 1; /* We don't want the first \n */
			}
		}
	}

	return offset;

}

static off_t lines_to_offset_from_begin(struct file_struct *f, unsigned int n_lines)
{
	char buf[BUFFER_SIZE];
	off_t offset = 0;

	/* tail everything for 'inotail -n +0' */
	if (n_lines == 0)
		return 0;

	n_lines--;
	memset(&buf, 0, sizeof(buf));

	while (offset <= f->st_size && n_lines > 0) {
		int i, rc;
		int block_size = BUFFER_SIZE;

		lseek(f->fd, offset, SEEK_SET);

		rc = read(f->fd, &buf, block_size);
		if (rc < 0) {
			fprintf(stderr, "Error: Could not read from file '%s' (%s)\n", f->name, strerror(errno));
			return -1;
		}

		for (i = 0; i < block_size; i++) {
			if (buf[i] == '\n') {
				if (--n_lines == 0)
					return offset + i + 1;
			}
		}

		offset += block_size;
	}

	return offset;
}

static off_t lines_to_offset(struct file_struct *f, unsigned int n_lines)
{
	if (from_begin)
		return lines_to_offset_from_begin(f, n_lines);
	else
		return lines_to_offset_from_end(f, n_lines);
}

static inline off_t bytes_to_offset(struct file_struct *f, unsigned int n_bytes)
{
	/* tail everything for 'inotail -c +0' */
	if (from_begin && n_bytes == 0)
		return 0;
	else
		return (from_begin ? ((off_t) n_bytes - 1) : (f->st_size - (off_t) n_bytes));
}

static int tail_pipe(struct file_struct *f)
{
	int rc;
	char buf[BUFFER_SIZE];

	if (verbose)
		write_header(f->name);

	/* We will just tail everything here */
	while ((rc = read(f->fd, &buf, BUFFER_SIZE)) > 0)
		write(STDOUT_FILENO, buf, (size_t) rc);

	return rc;
}

static int tail_file(struct file_struct *f, unsigned int n_units, char mode, char forever)
{
	int ret = -1;
	ssize_t bytes_read = 0;
	off_t offset = 0;
	char buf[BUFFER_SIZE];
	struct stat finfo;

	if (strncmp(f->name, "-", 1) == 0)
		f->fd = STDIN_FILENO;
	else {
		f->fd = open(f->name, O_RDONLY);
		if (f->fd < 0) {
			fprintf(stderr, "Error: Could not open file '%s' (%s)\n", f->name, strerror(errno));
			return ret;
		}
	}

	if (fstat(f->fd, &finfo) < 0) {
		fprintf(stderr, "Error: Could not stat file '%s' (%s)\n", f->name, strerror(errno));
		goto err;
	}

	if (!IS_TAILABLE(finfo.st_mode)) {
		fprintf(stderr, "Error: '%s' of unsupported file type\n", f->name);
		goto err;
	}

	/* We cannot seek on these */
	if (IS_PIPELIKE(finfo.st_mode) || f->fd == STDIN_FILENO)
		return tail_pipe(f);

	f->st_size = finfo.st_size;

	if (mode == M_LINES)
		offset = lines_to_offset(f, n_units);
	else
		offset = bytes_to_offset(f, n_units);

	/* We only get negative offsets on errors */
	if (offset < 0)
		goto err;

	if (verbose)
		write_header(f->name);

	lseek(f->fd, offset, SEEK_SET);

	while ((bytes_read = read(f->fd, &buf, BUFFER_SIZE)) > 0)
		write(STDOUT_FILENO, buf, (size_t) bytes_read);

	ret = 0;

	/* Let the fd open, we'll need it */
	if (forever)
		return ret;

err:
	if (close(f->fd) < 0) {
		fprintf(stderr, "Error: Could not close file '%s' (%s)\n", f->name, strerror(errno));
		ret = -1;
	}

	return ret;
}

static int handle_inotify_event(struct inotify_event *inev, struct file_struct *fil, int n_ignored)
{
	if (inev->mask & IN_MODIFY) {
		int rc;
		off_t offset;
		char fbuf[BUFFER_SIZE];
		struct stat finfo;

#if 0
		fil->fd = open(fil->name, O_RDONLY);
		if (fil->fd < 0) {
			fprintf(stderr, "Error: Could not open file '%s' (%s)\n", fil->name, strerror(errno));
			goto ignore;
		}
#endif
		if (fstat(fil->fd, &finfo) < 0) {
			fprintf(stderr, "Error: Could not stat file '%s' (%s)\n", fil->name, strerror(errno));
			goto ignore;
		}

		offset = fil->st_size;
		fil->st_size = finfo.st_size;
		memset(&fbuf, 0, sizeof(fbuf));

		if (verbose)
			write_header(fil->name);

		lseek(fil->fd, offset, SEEK_SET);
		while ((rc = read(fil->fd, &fbuf, BUFFER_SIZE)) != 0)
			write(STDOUT_FILENO, fbuf, rc);
#if 0
		close(fil->fd);
#endif
		return n_ignored;
	} else if (inev->mask & IN_DELETE_SELF) {
		fprintf(stderr, "File '%s' deleted.\n", fil->name);
	} else if (inev->mask & IN_MOVE_SELF) {
		fprintf(stderr, "File '%s' moved.\n", fil->name);
		return n_ignored;
	} else if (inev->mask & IN_UNMOUNT) {
		fprintf(stderr, "Device containing file '%s' unmounted.\n", fil->name);
	}

ignore:
	if (close(fil->fd) < 0)
		fprintf(stderr, "Error: Could not close file '%s' (%s)\n", fil->name, strerror(errno));

	fil->ignore = 1;
	n_ignored++;

	return n_ignored;
}

static int watch_files(struct file_struct *f, int n_files)
{
	int ifd, i, n_ignored = 0;
	unsigned buflen = 2 * n_files * sizeof(struct inotify_event);
	struct inotify_event *inev;
	char *buf;

	ifd = inotify_init();
	if (ifd < 0) {
		fprintf(stderr, "Error: Inotify is not supported by the kernel you're currently running.\n");
		exit(EXIT_FAILURE);
	}

	for (i = 0; i < n_files; i++) {
		if (!f[i].ignore)
			f[i].i_watch = inotify_add_watch(ifd, f[i].name,
						IN_MODIFY|IN_DELETE_SELF|IN_MOVE_SELF|IN_UNMOUNT);
		else
			n_ignored++;
	}

	buf = malloc(buflen);
	memset(buf, 0, buflen);

	while (n_ignored < n_files) {
		int len;

		len = read(ifd, buf, buflen);
		inev = (struct inotify_event *) buf;

		while (len > 0) {
			struct file_struct *fil = NULL;

			/* Which file has produced the event? */
			for (i = 0; i < n_files; i++) {
				if (!f[i].ignore && f[i].fd >= 0 && f[i].i_watch == inev->wd) {
					fil = &f[i];
					break;
				}
			}

			if (unlikely(!fil))
				break;

			n_ignored = handle_inotify_event(inev, fil, n_ignored);
			len -= sizeof(struct inotify_event) + inev->len;
			inev = (struct inotify_event *) ((char *) inev + sizeof(struct inotify_event) + inev->len);
		}
	}

	free(buf);
	close(ifd);

	return n_ignored;
}

int main(int argc, char **argv)
{
	int i, c, ret = 0;
	int n_files = 0;
	int n_units = DEFAULT_N_LINES;
	char forever = 0, mode = M_LINES;
	char **filenames;
	struct file_struct *files;

	while ((c = getopt_long(argc, argv, "c:n:fvVh", long_opts, NULL)) != -1) {
		switch (c) {
		case 'c':
			mode = M_BYTES;
			/* fall through */
		case 'n':
			if (*optarg == '+')
				from_begin = 1;
			else if (*optarg == '-')
				optarg++;
			n_units = strtoul(optarg, NULL, 0);
			if (n_units < 0)
				n_units = 0;
			break;
                case 'f':
			forever = 1;
			break;
		case 'v':
			verbose = 1;
			break;
		case 'V':
			fprintf(stderr, "%s %s\n", PROGRAM_NAME, VERSION);
			return 0;
		case 'h':
			usage(EXIT_SUCCESS);
		default:
			usage(EXIT_FAILURE);
		}
	}

	/* Do we have some files to read from? */
	if (optind < argc) {
		n_files = argc - optind;
		filenames = argv + optind;
	} else {
		/* It must be stdin then */
		static char *dummy_stdin = "-";
		n_files++;
		filenames = &dummy_stdin;

		/* POSIX says that -f is ignored if no file operand is
		   specified and standard input is a pipe. */
		if (forever) {
			struct stat finfo;
			if (fstat(STDIN_FILENO, &finfo) == 0
					&& IS_PIPELIKE(finfo.st_mode))
				forever = 0;
		}
	}

	files = malloc(n_files * sizeof(struct file_struct));
	if (unlikely(!files)) {
		fprintf(stderr, "Error: Not enough memory (%s)\n", strerror(errno));
		exit(EXIT_FAILURE);
	}

	for (i = 0; i < n_files; i++) {
		files[i].name = filenames[i];
		setup_file(&files[i]);
		ret = tail_file(&files[i], n_units, mode, forever);
		if (ret < 0)
			files[i].ignore = 1;
	}

	if (forever)
		ret = watch_files(files, n_files);

	free(files);

	return ret;
}