/* FIXME: describe */
unsigned int n_consecutive_size_changes;
- /* FIXME: describe */
- int missing;
+ /* A file is tailable if it is a regular file or a fifo and it is
+ readable. */
+ int tailable;
/* The value of errno seen last time we checked this file. */
int errnum;
};
/* FIXME: describe */
-static int allow_missing;
+static int reopen_inaccessible_files;
/* If nonzero, interpret the numeric argument as the number of lines.
Otherwise, interpret it as the number of bytes. */
};
/* When tailing a file by name, if there have been this many consecutive
- stat calls for which the size has remained the same, then open/fstat
+ iterations for which the size has remained the same, then open/fstat
the file to determine if that file name is still associated with the
same device/inode-number pair as before. This option is meaningful only
when following by name. --max-unchanged-stats=N */
After detecting this many consecutive size changes for a file, open/fstat
the file to determine if that file name is still associated with the
same device/inode-number pair as before. This option is meaningful only
- when following by name. --max-n-consecutive-size-changes=N */
+ when following by name. --max-consecutive-size-changes=N */
#define DEFAULT_MAX_N_CONSECUTIVE_SIZE_CHANGES 200
static unsigned long max_n_consecutive_size_changes_between_opens =
DEFAULT_MAX_N_CONSECUTIVE_SIZE_CHANGES;
/* The name this program was run with. */
char *program_name;
-/* The number of seconds to sleep between accesses. */
+/* The number of seconds to sleep between iterations.
+ During one iteration, every file name or descriptor is checked to
+ see if it has changed. */
+/* FIXME: allow fractional seconds */
static unsigned int sleep_interval = 1;
/* Nonzero if we have ever read standard input. */
static struct option const long_options[] =
{
+ /* --allow-missing is deprecated; use --retry instead
+ FIXME: remove it some day */
{"allow-missing", no_argument, NULL, CHAR_MAX + 1},
{"bytes", required_argument, NULL, 'c'},
{"follow", optional_argument, NULL, 'f'},
{"max-unchanged-stats", required_argument, NULL, CHAR_MAX + 2},
{"max-consecutive-size-changes", required_argument, NULL, CHAR_MAX + 3},
{"quiet", no_argument, NULL, 'q'},
+ {"retry", no_argument, NULL, CHAR_MAX + 1},
{"silent", no_argument, NULL, 'q'},
{"sleep-interval", required_argument, NULL, 's'},
{"verbose", no_argument, NULL, 'v'},
"),
program_name);
printf (_("\
-Print last 10 lines of each FILE to standard output.\n\
+Print the last %d lines of each FILE to standard output.\n\
With more than one FILE, precede each with a header giving the file name.\n\
With no FILE, or when FILE is -, read standard input.\n\
\n\
- --allow-missing FIXME\n\
+ --retry keep trying to open a file even if it is\n\
+ inaccessible when tail starts or if it becomes\n\
+ inaccessible later -- useful only with -f\n\
-c, --bytes=N output the last N bytes\n\
- -f, --follow[={name|descriptor}] output appended data as the file grows\n\
- -n, --lines=N output the last N lines, instead of last 10\n\
- --max-unchanged-stats=N FIXME describe and mention default\n\
- --max-consecutive-size-changes=N FIXME describe and mention default\n\
+ -f, --follow[={name|descriptor}] output appended data as the file grows;\n\
+ -f, --follow, and --follow=descriptor are\n\
+ equivalent\n\
+ -n, --lines=N output the last N lines, instead of the last %d\n\
+ --max-unchanged-stats=N see the texinfo documentation\n\
+ (the default is %d)\n\
+ --max-consecutive-size-changes=N see the texinfo documentation\n\
+ (the default is %d)\n\
-q, --quiet, --silent never output headers giving file names\n\
-s, --sleep-interval=S with -f, sleep S seconds between iterations\n\
-v, --verbose always output headers giving file names\n\
or +VALUE is treated like -n VALUE or -n +VALUE unless VALUE has one of\n\
the [bkm] suffix multipliers, in which case it is treated like -c VALUE\n\
or -c +VALUE.\n\
-FIXME: describe name vs descriptor\n\
-"));
+\n\
+With --follow (-f), tail defaults to following the file descriptor, which\n\
+means that even if a tail'ed file is renamed, tail will continue to track\n\
+its end. This default behavior is not desirable when you really want to\n\
+track the actual name of the file, not the file descriptor (e.g., log\n\
+rotation). Use --follow=name in that case. That causes tail to track the\n\
+named file by reopening it periodically to see if it has been removed and\n\
+recreated by some other program.\n\
+\n\
+"),
+ DEFAULT_N_LINES, DEFAULT_N_LINES,
+ DEFAULT_MAX_N_UNCHANGED_STATS_BETWEEN_OPENS,
+ DEFAULT_MAX_N_CONSECUTIVE_SIZE_CHANGES
+ );
puts (_("\nReport bugs to <bug-textutils@gnu.org>."));
}
exit (status == 0 ? EXIT_SUCCESS : EXIT_FAILURE);
}
+static int
+valid_file_spec (struct File_spec const *f)
+{
+ /* Exactly one of the following subexpressions must be true. */
+ return ((f->fd == -1) ^ (f->errnum == 0));
+}
+
static char *
pretty_name (struct File_spec const *f)
{
int fd;
int fail = 0;
int is_stdin = (STREQ (f->name, "-"));
- int was_missing = f->missing;
+ int was_tailable = f->tailable;
int prev_errnum = f->errnum;
int new_file;
+ assert (valid_file_spec (f));
+
fd = (is_stdin ? STDIN_FILENO : open (f->name, O_RDONLY));
/* If the open fails because the file doesn't exist,
- then mark the file as missing. */
- f->missing = (allow_missing && fd == -1 && errno == ENOENT);
+ then mark the file as not tailable. */
+ f->tailable = !(reopen_inaccessible_files && fd == -1);
if (fd == -1 || fstat (fd, &new_stats) < 0)
{
fail = 1;
f->errnum = errno;
- if (f->missing)
+ if (!f->tailable)
{
- if (!was_missing)
- error (0, 0, "`%s' has been removed", pretty_name (f));
+ if (was_tailable)
+ {
+ /* FIXME-maybe: detect the case in which the file first becomes
+ unreadable (perms), and later becomes readable again and can
+ be seen to be the same file (dev/ino). Otherwise, tail prints
+ the entire contents of the file when it becomes readable. */
+ error (0, f->errnum, _("`%s' has become inaccessible"),
+ pretty_name (f));
+ }
else
{
- /* say nothing... it's still missing */
+ /* say nothing... it's still not tailable */
}
}
else if (prev_errnum != errno)
pretty_name (f));
}
else
- f->errnum = 0;
+ {
+ f->errnum = 0;
+ }
new_file = 0;
if (fail)
else if (prev_errnum && prev_errnum != ENOENT)
{
new_file = 1;
- if (f->fd != -1)
- close_fd (f->fd, pretty_name (f)); /* close the old handle */
+ /* FIXME-now: is this close ever necessary? */
+ close_fd (f->fd, pretty_name (f)); /* close the old handle */
error (0, 0, _("`%s' has become accessible"), pretty_name (f));
}
else if (f->ino != new_stats.st_ino || f->dev != new_stats.st_dev)
pretty_name (f));
}
}
- else if (f->missing)
- {
- new_file = 1;
- error (0, 0, _("`%s' has reappeared"), pretty_name (f));
- f->missing = 0;
- }
else
{
close_fd (fd, pretty_name (f));
COPY_TO_EOF);
}
- if (n_live_files (f, nfiles) == 0 && ! allow_missing)
+ if (n_live_files (f, nfiles) == 0 && ! reopen_inaccessible_files)
{
error (0, 0, _("no files remaining"));
break;
fd = open (f->name, O_RDONLY);
}
- f->missing = (allow_missing && fd == -1 && errno == ENOENT);
+ f->tailable = !(reopen_inaccessible_files && fd == -1);
if (fd == -1)
{
break;
case CHAR_MAX + 1:
- allow_missing = 1;
+ reopen_inaccessible_files = 1;
break;
case CHAR_MAX + 2:
usage (1);
}
}
+
+ if (reopen_inaccessible_files && follow_mode != Follow_name)
+ error (0, 0, _("warning: --retry is useful only when following by name"));
}
int
projects / thirdparty / coreutils.git / commitdiff
