1 /* tail -- output the last part of file(s)
2 Copyright (C) 1989-1991, 1995-2006, 2008-2011 Free Software Foundation, Inc.
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation, either version 3 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <http://www.gnu.org/licenses/>. */
17 /* Can display any amount of data, unlike the Unix version, which uses
18 a fixed size buffer and therefore can only deliver a limited number
21 Original version by Paul Rubin <phr@ocf.berkeley.edu>.
22 Extensions by David MacKenzie <djm@gnu.ai.mit.edu>.
23 tail -f for multiple files by Ian Lance Taylor <ian@airs.com>.
24 inotify back-end by Giuseppe Scrivano <gscrivano@gnu.org>. */
31 #include <sys/types.h>
42 #include "safe-read.h"
43 #include "stat-time.h"
45 #include "xnanosleep.h"
51 # include <sys/inotify.h>
52 /* `select' is used by tail_forever_inotify. */
53 # include <sys/select.h>
55 /* inotify needs to know if a file is local. */
57 # if HAVE_SYS_STATFS_H
58 # include <sys/statfs.h>
64 /* The official name of this program (e.g., no `g' prefix). */
65 #define PROGRAM_NAME "tail"
68 proper_name ("Paul Rubin"), \
69 proper_name ("David MacKenzie"), \
70 proper_name ("Ian Lance Taylor"), \
71 proper_name ("Jim Meyering")
73 /* Number of items to tail. */
74 #define DEFAULT_N_LINES 10
76 /* Special values for dump_remainder's N_BYTES parameter. */
77 #define COPY_TO_EOF UINTMAX_MAX
78 #define COPY_A_BUFFER (UINTMAX_MAX - 1)
80 /* FIXME: make Follow_name the default? */
81 #define DEFAULT_FOLLOW_MODE Follow_descriptor
85 /* Follow the name of each file: if the file is renamed, try to reopen
86 that name and track the end of the new file if/when it's recreated.
87 This is useful for tracking logs that are occasionally rotated. */
90 /* Follow each descriptor obtained upon opening a file.
91 That means we'll continue to follow the end of a file even after
92 it has been renamed or unlinked. */
96 /* The types of files for which tail works. */
97 #define IS_TAILABLE_FILE_TYPE(Mode) \
98 (S_ISREG (Mode) || S_ISFIFO (Mode) || S_ISSOCK (Mode) || S_ISCHR (Mode))
100 static char const *const follow_mode_string
[] =
102 "descriptor", "name", NULL
105 static enum Follow_mode
const follow_mode_map
[] =
107 Follow_descriptor
, Follow_name
,
112 /* The actual file name, or "-" for stdin. */
115 /* Attributes of the file the last time we checked. */
117 struct timespec mtime
;
122 /* The specified name initially referred to a directory or some other
123 type for which tail isn't meaningful. Unlike for a permission problem
124 (tailable, below) once this is set, the name is not checked ever again. */
127 /* See the description of fremote. */
130 /* A file is tailable if it exists, is readable, and is of type
131 IS_TAILABLE_FILE_TYPE. */
134 /* File descriptor on which the file is open; -1 if it's not open. */
137 /* The value of errno seen last time we checked this file. */
140 /* 1 if O_NONBLOCK is clear, 0 if set, -1 if not known. */
144 /* The watch descriptor used by inotify. */
147 /* The parent directory watch descriptor. It is used only
148 * when Follow_name is used. */
151 /* Offset in NAME of the basename part. */
152 size_t basename_start
;
155 /* See description of DEFAULT_MAX_N_... below. */
156 uintmax_t n_unchanged_stats
;
160 /* The events mask used with inotify on files. This mask is not used on
162 static const uint32_t inotify_wd_mask
= (IN_MODIFY
| IN_ATTRIB
163 | IN_DELETE_SELF
| IN_MOVE_SELF
);
166 /* Keep trying to open a file even if it is inaccessible when tail starts
167 or if it becomes inaccessible later -- useful only with -f. */
168 static bool reopen_inaccessible_files
;
170 /* If true, interpret the numeric argument as the number of lines.
171 Otherwise, interpret it as the number of bytes. */
172 static bool count_lines
;
174 /* Whether we follow the name of each file or the file descriptor
175 that is initially associated with each name. */
176 static enum Follow_mode follow_mode
= Follow_descriptor
;
178 /* If true, read from the ends of all specified files until killed. */
181 /* If true, count from start of file instead of end. */
182 static bool from_start
;
184 /* If true, print filename headers. */
185 static bool print_headers
;
187 /* When to print the filename banners. */
190 multiple_files
, always
, never
193 /* When tailing a file by name, if there have been this many consecutive
194 iterations for which the file has not changed, then open/fstat
195 the file to determine if that file name is still associated with the
196 same device/inode-number pair as before. This option is meaningful only
197 when following by name. --max-unchanged-stats=N */
198 #define DEFAULT_MAX_N_UNCHANGED_STATS_BETWEEN_OPENS 5
199 static uintmax_t max_n_unchanged_stats_between_opens
=
200 DEFAULT_MAX_N_UNCHANGED_STATS_BETWEEN_OPENS
;
202 /* The process ID of the process (presumably on the current host)
203 that is writing to all followed files. */
206 /* True if we have ever read standard input. */
207 static bool have_read_stdin
;
209 /* If nonzero, skip the is-regular-file test used to determine whether
210 to use the lseek optimization. Instead, use the more general (and
211 more expensive) code unconditionally. Intended solely for testing. */
212 static bool presume_input_pipe
;
214 /* If nonzero then don't use inotify even if available. */
215 static bool disable_inotify
;
217 /* For long options that have no equivalent short option, use a
218 non-character as a pseudo short option, starting with CHAR_MAX + 1. */
221 RETRY_OPTION
= CHAR_MAX
+ 1,
222 MAX_UNCHANGED_STATS_OPTION
,
224 PRESUME_INPUT_PIPE_OPTION
,
226 DISABLE_INOTIFY_OPTION
229 static struct option
const long_options
[] =
231 {"bytes", required_argument
, NULL
, 'c'},
232 {"follow", optional_argument
, NULL
, LONG_FOLLOW_OPTION
},
233 {"lines", required_argument
, NULL
, 'n'},
234 {"max-unchanged-stats", required_argument
, NULL
, MAX_UNCHANGED_STATS_OPTION
},
235 {"-disable-inotify", no_argument
, NULL
,
236 DISABLE_INOTIFY_OPTION
}, /* do not document */
237 {"pid", required_argument
, NULL
, PID_OPTION
},
238 {"-presume-input-pipe", no_argument
, NULL
,
239 PRESUME_INPUT_PIPE_OPTION
}, /* do not document */
240 {"quiet", no_argument
, NULL
, 'q'},
241 {"retry", no_argument
, NULL
, RETRY_OPTION
},
242 {"silent", no_argument
, NULL
, 'q'},
243 {"sleep-interval", required_argument
, NULL
, 's'},
244 {"verbose", no_argument
, NULL
, 'v'},
245 {GETOPT_HELP_OPTION_DECL
},
246 {GETOPT_VERSION_OPTION_DECL
},
253 if (status
!= EXIT_SUCCESS
)
254 fprintf (stderr
, _("Try `%s --help' for more information.\n"),
259 Usage: %s [OPTION]... [FILE]...\n\
263 Print the last %d lines of each FILE to standard output.\n\
264 With more than one FILE, precede each with a header giving the file name.\n\
265 With no FILE, or when FILE is -, read standard input.\n\
267 "), DEFAULT_N_LINES
);
269 Mandatory arguments to long options are mandatory for short options too.\n\
272 -c, --bytes=K output the last K bytes; alternatively, use -c +K\n\
273 to output bytes starting with the Kth of each file\n\
276 -f, --follow[={name|descriptor}]\n\
277 output appended data as the file grows;\n\
278 -f, --follow, and --follow=descriptor are\n\
280 -F same as --follow=name --retry\n\
283 -n, --lines=K output the last K lines, instead of the last %d;\n\
284 or use -n +K to output lines starting with the Kth\n\
285 --max-unchanged-stats=N\n\
286 with --follow=name, reopen a FILE which has not\n\
287 changed size after N (default %d) iterations\n\
288 to see if it has been unlinked or renamed\n\
289 (this is the usual case of rotated log files).\n\
290 With inotify, this option is rarely useful.\n\
293 DEFAULT_MAX_N_UNCHANGED_STATS_BETWEEN_OPENS
296 --pid=PID with -f, terminate after process ID, PID dies\n\
297 -q, --quiet, --silent never output headers giving file names\n\
298 --retry keep trying to open a file even when it is or\n\
299 becomes inaccessible; useful when following by\n\
300 name, i.e., with --follow=name\n\
303 -s, --sleep-interval=N with -f, sleep for approximately N seconds\n\
304 (default 1.0) between iterations.\n\
305 With inotify and --pid=P, check process P at\n\
306 least once every N seconds.\n\
307 -v, --verbose always output headers giving file names\n\
309 fputs (HELP_OPTION_DESCRIPTION
, stdout
);
310 fputs (VERSION_OPTION_DESCRIPTION
, stdout
);
313 If the first character of K (the number of bytes or lines) is a `+',\n\
314 print beginning with the Kth item from the start of each file, otherwise,\n\
315 print the last K items in the file. K may have a multiplier suffix:\n\
316 b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024,\n\
317 GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.\n\
321 With --follow (-f), tail defaults to following the file descriptor, which\n\
322 means that even if a tail'ed file is renamed, tail will continue to track\n\
323 its end. This default behavior is not desirable when you really want to\n\
324 track the actual name of the file, not the file descriptor (e.g., log\n\
325 rotation). Use --follow=name in that case. That causes tail to track the\n\
326 named file in a way that accommodates renaming, removal and creation.\n\
328 emit_ancillary_info ();
334 valid_file_spec (struct File_spec
const *f
)
336 /* Exactly one of the following subexpressions must be true. */
337 return ((f
->fd
== -1) ^ (f
->errnum
== 0));
341 pretty_name (struct File_spec
const *f
)
343 return (STREQ (f
->name
, "-") ? _("standard input") : f
->name
);
347 xwrite_stdout (char const *buffer
, size_t n_bytes
)
349 if (n_bytes
> 0 && fwrite (buffer
, 1, n_bytes
, stdout
) == 0)
350 error (EXIT_FAILURE
, errno
, _("write error"));
353 /* Record a file F with descriptor FD, size SIZE, status ST, and
354 blocking status BLOCKING. */
357 record_open_fd (struct File_spec
*f
, int fd
,
358 off_t size
, struct stat
const *st
,
363 f
->mtime
= get_stat_mtime (st
);
366 f
->mode
= st
->st_mode
;
367 f
->blocking
= blocking
;
368 f
->n_unchanged_stats
= 0;
372 /* Close the file with descriptor FD and name FILENAME. */
375 close_fd (int fd
, const char *filename
)
377 if (fd
!= -1 && fd
!= STDIN_FILENO
&& close (fd
))
379 error (0, errno
, _("closing %s (fd=%d)"), filename
, fd
);
384 write_header (const char *pretty_filename
)
386 static bool first_file
= true;
388 printf ("%s==> %s <==\n", (first_file
? "" : "\n"), pretty_filename
);
392 /* Read and output N_BYTES of file PRETTY_FILENAME starting at the current
393 position in FD. If N_BYTES is COPY_TO_EOF, then copy until end of file.
394 If N_BYTES is COPY_A_BUFFER, then copy at most one buffer's worth.
395 Return the number of bytes read from the file. */
398 dump_remainder (const char *pretty_filename
, int fd
, uintmax_t n_bytes
)
401 uintmax_t n_remaining
= n_bytes
;
407 size_t n
= MIN (n_remaining
, BUFSIZ
);
408 size_t bytes_read
= safe_read (fd
, buffer
, n
);
409 if (bytes_read
== SAFE_READ_ERROR
)
412 error (EXIT_FAILURE
, errno
, _("error reading %s"),
413 quote (pretty_filename
));
418 xwrite_stdout (buffer
, bytes_read
);
419 n_written
+= bytes_read
;
420 if (n_bytes
!= COPY_TO_EOF
)
422 n_remaining
-= bytes_read
;
423 if (n_remaining
== 0 || n_bytes
== COPY_A_BUFFER
)
431 /* Call lseek with the specified arguments, where file descriptor FD
432 corresponds to the file, FILENAME.
433 Give a diagnostic and exit nonzero if lseek fails.
434 Otherwise, return the resulting offset. */
437 xlseek (int fd
, off_t offset
, int whence
, char const *filename
)
439 off_t new_offset
= lseek (fd
, offset
, whence
);
440 char buf
[INT_BUFSIZE_BOUND (offset
)];
446 s
= offtostr (offset
, buf
);
450 error (0, errno
, _("%s: cannot seek to offset %s"),
454 error (0, errno
, _("%s: cannot seek to relative offset %s"),
458 error (0, errno
, _("%s: cannot seek to end-relative offset %s"),
468 /* Print the last N_LINES lines from the end of file FD.
469 Go backward through the file, reading `BUFSIZ' bytes at a time (except
470 probably the first), until we hit the start of the file or have
471 read NUMBER newlines.
472 START_POS is the starting position of the read pointer for the file
473 associated with FD (may be nonzero).
474 END_POS is the file offset of EOF (one larger than offset of last byte).
475 Return true if successful. */
478 file_lines (const char *pretty_filename
, int fd
, uintmax_t n_lines
,
479 off_t start_pos
, off_t end_pos
, uintmax_t *read_pos
)
488 /* Set `bytes_read' to the size of the last, probably partial, buffer;
489 0 < `bytes_read' <= `BUFSIZ'. */
490 bytes_read
= (pos
- start_pos
) % BUFSIZ
;
493 /* Make `pos' a multiple of `BUFSIZ' (0 if the file is short), so that all
494 reads will be on block boundaries, which might increase efficiency. */
496 xlseek (fd
, pos
, SEEK_SET
, pretty_filename
);
497 bytes_read
= safe_read (fd
, buffer
, bytes_read
);
498 if (bytes_read
== SAFE_READ_ERROR
)
500 error (0, errno
, _("error reading %s"), quote (pretty_filename
));
503 *read_pos
= pos
+ bytes_read
;
505 /* Count the incomplete line on files that don't end with a newline. */
506 if (bytes_read
&& buffer
[bytes_read
- 1] != '\n')
511 /* Scan backward, counting the newlines in this bufferfull. */
513 size_t n
= bytes_read
;
517 nl
= memrchr (buffer
, '\n', n
);
523 /* If this newline isn't the last character in the buffer,
524 output the part that is after it. */
525 if (n
!= bytes_read
- 1)
526 xwrite_stdout (nl
+ 1, bytes_read
- (n
+ 1));
527 *read_pos
+= dump_remainder (pretty_filename
, fd
,
528 end_pos
- (pos
+ bytes_read
));
533 /* Not enough newlines in that bufferfull. */
534 if (pos
== start_pos
)
536 /* Not enough lines in the file; print everything from
537 start_pos to the end. */
538 xlseek (fd
, start_pos
, SEEK_SET
, pretty_filename
);
539 *read_pos
= start_pos
+ dump_remainder (pretty_filename
, fd
,
544 xlseek (fd
, pos
, SEEK_SET
, pretty_filename
);
546 bytes_read
= safe_read (fd
, buffer
, BUFSIZ
);
547 if (bytes_read
== SAFE_READ_ERROR
)
549 error (0, errno
, _("error reading %s"), quote (pretty_filename
));
553 *read_pos
= pos
+ bytes_read
;
555 while (bytes_read
> 0);
560 /* Print the last N_LINES lines from the end of the standard input,
561 open for reading as pipe FD.
562 Buffer the text as a linked list of LBUFFERs, adding them as needed.
563 Return true if successful. */
566 pipe_lines (const char *pretty_filename
, int fd
, uintmax_t n_lines
,
574 struct linebuffer
*next
;
576 typedef struct linebuffer LBUFFER
;
577 LBUFFER
*first
, *last
, *tmp
;
578 size_t total_lines
= 0; /* Total number of newlines in all buffers. */
580 size_t n_read
; /* Size in bytes of most recent read */
582 first
= last
= xmalloc (sizeof (LBUFFER
));
583 first
->nbytes
= first
->nlines
= 0;
585 tmp
= xmalloc (sizeof (LBUFFER
));
587 /* Input is always read into a fresh buffer. */
590 n_read
= safe_read (fd
, tmp
->buffer
, BUFSIZ
);
591 if (n_read
== 0 || n_read
== SAFE_READ_ERROR
)
593 tmp
->nbytes
= n_read
;
598 /* Count the number of newlines just read. */
600 char const *buffer_end
= tmp
->buffer
+ n_read
;
601 char const *p
= tmp
->buffer
;
602 while ((p
= memchr (p
, '\n', buffer_end
- p
)))
608 total_lines
+= tmp
->nlines
;
610 /* If there is enough room in the last buffer read, just append the new
611 one to it. This is because when reading from a pipe, `n_read' can
612 often be very small. */
613 if (tmp
->nbytes
+ last
->nbytes
< BUFSIZ
)
615 memcpy (&last
->buffer
[last
->nbytes
], tmp
->buffer
, tmp
->nbytes
);
616 last
->nbytes
+= tmp
->nbytes
;
617 last
->nlines
+= tmp
->nlines
;
621 /* If there's not enough room, link the new buffer onto the end of
622 the list, then either free up the oldest buffer for the next
623 read if that would leave enough lines, or else malloc a new one.
624 Some compaction mechanism is possible but probably not
626 last
= last
->next
= tmp
;
627 if (total_lines
- first
->nlines
> n_lines
)
630 total_lines
-= first
->nlines
;
634 tmp
= xmalloc (sizeof (LBUFFER
));
640 if (n_read
== SAFE_READ_ERROR
)
642 error (0, errno
, _("error reading %s"), quote (pretty_filename
));
647 /* If the file is empty, then bail out. */
648 if (last
->nbytes
== 0)
651 /* This prevents a core dump when the pipe contains no newlines. */
655 /* Count the incomplete line on files that don't end with a newline. */
656 if (last
->buffer
[last
->nbytes
- 1] != '\n')
662 /* Run through the list, printing lines. First, skip over unneeded
664 for (tmp
= first
; total_lines
- tmp
->nlines
> n_lines
; tmp
= tmp
->next
)
665 total_lines
-= tmp
->nlines
;
667 /* Find the correct beginning, then print the rest of the file. */
669 char const *beg
= tmp
->buffer
;
670 char const *buffer_end
= tmp
->buffer
+ tmp
->nbytes
;
671 if (total_lines
> n_lines
)
673 /* Skip `total_lines' - `n_lines' newlines. We made sure that
674 `total_lines' - `n_lines' <= `tmp->nlines'. */
676 for (j
= total_lines
- n_lines
; j
; --j
)
678 beg
= memchr (beg
, '\n', buffer_end
- beg
);
684 xwrite_stdout (beg
, buffer_end
- beg
);
687 for (tmp
= tmp
->next
; tmp
; tmp
= tmp
->next
)
688 xwrite_stdout (tmp
->buffer
, tmp
->nbytes
);
700 /* Print the last N_BYTES characters from the end of pipe FD.
701 This is a stripped down version of pipe_lines.
702 Return true if successful. */
705 pipe_bytes (const char *pretty_filename
, int fd
, uintmax_t n_bytes
,
712 struct charbuffer
*next
;
714 typedef struct charbuffer CBUFFER
;
715 CBUFFER
*first
, *last
, *tmp
;
716 size_t i
; /* Index into buffers. */
717 size_t total_bytes
= 0; /* Total characters in all buffers. */
721 first
= last
= xmalloc (sizeof (CBUFFER
));
724 tmp
= xmalloc (sizeof (CBUFFER
));
726 /* Input is always read into a fresh buffer. */
729 n_read
= safe_read (fd
, tmp
->buffer
, BUFSIZ
);
730 if (n_read
== 0 || n_read
== SAFE_READ_ERROR
)
733 tmp
->nbytes
= n_read
;
736 total_bytes
+= tmp
->nbytes
;
737 /* If there is enough room in the last buffer read, just append the new
738 one to it. This is because when reading from a pipe, `nbytes' can
739 often be very small. */
740 if (tmp
->nbytes
+ last
->nbytes
< BUFSIZ
)
742 memcpy (&last
->buffer
[last
->nbytes
], tmp
->buffer
, tmp
->nbytes
);
743 last
->nbytes
+= tmp
->nbytes
;
747 /* If there's not enough room, link the new buffer onto the end of
748 the list, then either free up the oldest buffer for the next
749 read if that would leave enough characters, or else malloc a new
750 one. Some compaction mechanism is possible but probably not
752 last
= last
->next
= tmp
;
753 if (total_bytes
- first
->nbytes
> n_bytes
)
756 total_bytes
-= first
->nbytes
;
761 tmp
= xmalloc (sizeof (CBUFFER
));
768 if (n_read
== SAFE_READ_ERROR
)
770 error (0, errno
, _("error reading %s"), quote (pretty_filename
));
775 /* Run through the list, printing characters. First, skip over unneeded
777 for (tmp
= first
; total_bytes
- tmp
->nbytes
> n_bytes
; tmp
= tmp
->next
)
778 total_bytes
-= tmp
->nbytes
;
780 /* Find the correct beginning, then print the rest of the file.
781 We made sure that `total_bytes' - `n_bytes' <= `tmp->nbytes'. */
782 if (total_bytes
> n_bytes
)
783 i
= total_bytes
- n_bytes
;
786 xwrite_stdout (&tmp
->buffer
[i
], tmp
->nbytes
- i
);
788 for (tmp
= tmp
->next
; tmp
; tmp
= tmp
->next
)
789 xwrite_stdout (tmp
->buffer
, tmp
->nbytes
);
801 /* Skip N_BYTES characters from the start of pipe FD, and print
802 any extra characters that were read beyond that.
803 Return 1 on error, 0 if ok, -1 if EOF. */
806 start_bytes (const char *pretty_filename
, int fd
, uintmax_t n_bytes
,
813 size_t bytes_read
= safe_read (fd
, buffer
, BUFSIZ
);
816 if (bytes_read
== SAFE_READ_ERROR
)
818 error (0, errno
, _("error reading %s"), quote (pretty_filename
));
821 *read_pos
+= bytes_read
;
822 if (bytes_read
<= n_bytes
)
823 n_bytes
-= bytes_read
;
826 size_t n_remaining
= bytes_read
- n_bytes
;
828 xwrite_stdout (&buffer
[n_bytes
], n_remaining
);
836 /* Skip N_LINES lines at the start of file or pipe FD, and print
837 any extra characters that were read beyond that.
838 Return 1 on error, 0 if ok, -1 if EOF. */
841 start_lines (const char *pretty_filename
, int fd
, uintmax_t n_lines
,
851 size_t bytes_read
= safe_read (fd
, buffer
, BUFSIZ
);
852 char *buffer_end
= buffer
+ bytes_read
;
853 if (bytes_read
== 0) /* EOF */
855 if (bytes_read
== SAFE_READ_ERROR
) /* error */
857 error (0, errno
, _("error reading %s"), quote (pretty_filename
));
861 *read_pos
+= bytes_read
;
863 while ((p
= memchr (p
, '\n', buffer_end
- p
)))
869 xwrite_stdout (p
, buffer_end
- p
);
877 /* Without inotify support, always return false. Otherwise, return false
878 when FD is open on a file known to reside on a local file system.
879 If fstatfs fails, give a diagnostic and return true.
880 If fstatfs cannot be called, return true. */
882 fremote (int fd
, const char *name
)
884 bool remote
= true; /* be conservative (poll by default). */
886 # if HAVE_FSTATFS && HAVE_STRUCT_STATFS_F_TYPE && defined __linux__
888 int err
= fstatfs (fd
, &buf
);
891 /* On at least linux-2.6.38, fstatfs fails with ENOSYS when FD
892 is open on a pipe. Treat that like a remote file. */
894 error (0, errno
, _("cannot determine location of %s. "
895 "reverting to polling"), quote (name
));
904 case S_MAGIC_FUSEBLK
:
905 case S_MAGIC_FUSECTL
:
924 /* Without inotify support, whether a file is remote is irrelevant.
925 Always return "false" in that case. */
926 # define fremote(fd, name) false
929 /* FIXME: describe */
932 recheck (struct File_spec
*f
, bool blocking
)
934 /* open/fstat the file and announce if dev/ino have changed */
935 struct stat new_stats
;
937 bool is_stdin
= (STREQ (f
->name
, "-"));
938 bool was_tailable
= f
->tailable
;
939 int prev_errnum
= f
->errnum
;
943 : open (f
->name
, O_RDONLY
| (blocking
? 0 : O_NONBLOCK
)));
945 assert (valid_file_spec (f
));
947 /* If the open fails because the file doesn't exist,
948 then mark the file as not tailable. */
949 f
->tailable
= !(reopen_inaccessible_files
&& fd
== -1);
951 if (fd
== -1 || fstat (fd
, &new_stats
) < 0)
959 /* FIXME-maybe: detect the case in which the file first becomes
960 unreadable (perms), and later becomes readable again and can
961 be seen to be the same file (dev/ino). Otherwise, tail prints
962 the entire contents of the file when it becomes readable. */
963 error (0, f
->errnum
, _("%s has become inaccessible"),
964 quote (pretty_name (f
)));
968 /* say nothing... it's still not tailable */
971 else if (prev_errnum
!= errno
)
973 error (0, errno
, "%s", pretty_name (f
));
976 else if (!IS_TAILABLE_FILE_TYPE (new_stats
.st_mode
))
980 error (0, 0, _("%s has been replaced with an untailable file;\
981 giving up on this name"),
982 quote (pretty_name (f
)));
985 else if (!disable_inotify
&& fremote (fd
, pretty_name (f
)))
989 error (0, 0, _("%s has been replaced with a remote file. "
990 "giving up on this name"), quote (pretty_name (f
)));
1002 close_fd (fd
, pretty_name (f
));
1003 close_fd (f
->fd
, pretty_name (f
));
1006 else if (prev_errnum
&& prev_errnum
!= ENOENT
)
1009 assert (f
->fd
== -1);
1010 error (0, 0, _("%s has become accessible"), quote (pretty_name (f
)));
1012 else if (f
->ino
!= new_stats
.st_ino
|| f
->dev
!= new_stats
.st_dev
)
1018 _("%s has appeared; following end of new file"),
1019 quote (pretty_name (f
)));
1023 /* Close the old one. */
1024 close_fd (f
->fd
, pretty_name (f
));
1026 /* File has been replaced (e.g., via log rotation) --
1027 tail the new one. */
1029 _("%s has been replaced; following end of new file"),
1030 quote (pretty_name (f
)));
1037 /* This happens when one iteration finds the file missing,
1038 then the preceding <dev,inode> pair is reused as the
1039 file is recreated. */
1044 close_fd (fd
, pretty_name (f
));
1050 /* Start at the beginning of the file. */
1051 record_open_fd (f
, fd
, 0, &new_stats
, (is_stdin
? -1 : blocking
));
1052 xlseek (fd
, 0, SEEK_SET
, pretty_name (f
));
1056 /* Return true if any of the N_FILES files in F are live, i.e., have
1057 open file descriptors. */
1060 any_live_files (const struct File_spec
*f
, size_t n_files
)
1064 for (i
= 0; i
< n_files
; i
++)
1070 /* Tail N_FILES files forever, or until killed.
1071 The pertinent information for each file is stored in an entry of F.
1072 Loop over each of them, doing an fstat to see if they have changed size,
1073 and an occasional open/fstat to see if any dev/ino pair has changed.
1074 If none of them have changed size in one iteration, sleep for a
1075 while and try again. Continue until the user interrupts us. */
1078 tail_forever (struct File_spec
*f
, size_t n_files
, double sleep_interval
)
1080 /* Use blocking I/O as an optimization, when it's easy. */
1081 bool blocking
= (pid
== 0 && follow_mode
== Follow_descriptor
1082 && n_files
== 1 && ! S_ISREG (f
[0].mode
));
1084 bool writer_is_dead
= false;
1091 bool any_input
= false;
1093 for (i
= 0; i
< n_files
; i
++)
1099 uintmax_t bytes_read
;
1106 recheck (&f
[i
], blocking
);
1111 name
= pretty_name (&f
[i
]);
1114 if (f
[i
].blocking
!= blocking
)
1116 int old_flags
= fcntl (fd
, F_GETFL
);
1117 int new_flags
= old_flags
| (blocking
? 0 : O_NONBLOCK
);
1119 || (new_flags
!= old_flags
1120 && fcntl (fd
, F_SETFL
, new_flags
) == -1))
1122 /* Don't update f[i].blocking if fcntl fails. */
1123 if (S_ISREG (f
[i
].mode
) && errno
== EPERM
)
1125 /* This happens when using tail -f on a file with
1126 the append-only attribute. */
1129 error (EXIT_FAILURE
, errno
,
1130 _("%s: cannot change nonblocking mode"), name
);
1133 f
[i
].blocking
= blocking
;
1138 if (fstat (fd
, &stats
) != 0)
1141 f
[i
].errnum
= errno
;
1142 error (0, errno
, "%s", name
);
1146 if (f
[i
].mode
== stats
.st_mode
1147 && (! S_ISREG (stats
.st_mode
) || f
[i
].size
== stats
.st_size
)
1148 && timespec_cmp (f
[i
].mtime
, get_stat_mtime (&stats
)) == 0)
1150 if ((max_n_unchanged_stats_between_opens
1151 <= f
[i
].n_unchanged_stats
++)
1152 && follow_mode
== Follow_name
)
1154 recheck (&f
[i
], f
[i
].blocking
);
1155 f
[i
].n_unchanged_stats
= 0;
1160 /* This file has changed. Print out what we can, and
1161 then keep looping. */
1163 f
[i
].mtime
= get_stat_mtime (&stats
);
1164 f
[i
].mode
= stats
.st_mode
;
1167 f
[i
].n_unchanged_stats
= 0;
1169 if (S_ISREG (mode
) && stats
.st_size
< f
[i
].size
)
1171 error (0, 0, _("%s: file truncated"), name
);
1173 xlseek (fd
, stats
.st_size
, SEEK_SET
, name
);
1174 f
[i
].size
= stats
.st_size
;
1181 write_header (name
);
1186 bytes_read
= dump_remainder (name
, fd
,
1188 ? COPY_A_BUFFER
: COPY_TO_EOF
));
1189 any_input
|= (bytes_read
!= 0);
1190 f
[i
].size
+= bytes_read
;
1193 if (! any_live_files (f
, n_files
) && ! reopen_inaccessible_files
)
1195 error (0, 0, _("no files remaining"));
1199 if ((!any_input
|| blocking
) && fflush (stdout
) != 0)
1200 error (EXIT_FAILURE
, errno
, _("write error"));
1202 /* If nothing was read, sleep and/or check for dead writers. */
1208 /* Once the writer is dead, read the files once more to
1209 avoid a race condition. */
1210 writer_is_dead
= (pid
!= 0
1211 && kill (pid
, 0) != 0
1212 /* Handle the case in which you cannot send a
1213 signal to the writer, so kill fails and sets
1217 if (!writer_is_dead
&& xnanosleep (sleep_interval
))
1218 error (EXIT_FAILURE
, errno
, _("cannot read realtime clock"));
1226 /* Return true if any of the N_FILES files in F is remote, i.e., has
1227 an open file descriptor and is on a network file system. */
1230 any_remote_file (const struct File_spec
*f
, size_t n_files
)
1234 for (i
= 0; i
< n_files
; i
++)
1235 if (0 <= f
[i
].fd
&& f
[i
].remote
)
1240 /* Return true if any of the N_FILES files in F represents
1241 stdin and is tailable. */
1244 tailable_stdin (const struct File_spec
*f
, size_t n_files
)
1248 for (i
= 0; i
< n_files
; i
++)
1249 if (!f
[i
].ignore
&& STREQ (f
[i
].name
, "-"))
1255 wd_hasher (const void *entry
, size_t tabsize
)
1257 const struct File_spec
*spec
= entry
;
1258 return spec
->wd
% tabsize
;
1262 wd_comparator (const void *e1
, const void *e2
)
1264 const struct File_spec
*spec1
= e1
;
1265 const struct File_spec
*spec2
= e2
;
1266 return spec1
->wd
== spec2
->wd
;
1269 /* Helper function used by `tail_forever_inotify'. */
1271 check_fspec (struct File_spec
*fspec
, int wd
, int *prev_wd
)
1274 char const *name
= pretty_name (fspec
);
1276 if (fstat (fspec
->fd
, &stats
) != 0)
1278 close_fd (fspec
->fd
, name
);
1280 fspec
->errnum
= errno
;
1284 if (S_ISREG (fspec
->mode
) && stats
.st_size
< fspec
->size
)
1286 error (0, 0, _("%s: file truncated"), name
);
1288 xlseek (fspec
->fd
, stats
.st_size
, SEEK_SET
, name
);
1289 fspec
->size
= stats
.st_size
;
1291 else if (S_ISREG (fspec
->mode
) && stats
.st_size
== fspec
->size
1292 && timespec_cmp (fspec
->mtime
, get_stat_mtime (&stats
)) == 0)
1298 write_header (name
);
1302 uintmax_t bytes_read
= dump_remainder (name
, fspec
->fd
, COPY_TO_EOF
);
1303 fspec
->size
+= bytes_read
;
1305 if (fflush (stdout
) != 0)
1306 error (EXIT_FAILURE
, errno
, _("write error"));
1309 /* Attempt to tail N_FILES files forever, or until killed.
1310 Check modifications using the inotify events system.
1311 Return false on error, or true to revert to polling. */
1313 tail_forever_inotify (int wd
, struct File_spec
*f
, size_t n_files
,
1314 double sleep_interval
)
1316 unsigned int max_realloc
= 3;
1318 /* Map an inotify watch descriptor to the name of the file it's watching. */
1319 Hash_table
*wd_to_name
;
1321 bool found_watchable_file
= false;
1322 bool found_unwatchable_dir
= false;
1323 bool no_inotify_resources
= false;
1324 bool writer_is_dead
= false;
1328 size_t evbuf_off
= 0;
1331 wd_to_name
= hash_initialize (n_files
, NULL
, wd_hasher
, wd_comparator
, NULL
);
1335 /* Add an inotify watch for each watched file. If -F is specified then watch
1336 its parent directory too, in this way when they re-appear we can add them
1337 again to the watch list. */
1339 for (i
= 0; i
< n_files
; i
++)
1343 size_t fnlen
= strlen (f
[i
].name
);
1349 if (follow_mode
== Follow_name
)
1351 size_t dirlen
= dir_len (f
[i
].name
);
1352 char prev
= f
[i
].name
[dirlen
];
1353 f
[i
].basename_start
= last_component (f
[i
].name
) - f
[i
].name
;
1355 f
[i
].name
[dirlen
] = '\0';
1357 /* It's fine to add the same directory more than once.
1358 In that case the same watch descriptor is returned. */
1359 f
[i
].parent_wd
= inotify_add_watch (wd
, dirlen
? f
[i
].name
: ".",
1360 (IN_CREATE
| IN_MOVED_TO
1363 f
[i
].name
[dirlen
] = prev
;
1365 if (f
[i
].parent_wd
< 0)
1367 if (errno
!= ENOSPC
) /* suppress confusing error. */
1368 error (0, errno
, _("cannot watch parent directory of %s"),
1371 error (0, 0, _("inotify resources exhausted"));
1372 found_unwatchable_dir
= true;
1373 /* We revert to polling below. Note invalid uses
1374 of the inotify API will still be diagnosed. */
1379 f
[i
].wd
= inotify_add_watch (wd
, f
[i
].name
, inotify_wd_mask
);
1383 if (errno
== ENOSPC
)
1385 no_inotify_resources
= true;
1386 error (0, 0, _("inotify resources exhausted"));
1388 else if (errno
!= f
[i
].errnum
)
1389 error (0, errno
, _("cannot watch %s"), quote (f
[i
].name
));
1393 if (hash_insert (wd_to_name
, &(f
[i
])) == NULL
)
1396 found_watchable_file
= true;
1400 /* Linux kernel 2.6.24 at least has a bug where eventually, ENOSPC is always
1401 returned by inotify_add_watch. In any case we should revert to polling
1402 when there are no inotify resources. Also a specified directory may not
1403 be currently present or accessible, so revert to polling. */
1404 if (no_inotify_resources
|| found_unwatchable_dir
)
1406 /* FIXME: release hash and inotify resources allocated above. */
1410 if (follow_mode
== Follow_descriptor
&& !found_watchable_file
)
1413 prev_wd
= f
[n_files
- 1].wd
;
1415 /* Check files again. New data can be available since last time we checked
1416 and before they are watched by inotify. */
1417 for (i
= 0; i
< n_files
; i
++)
1420 check_fspec (&f
[i
], f
[i
].wd
, &prev_wd
);
1423 evlen
+= sizeof (struct inotify_event
) + 1;
1424 evbuf
= xmalloc (evlen
);
1426 /* Wait for inotify events and handle them. Events on directories
1427 ensure that watched files can be re-added when following by name.
1428 This loop blocks on the `safe_read' call until a new event is notified.
1429 But when --pid=P is specified, tail usually waits via the select. */
1432 struct File_spec
*fspec
;
1433 struct inotify_event
*ev
;
1435 /* When following by name without --retry, and the last file has
1436 been unlinked or renamed-away, diagnose it and return. */
1437 if (follow_mode
== Follow_name
1438 && ! reopen_inaccessible_files
1439 && hash_get_n_entries (wd_to_name
) == 0)
1441 error (0, 0, _("no files remaining"));
1445 /* When watching a PID, ensure that a read from WD will not block
1450 exit (EXIT_SUCCESS
);
1452 writer_is_dead
= (kill (pid
, 0) != 0 && errno
!= EPERM
);
1454 struct timeval delay
; /* how long to wait for file changes. */
1456 delay
.tv_sec
= delay
.tv_usec
= 0;
1459 delay
.tv_sec
= (time_t) sleep_interval
;
1460 delay
.tv_usec
= 1000000 * (sleep_interval
- delay
.tv_sec
);
1467 int file_change
= select (wd
+ 1, &rfd
, NULL
, NULL
, &delay
);
1469 if (file_change
== 0)
1471 else if (file_change
== -1)
1472 error (EXIT_FAILURE
, errno
, _("error monitoring inotify event"));
1475 if (len
<= evbuf_off
)
1477 len
= safe_read (wd
, evbuf
, evlen
);
1480 /* For kernels prior to 2.6.21, read returns 0 when the buffer
1482 if ((len
== 0 || (len
== SAFE_READ_ERROR
&& errno
== EINVAL
))
1487 evbuf
= xrealloc (evbuf
, evlen
);
1491 if (len
== 0 || len
== SAFE_READ_ERROR
)
1492 error (EXIT_FAILURE
, errno
, _("error reading inotify event"));
1495 ev
= (struct inotify_event
*) (evbuf
+ evbuf_off
);
1496 evbuf_off
+= sizeof (*ev
) + ev
->len
;
1498 if (ev
->len
) /* event on ev->name in watched directory */
1501 for (j
= 0; j
< n_files
; j
++)
1503 /* With N=hundreds of frequently-changing files, this O(N^2)
1504 process might be a problem. FIXME: use a hash table? */
1505 if (f
[j
].parent_wd
== ev
->wd
1506 && STREQ (ev
->name
, f
[j
].name
+ f
[j
].basename_start
))
1510 /* It is not a watched file. */
1514 /* It's fine to add the same file more than once. */
1515 int new_wd
= inotify_add_watch (wd
, f
[j
].name
, inotify_wd_mask
);
1518 error (0, errno
, _("cannot watch %s"), quote (f
[j
].name
));
1524 /* Remove `fspec' and re-add it using `new_fd' as its key. */
1525 hash_delete (wd_to_name
, fspec
);
1528 /* If the file was moved then inotify will use the source file wd for
1529 the destination file. Make sure the key is not present in the
1531 struct File_spec
*prev
= hash_delete (wd_to_name
, fspec
);
1532 if (prev
&& prev
!= fspec
)
1534 if (follow_mode
== Follow_name
)
1535 recheck (prev
, false);
1537 close_fd (prev
->fd
, pretty_name (prev
));
1540 if (hash_insert (wd_to_name
, fspec
) == NULL
)
1543 if (follow_mode
== Follow_name
)
1544 recheck (fspec
, false);
1548 struct File_spec key
;
1550 fspec
= hash_lookup (wd_to_name
, &key
);
1556 if (ev
->mask
& (IN_ATTRIB
| IN_DELETE_SELF
| IN_MOVE_SELF
))
1558 /* For IN_DELETE_SELF, we always want to remove the watch.
1559 However, for IN_MOVE_SELF (the file we're watching has
1560 been clobbered via a rename), when tailing by NAME, we
1561 must continue to watch the file. It's only when following
1562 by file descriptor that we must remove the watch. */
1563 if ((ev
->mask
& IN_DELETE_SELF
)
1564 || ((ev
->mask
& IN_MOVE_SELF
)
1565 && follow_mode
== Follow_descriptor
))
1567 inotify_rm_watch (wd
, fspec
->wd
);
1568 hash_delete (wd_to_name
, fspec
);
1570 if (follow_mode
== Follow_name
)
1571 recheck (fspec
, false);
1575 check_fspec (fspec
, ev
->wd
, &prev_wd
);
1580 /* Output the last N_BYTES bytes of file FILENAME open for reading in FD.
1581 Return true if successful. */
1584 tail_bytes (const char *pretty_filename
, int fd
, uintmax_t n_bytes
,
1585 uintmax_t *read_pos
)
1589 if (fstat (fd
, &stats
))
1591 error (0, errno
, _("cannot fstat %s"), quote (pretty_filename
));
1597 if ( ! presume_input_pipe
1598 && S_ISREG (stats
.st_mode
) && n_bytes
<= OFF_T_MAX
)
1600 xlseek (fd
, n_bytes
, SEEK_CUR
, pretty_filename
);
1601 *read_pos
+= n_bytes
;
1605 int t
= start_bytes (pretty_filename
, fd
, n_bytes
, read_pos
);
1609 *read_pos
+= dump_remainder (pretty_filename
, fd
, COPY_TO_EOF
);
1613 if ( ! presume_input_pipe
1614 && S_ISREG (stats
.st_mode
) && n_bytes
<= OFF_T_MAX
)
1616 off_t current_pos
= xlseek (fd
, 0, SEEK_CUR
, pretty_filename
);
1617 off_t end_pos
= xlseek (fd
, 0, SEEK_END
, pretty_filename
);
1618 off_t diff
= end_pos
- current_pos
;
1619 /* Be careful here. The current position may actually be
1620 beyond the end of the file. */
1621 off_t bytes_remaining
= diff
< 0 ? 0 : diff
;
1624 if (bytes_remaining
<= nb
)
1626 /* From the current position to end of file, there are no
1627 more bytes than have been requested. So reposition the
1628 file pointer to the incoming current position and print
1629 everything after that. */
1630 *read_pos
= xlseek (fd
, current_pos
, SEEK_SET
, pretty_filename
);
1634 /* There are more bytes remaining than were requested.
1636 *read_pos
= xlseek (fd
, -nb
, SEEK_END
, pretty_filename
);
1638 *read_pos
+= dump_remainder (pretty_filename
, fd
, n_bytes
);
1641 return pipe_bytes (pretty_filename
, fd
, n_bytes
, read_pos
);
1646 /* Output the last N_LINES lines of file FILENAME open for reading in FD.
1647 Return true if successful. */
1650 tail_lines (const char *pretty_filename
, int fd
, uintmax_t n_lines
,
1651 uintmax_t *read_pos
)
1655 if (fstat (fd
, &stats
))
1657 error (0, errno
, _("cannot fstat %s"), quote (pretty_filename
));
1663 int t
= start_lines (pretty_filename
, fd
, n_lines
, read_pos
);
1666 *read_pos
+= dump_remainder (pretty_filename
, fd
, COPY_TO_EOF
);
1670 off_t start_pos
= -1;
1673 /* Use file_lines only if FD refers to a regular file for
1674 which lseek (... SEEK_END) works. */
1675 if ( ! presume_input_pipe
1676 && S_ISREG (stats
.st_mode
)
1677 && (start_pos
= lseek (fd
, 0, SEEK_CUR
)) != -1
1678 && start_pos
< (end_pos
= lseek (fd
, 0, SEEK_END
)))
1680 *read_pos
= end_pos
;
1682 && ! file_lines (pretty_filename
, fd
, n_lines
,
1683 start_pos
, end_pos
, read_pos
))
1688 /* Under very unlikely circumstances, it is possible to reach
1689 this point after positioning the file pointer to end of file
1690 via the `lseek (...SEEK_END)' above. In that case, reposition
1691 the file pointer back to start_pos before calling pipe_lines. */
1692 if (start_pos
!= -1)
1693 xlseek (fd
, start_pos
, SEEK_SET
, pretty_filename
);
1695 return pipe_lines (pretty_filename
, fd
, n_lines
, read_pos
);
1701 /* Display the last N_UNITS units of file FILENAME, open for reading
1702 via FD. Set *READ_POS to the position of the input stream pointer.
1703 *READ_POS is usually the number of bytes read and corresponds to an
1704 offset from the beginning of a file. However, it may be larger than
1705 OFF_T_MAX (as for an input pipe), and may also be larger than the
1706 number of bytes read (when an input pointer is initially not at
1707 beginning of file), and may be far greater than the number of bytes
1708 actually read for an input file that is seekable.
1709 Return true if successful. */
1712 tail (const char *filename
, int fd
, uintmax_t n_units
,
1713 uintmax_t *read_pos
)
1717 return tail_lines (filename
, fd
, n_units
, read_pos
);
1719 return tail_bytes (filename
, fd
, n_units
, read_pos
);
1722 /* Display the last N_UNITS units of the file described by F.
1723 Return true if successful. */
1726 tail_file (struct File_spec
*f
, uintmax_t n_units
)
1731 bool is_stdin
= (STREQ (f
->name
, "-"));
1735 have_read_stdin
= true;
1737 if (O_BINARY
&& ! isatty (STDIN_FILENO
))
1738 xfreopen (NULL
, "rb", stdin
);
1741 fd
= open (f
->name
, O_RDONLY
| O_BINARY
);
1743 f
->tailable
= !(reopen_inaccessible_files
&& fd
== -1);
1755 error (0, errno
, _("cannot open %s for reading"),
1756 quote (pretty_name (f
)));
1764 write_header (pretty_name (f
));
1765 ok
= tail (pretty_name (f
), fd
, n_units
, &read_pos
);
1770 #if TEST_RACE_BETWEEN_FINAL_READ_AND_INITIAL_FSTAT
1771 /* Before the tail function provided `read_pos', there was
1772 a race condition described in the URL below. This sleep
1773 call made the window big enough to exercise the problem. */
1777 if (fstat (fd
, &stats
) < 0)
1781 error (0, errno
, _("error reading %s"), quote (pretty_name (f
)));
1783 else if (!IS_TAILABLE_FILE_TYPE (stats
.st_mode
))
1785 error (0, 0, _("%s: cannot follow end of this type of file;\
1786 giving up on this name"),
1795 close_fd (fd
, pretty_name (f
));
1800 /* Note: we must use read_pos here, not stats.st_size,
1801 to avoid a race condition described by Ken Raeburn:
1802 http://mail.gnu.org/archive/html/bug-textutils/2003-05/msg00007.html */
1803 record_open_fd (f
, fd
, read_pos
, &stats
, (is_stdin
? -1 : 1));
1804 f
->remote
= fremote (fd
, pretty_name (f
));
1809 if (!is_stdin
&& close (fd
))
1811 error (0, errno
, _("error reading %s"), quote (pretty_name (f
)));
1820 /* If obsolete usage is allowed, and the command line arguments are of
1821 the obsolete form and the option string is well-formed, set
1822 *N_UNITS, the globals COUNT_LINES, FOREVER, and FROM_START, and
1823 return true. If the command line arguments are obviously incorrect
1824 (e.g., because obsolete usage is not allowed and the arguments are
1825 incorrect for non-obsolete usage), report an error and exit.
1826 Otherwise, return false and don't modify any parameter or global
1830 parse_obsolete_option (int argc
, char * const *argv
, uintmax_t *n_units
)
1833 const char *n_string
;
1834 const char *n_string_end
;
1835 bool obsolete_usage
;
1836 int default_count
= DEFAULT_N_LINES
;
1838 bool t_count_lines
= true;
1839 bool t_forever
= false;
1841 /* With the obsolete form, there is one option string and at most
1842 one file argument. Watch out for "-" and "--", though. */
1844 || (argc
== 3 && ! (argv
[2][0] == '-' && argv
[2][1]))
1845 || (3 <= argc
&& argc
<= 4 && STREQ (argv
[2], "--"))))
1848 obsolete_usage
= (posix2_version () < 200112);
1857 /* Leading "+" is a file name in the non-obsolete form. */
1858 if (!obsolete_usage
)
1861 t_from_start
= true;
1865 /* In the non-obsolete form, "-" is standard input and "-c"
1866 requires an option-argument. The obsolete multidigit options
1867 are supported as a GNU extension even when conforming to
1868 POSIX 1003.1-2001, so don't complain about them. */
1869 if (!obsolete_usage
&& !p
[p
[0] == 'c'])
1872 t_from_start
= false;
1877 while (ISDIGIT (*p
))
1883 case 'b': default_count
*= 512; /* Fall through. */
1884 case 'c': t_count_lines
= false; /* Fall through. */
1885 case 'l': p
++; break;
1897 if (n_string
== n_string_end
)
1898 *n_units
= default_count
;
1899 else if ((xstrtoumax (n_string
, NULL
, 10, n_units
, "b")
1900 & ~LONGINT_INVALID_SUFFIX_CHAR
)
1902 error (EXIT_FAILURE
, 0, _("number in %s is too large"), quote (argv
[1]));
1905 from_start
= t_from_start
;
1906 count_lines
= t_count_lines
;
1907 forever
= t_forever
;
1913 parse_options (int argc
, char **argv
,
1914 uintmax_t *n_units
, enum header_mode
*header_mode
,
1915 double *sleep_interval
)
1919 while ((c
= getopt_long (argc
, argv
, "c:n:fFqs:v0123456789",
1920 long_options
, NULL
))
1927 follow_mode
= Follow_name
;
1928 reopen_inaccessible_files
= true;
1933 count_lines
= (c
== 'n');
1936 else if (*optarg
== '-')
1941 s_err
= xstrtoumax (optarg
, NULL
, 10, n_units
, "bkKmMGTPEZY0");
1942 if (s_err
!= LONGINT_OK
)
1944 error (EXIT_FAILURE
, 0, "%s: %s", optarg
,
1946 ? _("invalid number of lines")
1947 : _("invalid number of bytes")));
1953 case LONG_FOLLOW_OPTION
:
1956 follow_mode
= DEFAULT_FOLLOW_MODE
;
1958 follow_mode
= XARGMATCH ("--follow", optarg
,
1959 follow_mode_string
, follow_mode_map
);
1963 reopen_inaccessible_files
= true;
1966 case MAX_UNCHANGED_STATS_OPTION
:
1967 /* --max-unchanged-stats=N */
1968 if (xstrtoumax (optarg
, NULL
, 10,
1969 &max_n_unchanged_stats_between_opens
,
1973 error (EXIT_FAILURE
, 0,
1974 _("%s: invalid maximum number of unchanged stats between opens"),
1979 case DISABLE_INOTIFY_OPTION
:
1980 disable_inotify
= true;
1986 unsigned long int tmp_ulong
;
1987 s_err
= xstrtoul (optarg
, NULL
, 10, &tmp_ulong
, "");
1988 if (s_err
!= LONGINT_OK
|| tmp_ulong
> PID_T_MAX
)
1990 error (EXIT_FAILURE
, 0, _("%s: invalid PID"), optarg
);
1996 case PRESUME_INPUT_PIPE_OPTION
:
1997 presume_input_pipe
= true;
2001 *header_mode
= never
;
2007 if (! (xstrtod (optarg
, NULL
, &s
, c_strtod
) && 0 <= s
))
2008 error (EXIT_FAILURE
, 0,
2009 _("%s: invalid number of seconds"), optarg
);
2010 *sleep_interval
= s
;
2015 *header_mode
= always
;
2018 case_GETOPT_HELP_CHAR
;
2020 case_GETOPT_VERSION_CHAR (PROGRAM_NAME
, AUTHORS
);
2022 case '0': case '1': case '2': case '3': case '4':
2023 case '5': case '6': case '7': case '8': case '9':
2024 error (EXIT_FAILURE
, 0,
2025 _("option used in invalid context -- %c"), c
);
2028 usage (EXIT_FAILURE
);
2032 if (reopen_inaccessible_files
&& follow_mode
!= Follow_name
)
2033 error (0, 0, _("warning: --retry is useful mainly when following by name"));
2035 if (pid
&& !forever
)
2037 _("warning: PID ignored; --pid=PID is useful only when following"));
2038 else if (pid
&& kill (pid
, 0) != 0 && errno
== ENOSYS
)
2040 error (0, 0, _("warning: --pid=PID is not supported on this system"));
2045 /* Mark as '.ignore'd each member of F that corresponds to a
2046 pipe or fifo, and return the number of non-ignored members. */
2048 ignore_fifo_and_pipe (struct File_spec
*f
, size_t n_files
)
2050 /* When there is no FILE operand and stdin is a pipe or FIFO
2051 POSIX requires that tail ignore the -f option.
2052 Since we allow multiple FILE operands, we extend that to say: with -f,
2053 ignore any "-" operand that corresponds to a pipe or FIFO. */
2054 size_t n_viable
= 0;
2057 for (i
= 0; i
< n_files
; i
++)
2059 bool is_a_fifo_or_pipe
=
2060 (STREQ (f
[i
].name
, "-")
2063 && (S_ISFIFO (f
[i
].mode
)
2064 || (HAVE_FIFO_PIPES
!= 1 && isapipe (f
[i
].fd
))));
2065 if (is_a_fifo_or_pipe
)
2075 main (int argc
, char **argv
)
2077 enum header_mode header_mode
= multiple_files
;
2079 /* If from_start, the number of items to skip before printing; otherwise,
2080 the number of items at the end of the file to print. Although the type
2081 is signed, the value is never negative. */
2082 uintmax_t n_units
= DEFAULT_N_LINES
;
2085 struct File_spec
*F
;
2087 bool obsolete_option
;
2089 /* The number of seconds to sleep between iterations.
2090 During one iteration, every file name or descriptor is checked to
2091 see if it has changed. */
2092 double sleep_interval
= 1.0;
2094 initialize_main (&argc
, &argv
);
2095 set_program_name (argv
[0]);
2096 setlocale (LC_ALL
, "");
2097 bindtextdomain (PACKAGE
, LOCALEDIR
);
2098 textdomain (PACKAGE
);
2100 atexit (close_stdout
);
2102 have_read_stdin
= false;
2105 forever
= from_start
= print_headers
= false;
2106 obsolete_option
= parse_obsolete_option (argc
, argv
, &n_units
);
2107 argc
-= obsolete_option
;
2108 argv
+= obsolete_option
;
2109 parse_options (argc
, argv
, &n_units
, &header_mode
, &sleep_interval
);
2111 /* To start printing with item N_UNITS from the start of the file, skip
2112 N_UNITS - 1 items. `tail -n +0' is actually meaningless, but for Unix
2113 compatibility it's treated the same as `tail -n +1'. */
2122 n_files
= argc
- optind
;
2123 file
= argv
+ optind
;
2127 static char *dummy_stdin
= (char *) "-";
2129 file
= &dummy_stdin
;
2133 bool found_hyphen
= false;
2135 for (i
= 0; i
< n_files
; i
++)
2136 if (STREQ (file
[i
], "-"))
2137 found_hyphen
= true;
2139 /* When following by name, there must be a name. */
2140 if (found_hyphen
&& follow_mode
== Follow_name
)
2141 error (EXIT_FAILURE
, 0, _("cannot follow %s by name"), quote ("-"));
2143 /* When following forever, warn if any file is `-'.
2144 This is only a warning, since tail's output (before a failing seek,
2145 and that from any non-stdin files) might still be useful. */
2146 if (forever
&& found_hyphen
&& isatty (STDIN_FILENO
))
2147 error (0, 0, _("warning: following standard input"
2148 " indefinitely is ineffective"));
2151 F
= xnmalloc (n_files
, sizeof *F
);
2152 for (i
= 0; i
< n_files
; i
++)
2153 F
[i
].name
= file
[i
];
2155 if (header_mode
== always
2156 || (header_mode
== multiple_files
&& n_files
> 1))
2157 print_headers
= true;
2159 if (O_BINARY
&& ! isatty (STDOUT_FILENO
))
2160 xfreopen (NULL
, "wb", stdout
);
2162 for (i
= 0; i
< n_files
; i
++)
2163 ok
&= tail_file (&F
[i
], n_units
);
2165 if (forever
&& ignore_fifo_and_pipe (F
, n_files
))
2168 /* tailable_stdin() checks if the user specifies stdin via "-",
2169 or implicitly by providing no arguments. If so, we won't use inotify.
2170 Technically, on systems with a working /dev/stdin, we *could*,
2171 but would it be worth it? Verifying that it's a real device
2172 and hooked up to stdin is not trivial, while reverting to
2173 non-inotify-based tail_forever is easy and portable.
2175 any_remote_file() checks if the user has specified any
2176 files that reside on remote file systems. inotify is not used
2177 in this case because it would miss any updates to the file
2178 that were not initiated from the local system.
2180 FIXME: inotify doesn't give any notification when a new
2181 (remote) file or directory is mounted on top a watched file.
2182 When follow_mode == Follow_name we would ideally like to detect that.
2183 Note if there is a change to the original file then we'll
2184 recheck it and follow the new file, or ignore it if the
2185 file has changed to being remote.
2187 FIXME: when using inotify, and a directory for a watched file
2188 is recreated, then we don't recheck any new file when
2189 follow_mode == Follow_name */
2190 if (!disable_inotify
&& (tailable_stdin (F
, n_files
)
2191 || any_remote_file (F
, n_files
)))
2192 disable_inotify
= true;
2194 if (!disable_inotify
)
2196 int wd
= inotify_init ();
2199 /* Flush any output from tail_file, now, since
2200 tail_forever_inotify flushes only after writing,
2201 not before reading. */
2202 if (fflush (stdout
) != 0)
2203 error (EXIT_FAILURE
, errno
, _("write error"));
2205 if (!tail_forever_inotify (wd
, F
, n_files
, sleep_interval
))
2206 exit (EXIT_FAILURE
);
2208 error (0, errno
, _("inotify cannot be used, reverting to polling"));
2211 disable_inotify
= true;
2212 tail_forever (F
, n_files
, sleep_interval
);
2215 if (have_read_stdin
&& close (STDIN_FILENO
) < 0)
2216 error (EXIT_FAILURE
, errno
, "-");
2217 exit (ok
? EXIT_SUCCESS
: EXIT_FAILURE
);