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Include fcntl-safer.h.

Browse Source 
(COPY_TO_EOF): Set to UINTMAX_MAX, not OFF_T_MAX (which was wrong).
(COPY_A_BUFFER): New macro.
(struct File_spec): New members mtime, mode, blocking.
Remove member n_consecutive_size_changes.
(DEFAULT_MAX_N_CONSECUTIVE_SIZE_CHANGES,
max_n_consecutive_size_changes_between_opens,
MAX_CONSECUTIVE_SIZE_CHANGES_OPTION): Remove.
(long_options, tail_forever, parse_options):
Remove (non-)support for --max-consecutive-size-changes.
(record_open_fd): New function.
(recheck, tail_file): Use it.  Don't assume that stdin is open.
(dump_remainder): Add support for new COPY_A_BUFFER special value.
Treat errno==EAGAIN like EOF, since it might be a nonblocking read.
(recheck): New arg BLOCKING, specifying whether to use blocking reads.
All uses changed.
(n_live_files): Remove, replacing with...
(any_live_files): New function.  All uses changed.
(tail_forever): Use nonblocking I/O unless we know that blocking I/O
is safe; this avoids some hangs when reading from a fifo.
Avoid invoking fstat or sleep when using blocking I/O.
Do not check for changes to size if the file is not a regular file,
as the size is undefined in that case.
Check for changes to mtime or mode, too; this works for non-regular
files.
(tail_forever, main): Redo fflush strategy to work even when input
is nonblocking.  Don't use unbuffered output; just flush when needed.
This commit is contained in:
Paul Eggert
2004-07-23 22:33:51 +00:00
parent 61b792fc38
commit 441462ac72
1 changed files with 144 additions and 138 deletions
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282
src/tail.c
View File

@@ -35,6 +35,7 @@
#include "argmatch.h"
#include "c-strtod.h"
#include "error.h"
#include "fcntl-safer.h"
#include "inttostr.h"
#include "posixver.h"
#include "quote.h"
@@ -58,8 +59,9 @@
/* Number of items to tail. */
#define DEFAULT_N_LINES 10
/* A special value for dump_remainder's N_BYTES parameter. */
#define COPY_TO_EOF OFF_T_MAX
/* Special values for dump_remainder's N_BYTES parameter. */
#define COPY_TO_EOF UINTMAX_MAX
#define COPY_A_BUFFER (UINTMAX_MAX - 1)
/* FIXME: make Follow_name the default? */
#define DEFAULT_FOLLOW_MODE Follow_descriptor
@@ -99,12 +101,15 @@ struct File_spec
/* File descriptor on which the file is open; -1 if it's not open. */
int fd;
/* The size of the file the last time we checked. */
/* Attributes of the file the last time we checked. */
off_t size;
/* The device and inode of the file the last time we checked. */
struct timespec mtime;
dev_t dev;
ino_t ino;
mode_t mode;
/* 1 if O_NONBLOCK is clear, 0 if set, -1 if not known. */
int blocking;
/* The specified name initially referred to a directory or some other
type for which tail isn't meaningful. Unlike for a permission problem
@@ -114,9 +119,6 @@ struct File_spec
/* See description of DEFAULT_MAX_N_... below. */
unsigned int n_unchanged_stats;
/* See description of DEFAULT_MAX_N_... below. */
unsigned int n_consecutive_size_changes;
/* A file is tailable if it exists, is readable, and is of type
IS_TAILABLE_FILE_TYPE. */
int tailable;
@@ -154,7 +156,7 @@ enum header_mode
};
/* When tailing a file by name, if there have been this many consecutive
iterations for which the size has remained the same, then open/fstat
iterations for which the file has not changed, 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 */
@@ -162,16 +164,6 @@ enum header_mode
static unsigned long max_n_unchanged_stats_between_opens =
DEFAULT_MAX_N_UNCHANGED_STATS_BETWEEN_OPENS;
/* This variable is used to ensure that a file that is unlinked or moved
aside, yet always growing will be recognized as having been renamed.
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-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;
@@ -194,11 +186,6 @@ enum
RETRY_OPTION = CHAR_MAX + 1,
ALLOW_MISSING_OPTION, /* deprecated, FIXME: remove in late 2004 */
MAX_UNCHANGED_STATS_OPTION,
/* FIXME: remove this in 2001, unless someone can show a good
reason to keep it. */
MAX_CONSECUTIVE_SIZE_CHANGES_OPTION,
PID_OPTION,
PRESUME_INPUT_PIPE_OPTION,
LONG_FOLLOW_OPTION
@@ -212,8 +199,6 @@ static struct option const long_options[] =
{"follow", optional_argument, NULL, LONG_FOLLOW_OPTION},
{"lines", required_argument, NULL, 'n'},
{"max-unchanged-stats", required_argument, NULL, MAX_UNCHANGED_STATS_OPTION},
{"max-consecutive-size-changes", required_argument, NULL,
MAX_CONSECUTIVE_SIZE_CHANGES_OPTION},
{"pid", required_argument, NULL, PID_OPTION},
{"presume-input-pipe", no_argument, NULL,
PRESUME_INPUT_PIPE_OPTION}, /* do not document */
@@ -327,6 +312,28 @@ xwrite (int fd, char const *buffer, size_t n_bytes)
error (EXIT_FAILURE, errno, _("write error"));
}
/* Record a file F with descriptor FD, size SIZE, status ST, and
blocking status BLOCKING. */
static void
record_open_fd (struct File_spec *f, int fd,
off_t size, struct stat const *st,
int blocking)
{
f->fd = fd;
f->size = size;
f->mtime.tv_sec = st->st_mtime;
f->mtime.tv_nsec = TIMESPEC_NS (st->st_mtim);
f->dev = st->st_dev;
f->ino = st->st_ino;
f->mode = st->st_mode;
f->blocking = blocking;
f->n_unchanged_stats = 0;
f->ignore = 0;
}
/* Close the file with descriptor FD and name FILENAME. */
static void
close_fd (int fd, const char *filename)
{
@@ -347,6 +354,7 @@ write_header (const char *pretty_filename)
/* Read and output N_BYTES of file PRETTY_FILENAME starting at the current
position in FD. If N_BYTES is COPY_TO_EOF, then copy until end of file.
If N_BYTES is COPY_A_BUFFER, then copy at most one buffer's worth.
Return the number of bytes read from the file. */
static uintmax_t
@@ -362,13 +370,22 @@ dump_remainder (const char *pretty_filename, int fd, uintmax_t n_bytes)
size_t n = MIN (n_remaining, BUFSIZ);
size_t bytes_read = safe_read (fd, buffer, n);
if (bytes_read == SAFE_READ_ERROR)
error (EXIT_FAILURE, errno, _("error reading %s"),
quote (pretty_filename));
{
if (errno != EAGAIN)
error (EXIT_FAILURE, errno, _("error reading %s"),
quote (pretty_filename));
break;
}
if (bytes_read == 0)
break;
xwrite (STDOUT_FILENO, buffer, bytes_read);
n_remaining -= bytes_read;
n_written += bytes_read;
if (n_bytes != COPY_TO_EOF)
{
n_remaining -= bytes_read;
if (n_remaining == 0 || n_bytes == COPY_A_BUFFER)
break;
}
}
return n_written;
@@ -822,21 +839,21 @@ start_lines (const char *pretty_filename, int fd, uintmax_t n_lines,
/* FIXME: describe */
static void
recheck (struct File_spec *f)
recheck (struct File_spec *f, bool blocking)
{
/* open/fstat the file and announce if dev/ino have changed */
struct stat new_stats;
int fd;
int fail = 0;
int is_stdin = (STREQ (f->name, "-"));
int was_tailable = f->tailable;
int prev_errnum = f->errnum;
int new_file;
int fd = (is_stdin
? STDIN_FILENO
: open_safer (f->name, O_RDONLY | (blocking ? 0 : O_NONBLOCK)));
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 not tailable. */
f->tailable = !(reopen_inaccessible_files && fd == -1);
@@ -931,32 +948,24 @@ recheck (struct File_spec *f)
if (new_file)
{
/* Record new file info in f. */
f->fd = fd;
f->size = 0; /* Start at the beginning of the file... */
f->dev = new_stats.st_dev;
f->ino = new_stats.st_ino;
f->n_unchanged_stats = 0;
f->n_consecutive_size_changes = 0;
f->ignore = 0;
xlseek (f->fd, f->size, SEEK_SET, pretty_name (f));
/* Start at the beginning of the file. */
record_open_fd (f, fd, 0, &new_stats, (is_stdin ? -1 : blocking));
xlseek (fd, 0, SEEK_SET, pretty_name (f));
}
}
/* FIXME: describe */
/* Return true if any of the N_FILES files in F are live, i.e., have
open file descriptors. */
static unsigned int
n_live_files (const struct File_spec *f, int n_files)
static bool
any_live_files (const struct File_spec *f, int n_files)
{
int i;
unsigned int n_live = 0;
for (i = 0; i < n_files; i++)
{
if (f[i].fd >= 0)
++n_live;
}
return n_live;
if (0 <= f[i].fd)
return true;
return false;
}
/* Tail NFILES files forever, or until killed.
@@ -969,6 +978,9 @@ n_live_files (const struct File_spec *f, int n_files)
static void
tail_forever (struct File_spec *f, int nfiles, double sleep_interval)
{
/* Use blocking I/O as an optimization, when it's easy. */
bool blocking = (pid == 0 && follow_mode == Follow_descriptor
&& nfiles == 1 && ! S_ISREG (f[0].mode));
int last;
int writer_is_dead = 0;
@@ -977,90 +989,110 @@ tail_forever (struct File_spec *f, int nfiles, double sleep_interval)
while (1)
{
int i;
int any_changed;
bool any_input = false;
any_changed = 0;
for (i = 0; i < nfiles; i++)
{
int fd;
char const *name;
mode_t mode;
struct stat stats;
uintmax_t bytes_read;
if (f[i].ignore)
continue;
if (f[i].fd < 0)
{
recheck (&f[i]);
recheck (&f[i], blocking);
continue;
}
if (fstat (f[i].fd, &stats) < 0)
fd = f[i].fd;
name = pretty_name (&f[i]);
mode = f[i].mode;
if (f[i].blocking != blocking)
{
f[i].fd = -1;
f[i].errnum = errno;
error (0, errno, "%s", pretty_name (&f[i]));
continue;
int old_flags = fcntl (fd, F_GETFL);
int new_flags = old_flags | (blocking ? 0 : O_NONBLOCK);
if (old_flags < 0
|| (new_flags != old_flags
&& fcntl (fd, F_SETFL, new_flags) == -1))
error (EXIT_FAILURE, errno,
_("%s: cannot change nonblocking mode"), name);
f[i].blocking = blocking;
}
if (stats.st_size == f[i].size)
if (!blocking)
{
f[i].n_consecutive_size_changes = 0;
if ((max_n_unchanged_stats_between_opens
<= f[i].n_unchanged_stats++)
&& follow_mode == Follow_name)
if (fstat (fd, &stats) != 0)
{
recheck (&f[i]);
f[i].n_unchanged_stats = 0;
f[i].fd = -1;
f[i].errnum = errno;
error (0, errno, "%s", name);
continue;
}
if ((! S_ISREG (stats.st_mode) || f[i].size == stats.st_size)
&& f[i].mtime.tv_sec == stats.st_mtime
&& f[i].mtime.tv_nsec == TIMESPEC_NS (stats.st_mtim)
&& f[i].mode == stats.st_mode)
{
if ((max_n_unchanged_stats_between_opens
<= f[i].n_unchanged_stats++)
&& follow_mode == Follow_name)
{
recheck (&f[i], blocking);
f[i].n_unchanged_stats = 0;
}
continue;
}
/* This file has changed. Print out what we can, and
then keep looping. */
f[i].mtime.tv_sec = stats.st_mtime;
f[i].mtime.tv_nsec = TIMESPEC_NS (stats.st_mtim);
f[i].mode = stats.st_mode;
/* reset counter */
f[i].n_unchanged_stats = 0;
if (S_ISREG (mode) && stats.st_size < f[i].size)
{
error (0, 0, _("%s: file truncated"), name);
last = i;
xlseek (fd, stats.st_size, SEEK_SET, name);
f[i].size = stats.st_size;
continue;
}
if (i != last)
{
if (print_headers)
write_header (name);
last = i;
}
continue;
}
/* Ensure that a file that's unlinked or moved aside, yet always
growing will be recognized as having been renamed. */
if ((max_n_consecutive_size_changes_between_opens
<= f[i].n_consecutive_size_changes++)
&& follow_mode == Follow_name)
{
f[i].n_consecutive_size_changes = 0;
recheck (&f[i]);
continue;
}
/* This file has changed size. Print out what we can, and
then keep looping. */
any_changed = 1;
/* reset counter */
f[i].n_unchanged_stats = 0;
if (stats.st_size < f[i].size)
{
error (0, 0, _("%s: file truncated"), pretty_name (&f[i]));
last = i;
xlseek (f[i].fd, (off_t) stats.st_size, SEEK_SET,
pretty_name (&f[i]));
f[i].size = stats.st_size;
continue;
}
if (i != last)
{
if (print_headers)
write_header (pretty_name (&f[i]));
last = i;
}
f[i].size += dump_remainder (pretty_name (&f[i]), f[i].fd,
COPY_TO_EOF);
bytes_read = dump_remainder (name, fd,
blocking ? COPY_A_BUFFER : COPY_TO_EOF);
any_input |= (bytes_read != 0);
f[i].size += bytes_read;
}
if (n_live_files (f, nfiles) == 0 && ! reopen_inaccessible_files)
if (! any_live_files (f, nfiles) && ! reopen_inaccessible_files)
{
error (0, 0, _("no files remaining"));
break;
}
/* If none of the files changed size, sleep. */
if (!any_changed)
if ((!any_input | blocking) && fflush (stdout) != 0)
error (EXIT_FAILURE, errno, _("write error"));
/* If nothing was read, sleep and/or check for dead writers. */
if (!any_input)
{
if (writer_is_dead)
break;
@@ -1189,8 +1221,8 @@ tail_lines (const char *pretty_filename, int fd, uintmax_t n_lines,
which lseek (... SEEK_END) works. */
if ( ! presume_input_pipe
&& S_ISREG (stats.st_mode)
&& (start_pos = lseek (fd, (off_t) 0, SEEK_CUR)) != -1
&& start_pos < (end_pos = lseek (fd, (off_t) 0, SEEK_END)))
&& (start_pos = lseek (fd, 0, SEEK_CUR)) != -1
&& start_pos < (end_pos = lseek (fd, 0, SEEK_END)))
{
*read_pos = end_pos;
if (end_pos != 0 && file_lines (pretty_filename, fd, n_lines,
@@ -1250,7 +1282,7 @@ tail_file (struct File_spec *f, uintmax_t n_units)
}
else
{
fd = open (f->name, O_RDONLY);
fd = open_safer (f->name, O_RDONLY);
}
f->tailable = !(reopen_inaccessible_files && fd == -1);
@@ -1310,17 +1342,10 @@ tail_file (struct File_spec *f, uintmax_t n_units)
}
else
{
f->fd = fd;
/* Note: we must use read_pos here, not stats.st_size,
to avoid a race condition described by Ken Raeburn:
http://mail.gnu.org/archive/html/bug-textutils/2003-05/msg00007.html */
f->size = read_pos;
f->dev = stats.st_dev;
f->ino = stats.st_ino;
f->n_unchanged_stats = 0;
f->n_consecutive_size_changes = 0;
f->ignore = 0;
record_open_fd (f, fd, read_pos, &stats, (is_stdin ? -1 : 1));
}
}
else
@@ -1553,18 +1578,6 @@ parse_options (int argc, char **argv,
}
break;
case MAX_CONSECUTIVE_SIZE_CHANGES_OPTION:
/* --max-consecutive-size-changes=N */
if (xstrtoul (optarg, NULL, 10,
&max_n_consecutive_size_changes_between_opens, "")
!= LONGINT_OK)
{
error (EXIT_FAILURE, 0,
_("%s: invalid maximum number of consecutive size changes"),
optarg);
}
break;
case PID_OPTION:
{
strtol_error s_err;
@@ -1729,14 +1742,7 @@ main (int argc, char **argv)
exit_status |= tail_file (&F[i], n_units);
if (forever)
{
/* This fflush appears to be required only on Solaris 5.7. */
if (fflush (stdout) < 0)
error (EXIT_FAILURE, errno, _("write error"));
SETVBUF (stdout, NULL, _IONBF, 0);
tail_forever (F, n_files, sleep_interval);
}
tail_forever (F, n_files, sleep_interval);
if (have_read_stdin && close (STDIN_FILENO) < 0)
error (EXIT_FAILURE, errno, "-");