1 /* vi: set sw=4 ts=4: */
4 /* This file contains _two_ implementations of tail. One is
5 * a bit more full featured, but costs 6k. The other (i.e. the
6 * SIMPLE_TAIL one) is less capable, but is good enough for about
7 * 99% of the things folks want to use tail for, and only costs 2k.
11 #ifdef BB_FEATURE_SIMPLE_TAIL
13 /* tail -- output the last part of file(s)
14 Copyright (C) 89, 90, 91, 95, 1996 Free Software Foundation, Inc.
16 This program is free software; you can redistribute it and/or modify
17 it under the terms of the GNU General Public License as published by
18 the Free Software Foundation; either version 2, or (at your option)
21 This program is distributed in the hope that it will be useful,
22 but WITHOUT ANY WARRANTY; without even the implied warranty of
23 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
24 GNU General Public License for more details.
26 You should have received a copy of the GNU General Public License
27 along with this program; if not, write to the Free Software
28 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
30 Original version by Paul Rubin <phr@ocf.berkeley.edu>.
31 Extensions by David MacKenzie <djm@gnu.ai.mit.edu>.
32 tail -f for multiple files by Ian Lance Taylor <ian@airs.com>.
34 Rewrote the option parser, removed locales support,
35 and generally busyboxed, Erik Andersen <andersen@lineo.com>
37 Removed superfluous options and associated code ("-c", "-n", "-q").
38 Removed "tail -f" support for multiple files.
39 Both changes by Friedrich Vedder <fwv@myrtle.lahn.de>.
46 #include <sys/types.h>
52 #define XWRITE(fd, buffer, n_bytes) \
54 if (n_bytes > 0 && fwrite ((buffer), 1, (n_bytes), stdout) == 0) \
55 errorMsg("write error"); \
58 /* Number of items to tail. */
59 #define DEFAULT_N_LINES 10
61 /* Size of atomic reads. */
63 #define BUFSIZ (512 * 8)
66 /* If nonzero, read from the end of one file until killed. */
69 /* If nonzero, print filename headers. */
70 static int print_headers;
72 const char tail_usage[] =
73 "tail [OPTION] [FILE]...\n\n"
74 "Print last 10 lines of each FILE to standard output.\n"
75 "With more than one FILE, precede each with a header giving the\n"
76 "file name. With no FILE, or when FILE is -, read standard input.\n\n"
78 "\t-n NUM\t\tPrint last NUM lines instead of first 10\n"
80 "\t-f\t\tOutput data as the file grows. This version\n"
81 "\t\t\tof 'tail -f' supports only one file at a time.\n";
84 static void write_header(const char *filename)
86 static int first_file = 1;
88 printf("%s==> %s <==\n", (first_file ? "" : "\n"), filename);
92 /* Print the last N_LINES lines from the end of file FD.
93 Go backward through the file, reading `BUFSIZ' bytes at a time (except
94 probably the first), until we hit the start of the file or have
96 POS starts out as the length of the file (the offset of the last
97 byte of the file + 1).
98 Return 0 if successful, 1 if an error occurred. */
101 file_lines(const char *filename, int fd, long int n_lines, off_t pos)
105 int i; /* Index into `buffer' for scanning. */
110 /* Set `bytes_read' to the size of the last, probably partial, buffer;
111 0 < `bytes_read' <= `BUFSIZ'. */
112 bytes_read = pos % BUFSIZ;
115 /* Make `pos' a multiple of `BUFSIZ' (0 if the file is short), so that all
116 reads will be on block boundaries, which might increase efficiency. */
118 lseek(fd, pos, SEEK_SET);
119 bytes_read = fullRead(fd, buffer, bytes_read);
120 if (bytes_read == -1)
121 errorMsg("read error");
123 /* Count the incomplete line on files that don't end with a newline. */
124 if (bytes_read && buffer[bytes_read - 1] != '\n')
128 /* Scan backward, counting the newlines in this bufferfull. */
129 for (i = bytes_read - 1; i >= 0; i--) {
130 /* Have we counted the requested number of newlines yet? */
131 if (buffer[i] == '\n' && n_lines-- == 0) {
132 /* If this newline wasn't the last character in the buffer,
133 print the text after it. */
134 if (i != bytes_read - 1)
135 XWRITE(STDOUT_FILENO, &buffer[i + 1],
136 bytes_read - (i + 1));
140 /* Not enough newlines in that bufferfull. */
142 /* Not enough lines in the file; print the entire file. */
143 lseek(fd, (off_t) 0, SEEK_SET);
147 lseek(fd, pos, SEEK_SET);
149 while ((bytes_read = fullRead(fd, buffer, BUFSIZ)) > 0);
150 if (bytes_read == -1)
151 errorMsg("read error");
156 /* Print the last N_LINES lines from the end of the standard input,
157 open for reading as pipe FD.
158 Buffer the text as a linked list of LBUFFERs, adding them as needed.
159 Return 0 if successful, 1 if an error occured. */
161 static int pipe_lines(const char *filename, int fd, long int n_lines)
166 struct linebuffer *next;
168 typedef struct linebuffer LBUFFER;
169 LBUFFER *first, *last, *tmp;
170 int i; /* Index into buffers. */
171 int total_lines = 0; /* Total number of newlines in all buffers. */
174 first = last = (LBUFFER *) xmalloc(sizeof(LBUFFER));
175 first->nbytes = first->nlines = 0;
177 tmp = (LBUFFER *) xmalloc(sizeof(LBUFFER));
179 /* Input is always read into a fresh buffer. */
180 while ((tmp->nbytes = fullRead(fd, tmp->buffer, BUFSIZ)) > 0) {
184 /* Count the number of newlines just read. */
185 for (i = 0; i < tmp->nbytes; i++)
186 if (tmp->buffer[i] == '\n')
188 total_lines += tmp->nlines;
190 /* If there is enough room in the last buffer read, just append the new
191 one to it. This is because when reading from a pipe, `nbytes' can
192 often be very small. */
193 if (tmp->nbytes + last->nbytes < BUFSIZ) {
194 memcpy(&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes);
195 last->nbytes += tmp->nbytes;
196 last->nlines += tmp->nlines;
198 /* If there's not enough room, link the new buffer onto the end of
199 the list, then either free up the oldest buffer for the next
200 read if that would leave enough lines, or else malloc a new one.
201 Some compaction mechanism is possible but probably not
203 last = last->next = tmp;
204 if (total_lines - first->nlines > n_lines) {
206 total_lines -= first->nlines;
209 tmp = (LBUFFER *) xmalloc(sizeof(LBUFFER));
212 if (tmp->nbytes == -1)
213 errorMsg("read error");
217 /* This prevents a core dump when the pipe contains no newlines. */
221 /* Count the incomplete line on files that don't end with a newline. */
222 if (last->buffer[last->nbytes - 1] != '\n') {
227 /* Run through the list, printing lines. First, skip over unneeded
229 for (tmp = first; total_lines - tmp->nlines > n_lines; tmp = tmp->next)
230 total_lines -= tmp->nlines;
232 /* Find the correct beginning, then print the rest of the file. */
233 if (total_lines > n_lines) {
236 /* Skip `total_lines' - `n_lines' newlines. We made sure that
237 `total_lines' - `n_lines' <= `tmp->nlines'. */
239 for (i = total_lines - n_lines; i; --i)
240 while (*cp++ != '\n')
242 i = cp - tmp->buffer;
245 XWRITE(STDOUT_FILENO, &tmp->buffer[i], tmp->nbytes - i);
247 for (tmp = tmp->next; tmp; tmp = tmp->next)
248 XWRITE(STDOUT_FILENO, tmp->buffer, tmp->nbytes);
253 free((char *) first);
259 /* Display file FILENAME from the current position in FD to the end.
260 If `forever' is nonzero, keep reading from the end of the file
261 until killed. Return the number of bytes read from the file. */
263 static long dump_remainder(const char *filename, int fd)
271 while ((bytes_read = fullRead(fd, buffer, BUFSIZ)) > 0) {
272 XWRITE(STDOUT_FILENO, buffer, bytes_read);
275 if (bytes_read == -1)
276 errorMsg("read error");
286 /* Output the last N_LINES lines of file FILENAME open for reading in FD.
287 Return 0 if successful, 1 if an error occurred. */
289 static int tail_lines(const char *filename, int fd, long int n_lines)
295 write_header(filename);
297 if (fstat(fd, &stats))
298 errorMsg("fstat error");
300 /* Use file_lines only if FD refers to a regular file with
301 its file pointer positioned at beginning of file. */
302 /* FIXME: adding the lseek conjunct is a kludge.
303 Once there's a reasonable test suite, fix the true culprit:
304 file_lines. file_lines shouldn't presume that the input
305 file pointer is initially positioned to beginning of file. */
306 if (S_ISREG(stats.st_mode)
307 && lseek(fd, (off_t) 0, SEEK_CUR) == (off_t) 0) {
308 length = lseek(fd, (off_t) 0, SEEK_END);
309 if (length != 0 && file_lines(filename, fd, n_lines, length))
311 dump_remainder(filename, fd);
313 return pipe_lines(filename, fd, n_lines);
318 /* Display the last N_UNITS lines of file FILENAME.
319 "-" for FILENAME means the standard input.
320 Return 0 if successful, 1 if an error occurred. */
322 static int tail_file(const char *filename, off_t n_units)
326 if (!strcmp(filename, "-")) {
327 filename = "standard input";
328 errors = tail_lines(filename, 0, (long) n_units);
330 /* Not standard input. */
331 fd = open(filename, O_RDONLY);
333 fatalError("open error");
335 errors = tail_lines(filename, fd, (long) n_units);
342 extern int tail_main(int argc, char **argv)
345 int n_units = DEFAULT_N_LINES;
349 forever = print_headers = 0;
352 for (i = 1; i < argc; i++) {
353 if (argv[i][0] == '-') {
362 n_tmp = atoi(argv[i]);
371 fprintf(stderr, "tail: invalid option -- %c\n", opt);
382 "tail: option -f is invalid with multiple files\n");
389 exit_status |= tail_file("-", n_units);
391 for (; i < argc; i++)
392 exit_status |= tail_file(argv[i], n_units);
395 exit(exit_status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
400 // Here follows the code for the full featured tail code
403 /* tail -- output the last part of file(s)
404 Copyright (C) 89, 90, 91, 95, 1996 Free Software Foundation, Inc.
406 This program is free software; you can redistribute it and/or modify
407 it under the terms of the GNU General Public License as published by
408 the Free Software Foundation; either version 2, or (at your option)
411 This program is distributed in the hope that it will be useful,
412 but WITHOUT ANY WARRANTY; without even the implied warranty of
413 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
414 GNU General Public License for more details.
416 You should have received a copy of the GNU General Public License
417 along with this program; if not, write to the Free Software
418 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
420 Original version by Paul Rubin <phr@ocf.berkeley.edu>.
421 Extensions by David MacKenzie <djm@gnu.ai.mit.edu>.
422 tail -f for multiple files by Ian Lance Taylor <ian@airs.com>.
424 Rewrote the option parser, removed locales support,
425 and generally busyboxed, Erik Andersen <andersen@lineo.com>
429 #include "internal.h"
435 #include <sys/types.h>
436 #include <sys/types.h>
437 #include <sys/stat.h>
443 /* Disable assertions. Some systems have broken assert macros. */
447 static void detailed_error(int i, int errnum, char *fmt, ...)
451 va_start(arguments, fmt);
452 vfprintf(stderr, fmt, arguments);
453 fprintf(stderr, "\n%s\n", strerror(errnum));
459 #define XWRITE(fd, buffer, n_bytes) \
462 assert ((fd) == 1); \
463 assert ((n_bytes) >= 0); \
464 if (n_bytes > 0 && fwrite ((buffer), 1, (n_bytes), stdout) == 0) \
465 detailed_error (EXIT_FAILURE, errno, "write error"); \
469 /* Number of items to tail. */
470 #define DEFAULT_N_LINES 10
472 /* Size of atomic reads. */
474 #define BUFSIZ (512 * 8)
477 /* If nonzero, interpret the numeric argument as the number of lines.
478 Otherwise, interpret it as the number of bytes. */
479 static int count_lines;
481 /* If nonzero, read from the end of one file until killed. */
484 /* If nonzero, read from the end of multiple files until killed. */
485 static int forever_multiple;
487 /* Array of file descriptors if forever_multiple is 1. */
488 static int *file_descs;
490 /* Array of file sizes if forever_multiple is 1. */
491 static off_t *file_sizes;
493 /* If nonzero, count from start of file instead of end. */
494 static int from_start;
496 /* If nonzero, print filename headers. */
497 static int print_headers;
499 /* When to print the filename banners. */
501 multiple_files, always, never
504 /* The name this program was run with. */
507 /* Nonzero if we have ever read standard input. */
508 static int have_read_stdin;
511 static const char tail_usage[] = "tail [OPTION]... [FILE]...\n\
513 Print last 10 lines of each FILE to standard output.\n\
514 With more than one FILE, precede each with a header giving the file name.\n\
515 With no FILE, or when FILE is -, read standard input.\n\
517 -c=N[kbm] output the last N bytes\n\
518 -f output appended data as the file grows\n\
519 -n=N output the last N lines, instead of last 10\n\
520 -q never output headers giving file names\n\
521 -v always output headers giving file names\n\
522 --help display this help and exit\n\
524 If the first character of N (bytes or lines) is a `+', output begins with \n\
525 the Nth item from the start of each file, otherwise, print the last N items\n\
526 in the file. N bytes may be suffixed by k (x1024), b (x512), or m (1024^2).\n\n";
528 static void write_header(const char *filename, const char *comment)
530 static int first_file = 1;
532 printf("%s==> %s%s%s <==\n", (first_file ? "" : "\n"), filename,
533 (comment ? ": " : ""), (comment ? comment : ""));
537 /* Print the last N_LINES lines from the end of file FD.
538 Go backward through the file, reading `BUFSIZ' bytes at a time (except
539 probably the first), until we hit the start of the file or have
540 read NUMBER newlines.
541 POS starts out as the length of the file (the offset of the last
542 byte of the file + 1).
543 Return 0 if successful, 1 if an error occurred. */
546 file_lines(const char *filename, int fd, long int n_lines, off_t pos)
550 int i; /* Index into `buffer' for scanning. */
555 /* Set `bytes_read' to the size of the last, probably partial, buffer;
556 0 < `bytes_read' <= `BUFSIZ'. */
557 bytes_read = pos % BUFSIZ;
560 /* Make `pos' a multiple of `BUFSIZ' (0 if the file is short), so that all
561 reads will be on block boundaries, which might increase efficiency. */
563 lseek(fd, pos, SEEK_SET);
564 bytes_read = fullRead(fd, buffer, bytes_read);
565 if (bytes_read == -1) {
566 detailed_error(0, errno, "%s", filename);
570 /* Count the incomplete line on files that don't end with a newline. */
571 if (bytes_read && buffer[bytes_read - 1] != '\n')
575 /* Scan backward, counting the newlines in this bufferfull. */
576 for (i = bytes_read - 1; i >= 0; i--) {
577 /* Have we counted the requested number of newlines yet? */
578 if (buffer[i] == '\n' && n_lines-- == 0) {
579 /* If this newline wasn't the last character in the buffer,
580 print the text after it. */
581 if (i != bytes_read - 1)
582 XWRITE(STDOUT_FILENO, &buffer[i + 1],
583 bytes_read - (i + 1));
587 /* Not enough newlines in that bufferfull. */
589 /* Not enough lines in the file; print the entire file. */
590 lseek(fd, (off_t) 0, SEEK_SET);
594 lseek(fd, pos, SEEK_SET);
596 while ((bytes_read = fullRead(fd, buffer, BUFSIZ)) > 0);
597 if (bytes_read == -1) {
598 detailed_error(0, errno, "%s", filename);
604 /* Print the last N_LINES lines from the end of the standard input,
605 open for reading as pipe FD.
606 Buffer the text as a linked list of LBUFFERs, adding them as needed.
607 Return 0 if successful, 1 if an error occured. */
609 static int pipe_lines(const char *filename, int fd, long int n_lines)
614 struct linebuffer *next;
616 typedef struct linebuffer LBUFFER;
617 LBUFFER *first, *last, *tmp;
618 int i; /* Index into buffers. */
619 int total_lines = 0; /* Total number of newlines in all buffers. */
622 first = last = (LBUFFER *) xmalloc(sizeof(LBUFFER));
623 first->nbytes = first->nlines = 0;
625 tmp = (LBUFFER *) xmalloc(sizeof(LBUFFER));
627 /* Input is always read into a fresh buffer. */
628 while ((tmp->nbytes = fullRead(fd, tmp->buffer, BUFSIZ)) > 0) {
632 /* Count the number of newlines just read. */
633 for (i = 0; i < tmp->nbytes; i++)
634 if (tmp->buffer[i] == '\n')
636 total_lines += tmp->nlines;
638 /* If there is enough room in the last buffer read, just append the new
639 one to it. This is because when reading from a pipe, `nbytes' can
640 often be very small. */
641 if (tmp->nbytes + last->nbytes < BUFSIZ) {
642 memcpy(&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes);
643 last->nbytes += tmp->nbytes;
644 last->nlines += tmp->nlines;
646 /* If there's not enough room, link the new buffer onto the end of
647 the list, then either free up the oldest buffer for the next
648 read if that would leave enough lines, or else malloc a new one.
649 Some compaction mechanism is possible but probably not
651 last = last->next = tmp;
652 if (total_lines - first->nlines > n_lines) {
654 total_lines -= first->nlines;
657 tmp = (LBUFFER *) xmalloc(sizeof(LBUFFER));
660 if (tmp->nbytes == -1) {
661 detailed_error(0, errno, "%s", filename);
669 /* This prevents a core dump when the pipe contains no newlines. */
673 /* Count the incomplete line on files that don't end with a newline. */
674 if (last->buffer[last->nbytes - 1] != '\n') {
679 /* Run through the list, printing lines. First, skip over unneeded
681 for (tmp = first; total_lines - tmp->nlines > n_lines; tmp = tmp->next)
682 total_lines -= tmp->nlines;
684 /* Find the correct beginning, then print the rest of the file. */
685 if (total_lines > n_lines) {
688 /* Skip `total_lines' - `n_lines' newlines. We made sure that
689 `total_lines' - `n_lines' <= `tmp->nlines'. */
691 for (i = total_lines - n_lines; i; --i)
692 while (*cp++ != '\n')
694 i = cp - tmp->buffer;
697 XWRITE(STDOUT_FILENO, &tmp->buffer[i], tmp->nbytes - i);
699 for (tmp = tmp->next; tmp; tmp = tmp->next)
700 XWRITE(STDOUT_FILENO, tmp->buffer, tmp->nbytes);
705 free((char *) first);
711 /* Print the last N_BYTES characters from the end of pipe FD.
712 This is a stripped down version of pipe_lines.
713 Return 0 if successful, 1 if an error occurred. */
715 static int pipe_bytes(const char *filename, int fd, off_t n_bytes)
720 struct charbuffer *next;
722 typedef struct charbuffer CBUFFER;
723 CBUFFER *first, *last, *tmp;
724 int i; /* Index into buffers. */
725 int total_bytes = 0; /* Total characters in all buffers. */
728 first = last = (CBUFFER *) xmalloc(sizeof(CBUFFER));
731 tmp = (CBUFFER *) xmalloc(sizeof(CBUFFER));
733 /* Input is always read into a fresh buffer. */
734 while ((tmp->nbytes = fullRead(fd, tmp->buffer, BUFSIZ)) > 0) {
737 total_bytes += tmp->nbytes;
738 /* If there is enough room in the last buffer read, just append the new
739 one to it. This is because when reading from a pipe, `nbytes' can
740 often be very small. */
741 if (tmp->nbytes + last->nbytes < BUFSIZ) {
742 memcpy(&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes);
743 last->nbytes += tmp->nbytes;
745 /* If there's not enough room, link the new buffer onto the end of
746 the list, then either free up the oldest buffer for the next
747 read if that would leave enough characters, or else malloc a new
748 one. Some compaction mechanism is possible but probably not
750 last = last->next = tmp;
751 if (total_bytes - first->nbytes > n_bytes) {
753 total_bytes -= first->nbytes;
756 tmp = (CBUFFER *) xmalloc(sizeof(CBUFFER));
760 if (tmp->nbytes == -1) {
761 detailed_error(0, errno, "%s", filename);
769 /* Run through the list, printing characters. First, skip over unneeded
771 for (tmp = first; total_bytes - tmp->nbytes > n_bytes; tmp = tmp->next)
772 total_bytes -= tmp->nbytes;
774 /* Find the correct beginning, then print the rest of the file.
775 We made sure that `total_bytes' - `n_bytes' <= `tmp->nbytes'. */
776 if (total_bytes > n_bytes)
777 i = total_bytes - n_bytes;
780 XWRITE(STDOUT_FILENO, &tmp->buffer[i], tmp->nbytes - i);
782 for (tmp = tmp->next; tmp; tmp = tmp->next)
783 XWRITE(STDOUT_FILENO, tmp->buffer, tmp->nbytes);
788 free((char *) first);
794 /* Skip N_BYTES characters from the start of pipe FD, and print
795 any extra characters that were read beyond that.
796 Return 1 on error, 0 if ok. */
798 static int start_bytes(const char *filename, int fd, off_t n_bytes)
803 while (n_bytes > 0 && (bytes_read = fullRead(fd, buffer, BUFSIZ)) > 0)
804 n_bytes -= bytes_read;
805 if (bytes_read == -1) {
806 detailed_error(0, errno, "%s", filename);
808 } else if (n_bytes < 0)
809 XWRITE(STDOUT_FILENO, &buffer[bytes_read + n_bytes], -n_bytes);
813 /* Skip N_LINES lines at the start of file or pipe FD, and print
814 any extra characters that were read beyond that.
815 Return 1 on error, 0 if ok. */
817 static int start_lines(const char *filename, int fd, long int n_lines)
821 int bytes_to_skip = 0;
823 while (n_lines && (bytes_read = fullRead(fd, buffer, BUFSIZ)) > 0) {
825 while (bytes_to_skip < bytes_read)
826 if (buffer[bytes_to_skip++] == '\n' && --n_lines == 0)
829 if (bytes_read == -1) {
830 detailed_error(0, errno, "%s", filename);
832 } else if (bytes_to_skip < bytes_read) {
833 XWRITE(STDOUT_FILENO, &buffer[bytes_to_skip],
834 bytes_read - bytes_to_skip);
839 /* Display file FILENAME from the current position in FD to the end.
840 If `forever' is nonzero, keep reading from the end of the file
841 until killed. Return the number of bytes read from the file. */
843 static long dump_remainder(const char *filename, int fd)
851 while ((bytes_read = fullRead(fd, buffer, BUFSIZ)) > 0) {
852 XWRITE(STDOUT_FILENO, buffer, bytes_read);
855 if (bytes_read == -1)
856 detailed_error(EXIT_FAILURE, errno, "%s", filename);
862 if (forever_multiple)
869 /* Tail NFILES (>1) files forever until killed. The file names are in
870 NAMES. The open file descriptors are in `file_descs', and the size
871 at which we stopped tailing them is in `file_sizes'. We loop over
872 each of them, doing an fstat to see if they have changed size. If
873 none of them have changed size in one iteration, we sleep for a
874 second and try again. We do this until the user interrupts us. */
876 static void tail_forever(char **names, int nfiles)
887 for (i = 0; i < nfiles; i++) {
890 if (file_descs[i] < 0)
892 if (fstat(file_descs[i], &stats) < 0) {
893 detailed_error(0, errno, "%s", names[i]);
897 if (stats.st_size == file_sizes[i])
900 /* This file has changed size. Print out what we can, and
901 then keep looping. */
905 if (stats.st_size < file_sizes[i]) {
906 write_header(names[i], "file truncated");
908 lseek(file_descs[i], stats.st_size, SEEK_SET);
909 file_sizes[i] = stats.st_size;
915 write_header(names[i], NULL);
918 file_sizes[i] += dump_remainder(names[i], file_descs[i]);
921 /* If none of the files changed size, sleep. */
927 /* Output the last N_BYTES bytes of file FILENAME open for reading in FD.
928 Return 0 if successful, 1 if an error occurred. */
930 static int tail_bytes(const char *filename, int fd, off_t n_bytes)
934 /* FIXME: resolve this like in dd.c. */
935 /* Use fstat instead of checking for errno == ESPIPE because
936 lseek doesn't work on some special files but doesn't return an
938 if (fstat(fd, &stats)) {
939 detailed_error(0, errno, "%s", filename);
944 if (S_ISREG(stats.st_mode))
945 lseek(fd, n_bytes, SEEK_CUR);
946 else if (start_bytes(filename, fd, n_bytes))
948 dump_remainder(filename, fd);
950 if (S_ISREG(stats.st_mode)) {
951 off_t current_pos, end_pos;
952 size_t bytes_remaining;
954 if ((current_pos = lseek(fd, (off_t) 0, SEEK_CUR)) != -1
955 && (end_pos = lseek(fd, (off_t) 0, SEEK_END)) != -1) {
958 /* Be careful here. The current position may actually be
959 beyond the end of the file. */
960 bytes_remaining = (diff =
961 end_pos - current_pos) < 0 ? 0 : diff;
963 detailed_error(0, errno, "%s", filename);
967 if (bytes_remaining <= n_bytes) {
968 /* From the current position to end of file, there are no
969 more bytes than have been requested. So reposition the
970 file pointer to the incoming current position and print
971 everything after that. */
972 lseek(fd, current_pos, SEEK_SET);
974 /* There are more bytes remaining than were requested.
976 lseek(fd, -n_bytes, SEEK_END);
978 dump_remainder(filename, fd);
980 return pipe_bytes(filename, fd, n_bytes);
985 /* Output the last N_LINES lines of file FILENAME open for reading in FD.
986 Return 0 if successful, 1 if an error occurred. */
988 static int tail_lines(const char *filename, int fd, long int n_lines)
993 if (fstat(fd, &stats)) {
994 detailed_error(0, errno, "%s", filename);
999 if (start_lines(filename, fd, n_lines))
1001 dump_remainder(filename, fd);
1003 /* Use file_lines only if FD refers to a regular file with
1004 its file pointer positioned at beginning of file. */
1005 /* FIXME: adding the lseek conjunct is a kludge.
1006 Once there's a reasonable test suite, fix the true culprit:
1007 file_lines. file_lines shouldn't presume that the input
1008 file pointer is initially positioned to beginning of file. */
1009 if (S_ISREG(stats.st_mode)
1010 && lseek(fd, (off_t) 0, SEEK_CUR) == (off_t) 0) {
1011 length = lseek(fd, (off_t) 0, SEEK_END);
1012 if (length != 0 && file_lines(filename, fd, n_lines, length))
1014 dump_remainder(filename, fd);
1016 return pipe_lines(filename, fd, n_lines);
1021 /* Display the last N_UNITS units of file FILENAME, open for reading
1023 Return 0 if successful, 1 if an error occurred. */
1025 static int tail(const char *filename, int fd, off_t n_units)
1028 return tail_lines(filename, fd, (long) n_units);
1030 return tail_bytes(filename, fd, n_units);
1033 /* Display the last N_UNITS units of file FILENAME.
1034 "-" for FILENAME means the standard input.
1035 FILENUM is this file's index in the list of files the user gave.
1036 Return 0 if successful, 1 if an error occurred. */
1038 static int tail_file(const char *filename, off_t n_units, int filenum)
1043 if (!strcmp(filename, "-")) {
1044 have_read_stdin = 1;
1045 filename = "standard input";
1047 write_header(filename, NULL);
1048 errors = tail(filename, 0, n_units);
1049 if (forever_multiple) {
1050 if (fstat(0, &stats) < 0) {
1051 detailed_error(0, errno, "standard input");
1053 } else if (!S_ISREG(stats.st_mode)) {
1054 detailed_error(0, 0,
1055 "standard input: cannot follow end of non-regular file");
1059 file_descs[filenum] = -1;
1061 file_descs[filenum] = 0;
1062 file_sizes[filenum] = stats.st_size;
1066 /* Not standard input. */
1067 fd = open(filename, O_RDONLY);
1069 if (forever_multiple)
1070 file_descs[filenum] = -1;
1071 detailed_error(0, errno, "%s", filename);
1075 write_header(filename, NULL);
1076 errors = tail(filename, fd, n_units);
1077 if (forever_multiple) {
1078 if (fstat(fd, &stats) < 0) {
1079 detailed_error(0, errno, "%s", filename);
1081 } else if (!S_ISREG(stats.st_mode)) {
1082 detailed_error(0, 0,
1083 "%s: cannot follow end of non-regular file",
1089 file_descs[filenum] = -1;
1091 file_descs[filenum] = fd;
1092 file_sizes[filenum] = stats.st_size;
1096 detailed_error(0, errno, "%s", filename);
1106 extern int tail_main(int argc, char **argv)
1109 enum header_mode header_mode = multiple_files;
1110 int exit_status = 0;
1112 /* If from_start, the number of items to skip before printing; otherwise,
1113 the number of items at the end of the file to print. Initially, -1
1114 means the value has not been set. */
1119 program_name = argv[0];
1120 have_read_stdin = 0;
1122 forever = forever_multiple = from_start = print_headers = 0;
1124 /* Parse any options */
1125 //fprintf(stderr, "argc=%d, argv=%s\n", argc, *argv);
1126 while (--argc > 0 && (**(++argv) == '-' || **argv == '+')) {
1127 if (**argv == '+') {
1131 while (stopit == 0 && *(++(*argv))) {
1139 n_units = getNum(*(++argv));
1153 n_units = atol(*(++argv));
1158 header_mode = never;
1162 header_mode = always;
1173 n_units = DEFAULT_N_LINES;
1175 /* To start printing with item N_UNITS from the start of the file, skip
1176 N_UNITS - 1 items. `tail +0' is actually meaningless, but for Unix
1177 compatibility it's treated the same as `tail +1'. */
1186 if (n_files > 1 && forever) {
1187 forever_multiple = 1;
1189 file_descs = (int *) xmalloc(n_files * sizeof(int));
1191 file_sizes = (off_t *) xmalloc(n_files * sizeof(off_t));
1194 if (header_mode == always
1195 || (header_mode == multiple_files && n_files > 1))
1199 exit_status |= tail_file("-", n_units, 0);
1203 for (i = 0; i < n_files; i++)
1204 exit_status |= tail_file(file[i], n_units, i);
1206 if (forever_multiple)
1207 tail_forever(file, n_files);
1210 if (have_read_stdin && close(0) < 0)
1211 detailed_error(EXIT_FAILURE, errno, "-");
1212 if (fclose(stdout) == EOF)
1213 detailed_error(EXIT_FAILURE, errno, "write error");
1214 exit(exit_status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);