diff options
Diffstat (limited to 'src/tail.c')
| -rw-r--r-- | src/tail.c | 2086 |
1 files changed, 1397 insertions, 689 deletions
@@ -1,10 +1,10 @@ /* tail -- output the last part of file(s) - Copyright (C) 1989, 90, 91, 1995-2006 Free Software Foundation, Inc. + Copyright (C) 1989-2016 Free Software Foundation, Inc. - This program is free software; you can redistribute it and/or modify + This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by - the Free Software Foundation; either version 2, or (at your option) - any later version. + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of @@ -12,8 +12,7 @@ GNU General Public License for more details. You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software Foundation, - Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + along with this program. If not, see <http://www.gnu.org/licenses/>. */ /* Can display any amount of data, unlike the Unix version, which uses a fixed size buffer and therefore can only deliver a limited number @@ -21,7 +20,8 @@ Original version by Paul Rubin <phr@ocf.berkeley.edu>. Extensions by David MacKenzie <djm@gnu.ai.mit.edu>. - tail -f for multiple files by Ian Lance Taylor <ian@airs.com>. */ + tail -f for multiple files by Ian Lance Taylor <ian@airs.com>. + inotify back-end by Giuseppe Scrivano <gscrivano@gnu.org>. */ #include <config.h> @@ -36,21 +36,42 @@ #include "c-strtod.h" #include "error.h" #include "fcntl--.h" -#include "inttostr.h" #include "isapipe.h" #include "posixver.h" #include "quote.h" #include "safe-read.h" +#include "stat-size.h" #include "stat-time.h" +#include "xfreopen.h" #include "xnanosleep.h" +#include "xdectoint.h" #include "xstrtol.h" #include "xstrtod.h" -/* The official name of this program (e.g., no `g' prefix). */ +#if HAVE_INOTIFY +# include "hash.h" +# include <sys/inotify.h> +/* 'select' is used by tail_forever_inotify. */ +# include <sys/select.h> + +/* inotify needs to know if a file is local. */ +# include "fs.h" +# include "fs-is-local.h" +# if HAVE_SYS_STATFS_H +# include <sys/statfs.h> +# elif HAVE_SYS_VFS_H +# include <sys/vfs.h> +# endif +#endif + +/* The official name of this program (e.g., no 'g' prefix). */ #define PROGRAM_NAME "tail" #define AUTHORS \ - "Paul Rubin", "David MacKenzie, Ian Lance Taylor", "Jim Meyering" + proper_name ("Paul Rubin"), \ + proper_name ("David MacKenzie"), \ + proper_name ("Ian Lance Taylor"), \ + proper_name ("Jim Meyering") /* Number of items to tail. */ #define DEFAULT_N_LINES 10 @@ -94,9 +115,6 @@ struct File_spec /* The actual file name, or "-" for stdin. */ char *name; - /* File descriptor on which the file is open; -1 if it's not open. */ - int fd; - /* Attributes of the file the last time we checked. */ off_t size; struct timespec mtime; @@ -104,24 +122,41 @@ struct File_spec 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 (tailable, below) once this is set, the name is not checked ever again. */ bool ignore; - /* See description of DEFAULT_MAX_N_... below. */ - uintmax_t n_unchanged_stats; + /* See the description of fremote. */ + bool remote; /* A file is tailable if it exists, is readable, and is of type IS_TAILABLE_FILE_TYPE. */ bool tailable; + /* File descriptor on which the file is open; -1 if it's not open. */ + int fd; + /* The value of errno seen last time we checked this file. */ int errnum; + /* 1 if O_NONBLOCK is clear, 0 if set, -1 if not known. */ + int blocking; + +#if HAVE_INOTIFY + /* The watch descriptor used by inotify. */ + int wd; + + /* The parent directory watch descriptor. It is used only + * when Follow_name is used. */ + int parent_wd; + + /* Offset in NAME of the basename part. */ + size_t basename_start; +#endif + + /* See description of DEFAULT_MAX_N_... below. */ + uintmax_t n_unchanged_stats; }; /* Keep trying to open a file even if it is inaccessible when tail starts @@ -145,6 +180,9 @@ static bool from_start; /* If true, print filename headers. */ static bool print_headers; +/* Character to split lines by. */ +static char line_end; + /* When to print the filename banners. */ enum header_mode { @@ -160,9 +198,6 @@ enum header_mode static uintmax_t max_n_unchanged_stats_between_opens = DEFAULT_MAX_N_UNCHANGED_STATS_BETWEEN_OPENS; -/* The name this program was run with. */ -char *program_name; - /* The process ID of the process (presumably on the current host) that is writing to all followed files. */ static pid_t pid; @@ -175,6 +210,9 @@ static bool have_read_stdin; more expensive) code unconditionally. Intended solely for testing. */ static bool presume_input_pipe; +/* If nonzero then don't use inotify even if available. */ +static bool disable_inotify; + /* For long options that have no equivalent short option, use a non-character as a pseudo short option, starting with CHAR_MAX + 1. */ enum @@ -183,7 +221,8 @@ enum MAX_UNCHANGED_STATS_OPTION, PID_OPTION, PRESUME_INPUT_PIPE_OPTION, - LONG_FOLLOW_OPTION + LONG_FOLLOW_OPTION, + DISABLE_INOTIFY_OPTION }; static struct option const long_options[] = @@ -192,6 +231,8 @@ 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}, + {"-disable-inotify", no_argument, NULL, + DISABLE_INOTIFY_OPTION}, /* do not document */ {"pid", required_argument, NULL, PID_OPTION}, {"-presume-input-pipe", no_argument, NULL, PRESUME_INPUT_PIPE_OPTION}, /* do not document */ @@ -200,6 +241,7 @@ static struct option const long_options[] = {"silent", no_argument, NULL, 'q'}, {"sleep-interval", required_argument, NULL, 's'}, {"verbose", no_argument, NULL, 'v'}, + {"zero-terminated", no_argument, NULL, 'z'}, {GETOPT_HELP_OPTION_DECL}, {GETOPT_VERSION_OPTION_DECL}, {NULL, 0, NULL, 0} @@ -209,80 +251,77 @@ void usage (int status) { if (status != EXIT_SUCCESS) - fprintf (stderr, _("Try `%s --help' for more information.\n"), - program_name); + emit_try_help (); else { printf (_("\ Usage: %s [OPTION]... [FILE]...\n\ "), - program_name); + program_name); printf (_("\ 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\ "), DEFAULT_N_LINES); + + emit_stdin_note (); + emit_mandatory_arg_note (); + fputs (_("\ -Mandatory arguments to long options are mandatory for short options too.\n\ -"), stdout); - fputs (_("\ - --retry keep trying to open a file even if it is\n\ - inaccessible when tail starts or if it becomes\n\ - inaccessible later; useful when following by name,\n\ - i.e., with --follow=name\n\ - -c, --bytes=N output the last N bytes; alternatively, use +N to\n\ - output bytes starting with the Nth of each file\n\ + -c, --bytes=[+]NUM output the last NUM bytes; or use -c +NUM to\n\ + output starting with byte NUM of each file\n\ "), stdout); fputs (_("\ -f, --follow[={name|descriptor}]\n\ output appended data as the file grows;\n\ - -f, --follow, and --follow=descriptor are\n\ - equivalent\n\ + an absent option argument means 'descriptor'\n\ -F same as --follow=name --retry\n\ "), stdout); printf (_("\ - -n, --lines=N output the last N lines, instead of the last %d;\n\ - or use +N to output lines starting with the Nth\n\ + -n, --lines=[+]NUM output the last NUM lines, instead of the last %d;\n\ + or use -n +NUM to output starting with line NUM\n\ --max-unchanged-stats=N\n\ with --follow=name, reopen a FILE which has not\n\ - changed size after N (default %d) iterations\n\ - to see if it has been unlinked or renamed\n\ - (this is the usual case of rotated log files)\n\ + changed size after N (default %d) iterations\n\ + to see if it has been unlinked or renamed\n\ + (this is the usual case of rotated log files);\n\ + with inotify, this option is rarely useful\n\ "), - DEFAULT_N_LINES, - DEFAULT_MAX_N_UNCHANGED_STATS_BETWEEN_OPENS - ); + DEFAULT_N_LINES, + DEFAULT_MAX_N_UNCHANGED_STATS_BETWEEN_OPENS + ); fputs (_("\ --pid=PID with -f, terminate after process ID, PID dies\n\ -q, --quiet, --silent never output headers giving file names\n\ - -s, --sleep-interval=S with -f, sleep for approximately S seconds\n\ - (default 1.0) between iterations.\n\ + --retry keep trying to open a file if it is inaccessible\n\ +"), stdout); + fputs (_("\ + -s, --sleep-interval=N with -f, sleep for approximately N seconds\n\ + (default 1.0) between iterations;\n\ + with inotify and --pid=P, check process P at\n\ + least once every N seconds\n\ -v, --verbose always output headers giving file names\n\ "), stdout); + fputs (_("\ + -z, --zero-terminated line delimiter is NUL, not newline\n\ +"), stdout); fputs (HELP_OPTION_DESCRIPTION, stdout); fputs (VERSION_OPTION_DESCRIPTION, stdout); fputs (_("\ \n\ -If the first character of N (the number of bytes or lines) is a `+',\n\ -print beginning with the Nth item from the start of each file, otherwise,\n\ -print the last N items in the file. N may have a multiplier suffix:\n\ -b 512, k 1024, m 1024*1024.\n\ +NUM may have a multiplier suffix:\n\ +b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024,\n\ +GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.\n\ \n\ "), stdout); fputs (_("\ 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. \ -"), stdout); - fputs (_("\ -This default behavior is not desirable when you really want to\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\ +named file in a way that accommodates renaming, removal and creation.\n\ "), stdout); - printf (_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT); + emit_ancillary_info (PROGRAM_NAME); } exit (status); } @@ -297,14 +336,7 @@ valid_file_spec (struct File_spec const *f) static char const * pretty_name (struct File_spec const *f) { - return (STREQ (f->name, "-") ? "standard input" : f->name); -} - -static void -xwrite_stdout (char const *buffer, size_t n_bytes) -{ - if (n_bytes > 0 && fwrite (buffer, 1, n_bytes, stdout) == 0) - error (EXIT_FAILURE, errno, _("write error")); + return (STREQ (f->name, "-") ? _("standard input") : f->name); } /* Record a file F with descriptor FD, size SIZE, status ST, and @@ -312,8 +344,8 @@ xwrite_stdout (char const *buffer, size_t n_bytes) static void record_open_fd (struct File_spec *f, int fd, - off_t size, struct stat const *st, - int blocking) + off_t size, struct stat const *st, + int blocking) { f->fd = fd; f->size = size; @@ -323,7 +355,7 @@ record_open_fd (struct File_spec *f, int fd, f->mode = st->st_mode; f->blocking = blocking; f->n_unchanged_stats = 0; - f->ignore = 0; + f->ignore = false; } /* Close the file with descriptor FD and name FILENAME. */ @@ -333,7 +365,7 @@ close_fd (int fd, const char *filename) { if (fd != -1 && fd != STDIN_FILENO && close (fd)) { - error (0, errno, _("closing %s (fd=%d)"), filename, fd); + error (0, errno, _("closing %s (fd=%d)"), quoteaf (filename), fd); } } @@ -346,6 +378,20 @@ write_header (const char *pretty_filename) first_file = false; } +/* Write N_BYTES from BUFFER to stdout. + Exit immediately on error with a single diagnostic. */ + +static void +xwrite_stdout (char const *buffer, size_t n_bytes) +{ + if (n_bytes > 0 && fwrite (buffer, 1, n_bytes, stdout) < n_bytes) + { + clearerr (stdout); /* To avoid redundant close_stdout diagnostic. */ + error (EXIT_FAILURE, errno, _("error writing %s"), + quoteaf ("standard output")); + } +} + /* 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. @@ -364,22 +410,22 @@ 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) - { - if (errno != EAGAIN) - error (EXIT_FAILURE, errno, _("error reading %s"), - quote (pretty_filename)); - break; - } + { + if (errno != EAGAIN) + error (EXIT_FAILURE, errno, _("error reading %s"), + quoteaf (pretty_filename)); + break; + } if (bytes_read == 0) - break; + break; xwrite_stdout (buffer, 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; - } + { + n_remaining -= bytes_read; + if (n_remaining == 0 || n_bytes == COPY_A_BUFFER) + break; + } } return n_written; @@ -394,7 +440,7 @@ static off_t xlseek (int fd, off_t offset, int whence, char const *filename) { off_t new_offset = lseek (fd, offset, whence); - char buf[INT_BUFSIZE_BOUND (off_t)]; + char buf[INT_BUFSIZE_BOUND (offset)]; char *s; if (0 <= new_offset) @@ -405,15 +451,15 @@ xlseek (int fd, off_t offset, int whence, char const *filename) { case SEEK_SET: error (0, errno, _("%s: cannot seek to offset %s"), - filename, s); + quotef (filename), s); break; case SEEK_CUR: error (0, errno, _("%s: cannot seek to relative offset %s"), - filename, s); + quotef (filename), s); break; case SEEK_END: error (0, errno, _("%s: cannot seek to end-relative offset %s"), - filename, s); + quotef (filename), s); break; default: abort (); @@ -423,7 +469,7 @@ xlseek (int fd, off_t offset, int whence, char const *filename) } /* Print the last N_LINES lines from the end of file FD. - Go backward through the file, reading `BUFSIZ' bytes at a time (except + Go backward through the file, reading 'BUFSIZ' bytes at a time (except probably the first), until we hit the start of the file or have read NUMBER newlines. START_POS is the starting position of the read pointer for the file @@ -433,7 +479,7 @@ xlseek (int fd, off_t offset, int whence, char const *filename) static bool file_lines (const char *pretty_filename, int fd, uintmax_t n_lines, - off_t start_pos, off_t end_pos, uintmax_t *read_pos) + off_t start_pos, off_t end_pos, uintmax_t *read_pos) { char buffer[BUFSIZ]; size_t bytes_read; @@ -442,25 +488,25 @@ file_lines (const char *pretty_filename, int fd, uintmax_t n_lines, if (n_lines == 0) return true; - /* Set `bytes_read' to the size of the last, probably partial, buffer; - 0 < `bytes_read' <= `BUFSIZ'. */ + /* Set 'bytes_read' to the size of the last, probably partial, buffer; + 0 < 'bytes_read' <= 'BUFSIZ'. */ bytes_read = (pos - start_pos) % BUFSIZ; if (bytes_read == 0) bytes_read = BUFSIZ; - /* Make `pos' a multiple of `BUFSIZ' (0 if the file is short), so that all + /* Make 'pos' a multiple of 'BUFSIZ' (0 if the file is short), so that all reads will be on block boundaries, which might increase efficiency. */ pos -= bytes_read; xlseek (fd, pos, SEEK_SET, pretty_filename); bytes_read = safe_read (fd, buffer, bytes_read); if (bytes_read == SAFE_READ_ERROR) { - error (0, errno, _("error reading %s"), quote (pretty_filename)); + error (0, errno, _("error reading %s"), quoteaf (pretty_filename)); return false; } *read_pos = pos + bytes_read; /* Count the incomplete line on files that don't end with a newline. */ - if (bytes_read && buffer[bytes_read - 1] != '\n') + if (bytes_read && buffer[bytes_read - 1] != line_end) --n_lines; do @@ -469,43 +515,43 @@ file_lines (const char *pretty_filename, int fd, uintmax_t n_lines, size_t n = bytes_read; while (n) - { - char const *nl; - nl = memrchr (buffer, '\n', n); - if (nl == NULL) - break; - n = nl - buffer; - if (n_lines-- == 0) - { - /* If this newline isn't the last character in the buffer, - output the part that is after it. */ - if (n != bytes_read - 1) - xwrite_stdout (nl + 1, bytes_read - (n + 1)); - *read_pos += dump_remainder (pretty_filename, fd, - end_pos - (pos + bytes_read)); - return true; - } - } + { + char const *nl; + nl = memrchr (buffer, line_end, n); + if (nl == NULL) + break; + n = nl - buffer; + if (n_lines-- == 0) + { + /* If this newline isn't the last character in the buffer, + output the part that is after it. */ + if (n != bytes_read - 1) + xwrite_stdout (nl + 1, bytes_read - (n + 1)); + *read_pos += dump_remainder (pretty_filename, fd, + end_pos - (pos + bytes_read)); + return true; + } + } /* Not enough newlines in that bufferfull. */ if (pos == start_pos) - { - /* Not enough lines in the file; print everything from - start_pos to the end. */ - xlseek (fd, start_pos, SEEK_SET, pretty_filename); - *read_pos = start_pos + dump_remainder (pretty_filename, fd, - end_pos); - return true; - } + { + /* Not enough lines in the file; print everything from + start_pos to the end. */ + xlseek (fd, start_pos, SEEK_SET, pretty_filename); + *read_pos = start_pos + dump_remainder (pretty_filename, fd, + end_pos); + return true; + } pos -= BUFSIZ; xlseek (fd, pos, SEEK_SET, pretty_filename); bytes_read = safe_read (fd, buffer, BUFSIZ); if (bytes_read == SAFE_READ_ERROR) - { - error (0, errno, _("error reading %s"), quote (pretty_filename)); - return false; - } + { + error (0, errno, _("error reading %s"), quoteaf (pretty_filename)); + return false; + } *read_pos = pos + bytes_read; } @@ -521,7 +567,7 @@ file_lines (const char *pretty_filename, int fd, uintmax_t n_lines, static bool pipe_lines (const char *pretty_filename, int fd, uintmax_t n_lines, - uintmax_t *read_pos) + uintmax_t *read_pos) { struct linebuffer { @@ -546,7 +592,7 @@ pipe_lines (const char *pretty_filename, int fd, uintmax_t n_lines, { n_read = safe_read (fd, tmp->buffer, BUFSIZ); if (n_read == 0 || n_read == SAFE_READ_ERROR) - break; + break; tmp->nbytes = n_read; *read_pos += n_read; tmp->nlines = 0; @@ -554,49 +600,49 @@ pipe_lines (const char *pretty_filename, int fd, uintmax_t n_lines, /* Count the number of newlines just read. */ { - char const *buffer_end = tmp->buffer + n_read; - char const *p = tmp->buffer; - while ((p = memchr (p, '\n', buffer_end - p))) - { - ++p; - ++tmp->nlines; - } + char const *buffer_end = tmp->buffer + n_read; + char const *p = tmp->buffer; + while ((p = memchr (p, line_end, buffer_end - p))) + { + ++p; + ++tmp->nlines; + } } total_lines += tmp->nlines; /* If there is enough room in the last buffer read, just append the new - one to it. This is because when reading from a pipe, `n_read' can + one to it. This is because when reading from a pipe, 'n_read' can often be very small. */ if (tmp->nbytes + last->nbytes < BUFSIZ) - { - memcpy (&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes); - last->nbytes += tmp->nbytes; - last->nlines += tmp->nlines; - } + { + memcpy (&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes); + last->nbytes += tmp->nbytes; + last->nlines += tmp->nlines; + } else - { - /* If there's not enough room, link the new buffer onto the end of - the list, then either free up the oldest buffer for the next - read if that would leave enough lines, or else malloc a new one. - Some compaction mechanism is possible but probably not - worthwhile. */ - last = last->next = tmp; - if (total_lines - first->nlines > n_lines) - { - tmp = first; - total_lines -= first->nlines; - first = first->next; - } - else - tmp = xmalloc (sizeof (LBUFFER)); - } + { + /* If there's not enough room, link the new buffer onto the end of + the list, then either free up the oldest buffer for the next + read if that would leave enough lines, or else malloc a new one. + Some compaction mechanism is possible but probably not + worthwhile. */ + last = last->next = tmp; + if (total_lines - first->nlines > n_lines) + { + tmp = first; + total_lines -= first->nlines; + first = first->next; + } + else + tmp = xmalloc (sizeof (LBUFFER)); + } } free (tmp); if (n_read == SAFE_READ_ERROR) { - error (0, errno, _("error reading %s"), quote (pretty_filename)); + error (0, errno, _("error reading %s"), quoteaf (pretty_filename)); ok = false; goto free_lbuffers; } @@ -610,7 +656,7 @@ pipe_lines (const char *pretty_filename, int fd, uintmax_t n_lines, goto free_lbuffers; /* Count the incomplete line on files that don't end with a newline. */ - if (last->buffer[last->nbytes - 1] != '\n') + if (last->buffer[last->nbytes - 1] != line_end) { ++last->nlines; ++total_lines; @@ -627,15 +673,15 @@ pipe_lines (const char *pretty_filename, int fd, uintmax_t n_lines, char const *buffer_end = tmp->buffer + tmp->nbytes; if (total_lines > n_lines) { - /* Skip `total_lines' - `n_lines' newlines. We made sure that - `total_lines' - `n_lines' <= `tmp->nlines'. */ - size_t j; - for (j = total_lines - n_lines; j; --j) - { - beg = memchr (beg, '\n', buffer_end - beg); - assert (beg); - ++beg; - } + /* Skip 'total_lines' - 'n_lines' newlines. We made sure that + 'total_lines' - 'n_lines' <= 'tmp->nlines'. */ + size_t j; + for (j = total_lines - n_lines; j; --j) + { + beg = memchr (beg, line_end, buffer_end - beg); + assert (beg); + ++beg; + } } xwrite_stdout (beg, buffer_end - beg); @@ -660,7 +706,7 @@ free_lbuffers: static bool pipe_bytes (const char *pretty_filename, int fd, uintmax_t n_bytes, - uintmax_t *read_pos) + uintmax_t *read_pos) { struct charbuffer { @@ -685,46 +731,46 @@ pipe_bytes (const char *pretty_filename, int fd, uintmax_t n_bytes, { n_read = safe_read (fd, tmp->buffer, BUFSIZ); if (n_read == 0 || n_read == SAFE_READ_ERROR) - break; + break; *read_pos += n_read; tmp->nbytes = n_read; tmp->next = NULL; total_bytes += tmp->nbytes; /* If there is enough room in the last buffer read, just append the new - one to it. This is because when reading from a pipe, `nbytes' can + one to it. This is because when reading from a pipe, 'nbytes' can often be very small. */ if (tmp->nbytes + last->nbytes < BUFSIZ) - { - memcpy (&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes); - last->nbytes += tmp->nbytes; - } + { + memcpy (&last->buffer[last->nbytes], tmp->buffer, tmp->nbytes); + last->nbytes += tmp->nbytes; + } else - { - /* If there's not enough room, link the new buffer onto the end of - the list, then either free up the oldest buffer for the next - read if that would leave enough characters, or else malloc a new - one. Some compaction mechanism is possible but probably not - worthwhile. */ - last = last->next = tmp; - if (total_bytes - first->nbytes > n_bytes) - { - tmp = first; - total_bytes -= first->nbytes; - first = first->next; - } - else - { - tmp = xmalloc (sizeof (CBUFFER)); - } - } + { + /* If there's not enough room, link the new buffer onto the end of + the list, then either free up the oldest buffer for the next + read if that would leave enough characters, or else malloc a new + one. Some compaction mechanism is possible but probably not + worthwhile. */ + last = last->next = tmp; + if (total_bytes - first->nbytes > n_bytes) + { + tmp = first; + total_bytes -= first->nbytes; + first = first->next; + } + else + { + tmp = xmalloc (sizeof (CBUFFER)); + } + } } free (tmp); if (n_read == SAFE_READ_ERROR) { - error (0, errno, _("error reading %s"), quote (pretty_filename)); + error (0, errno, _("error reading %s"), quoteaf (pretty_filename)); ok = false; goto free_cbuffers; } @@ -735,7 +781,7 @@ pipe_bytes (const char *pretty_filename, int fd, uintmax_t n_bytes, total_bytes -= tmp->nbytes; /* Find the correct beginning, then print the rest of the file. - We made sure that `total_bytes' - `n_bytes' <= `tmp->nbytes'. */ + We made sure that 'total_bytes' - 'n_bytes' <= 'tmp->nbytes'. */ if (total_bytes > n_bytes) i = total_bytes - n_bytes; else @@ -761,7 +807,7 @@ free_cbuffers: static int start_bytes (const char *pretty_filename, int fd, uintmax_t n_bytes, - uintmax_t *read_pos) + uintmax_t *read_pos) { char buffer[BUFSIZ]; @@ -769,22 +815,22 @@ start_bytes (const char *pretty_filename, int fd, uintmax_t n_bytes, { size_t bytes_read = safe_read (fd, buffer, BUFSIZ); if (bytes_read == 0) - return -1; + return -1; if (bytes_read == SAFE_READ_ERROR) - { - error (0, errno, _("error reading %s"), quote (pretty_filename)); - return 1; - } - read_pos += bytes_read; + { + error (0, errno, _("error reading %s"), quoteaf (pretty_filename)); + return 1; + } + *read_pos += bytes_read; if (bytes_read <= n_bytes) - n_bytes -= bytes_read; + n_bytes -= bytes_read; else - { - size_t n_remaining = bytes_read - n_bytes; - if (n_remaining) - xwrite_stdout (&buffer[n_bytes], n_remaining); - break; - } + { + size_t n_remaining = bytes_read - n_bytes; + if (n_remaining) + xwrite_stdout (&buffer[n_bytes], n_remaining); + break; + } } return 0; @@ -796,7 +842,7 @@ start_bytes (const char *pretty_filename, int fd, uintmax_t n_bytes, static int start_lines (const char *pretty_filename, int fd, uintmax_t n_lines, - uintmax_t *read_pos) + uintmax_t *read_pos) { if (n_lines == 0) return 0; @@ -804,38 +850,86 @@ start_lines (const char *pretty_filename, int fd, uintmax_t n_lines, while (1) { char buffer[BUFSIZ]; - char *p = buffer; size_t bytes_read = safe_read (fd, buffer, BUFSIZ); - char *buffer_end = buffer + bytes_read; if (bytes_read == 0) /* EOF */ - return -1; + return -1; if (bytes_read == SAFE_READ_ERROR) /* error */ - { - error (0, errno, _("error reading %s"), quote (pretty_filename)); - return 1; - } + { + error (0, errno, _("error reading %s"), quoteaf (pretty_filename)); + return 1; + } + + char *buffer_end = buffer + bytes_read; *read_pos += bytes_read; - while ((p = memchr (p, '\n', buffer_end - p))) - { - ++p; - if (--n_lines == 0) - { - if (p < buffer_end) - xwrite_stdout (p, buffer_end - p); - return 0; - } - } + char *p = buffer; + while ((p = memchr (p, line_end, buffer_end - p))) + { + ++p; + if (--n_lines == 0) + { + if (p < buffer_end) + xwrite_stdout (p, buffer_end - p); + return 0; + } + } } } -/* FIXME: describe */ +#if HAVE_INOTIFY +/* Without inotify support, always return false. Otherwise, return false + when FD is open on a file known to reside on a local file system. + If fstatfs fails, give a diagnostic and return true. + If fstatfs cannot be called, return true. */ +static bool +fremote (int fd, const char *name) +{ + bool remote = true; /* be conservative (poll by default). */ + +# if HAVE_FSTATFS && HAVE_STRUCT_STATFS_F_TYPE && defined __linux__ + struct statfs buf; + int err = fstatfs (fd, &buf); + if (err != 0) + { + /* On at least linux-2.6.38, fstatfs fails with ENOSYS when FD + is open on a pipe. Treat that like a remote file. */ + if (errno != ENOSYS) + error (0, errno, _("cannot determine location of %s. " + "reverting to polling"), quoteaf (name)); + } + else + { + switch (is_local_fs_type (buf.f_type)) + { + case 0: + break; + case -1: + /* Treat unrecognized file systems as "remote", so caller polls. + Note README-release has instructions for syncing the internal + list with the latest Linux kernel file system constants. */ + break; + case 1: + remote = false; + break; + default: + assert (!"unexpected return value from is_local_fs_type"); + } + } +# endif + + return remote; +} +#else +/* Without inotify support, whether a file is remote is irrelevant. + Always return "false" in that case. */ +# define fremote(fd, name) false +#endif +/* open/fstat F->name and handle changes. */ static void recheck (struct File_spec *f, bool blocking) { - /* open/fstat the file and announce if dev/ino have changed */ struct stat new_stats; bool ok = true; bool is_stdin = (STREQ (f->name, "-")); @@ -843,8 +937,8 @@ recheck (struct File_spec *f, bool blocking) int prev_errnum = f->errnum; bool new_file; int fd = (is_stdin - ? STDIN_FILENO - : open (f->name, O_RDONLY | (blocking ? 0 : O_NONBLOCK))); + ? STDIN_FILENO + : open (f->name, O_RDONLY | (blocking ? 0 : O_NONBLOCK))); assert (valid_file_spec (f)); @@ -852,30 +946,41 @@ recheck (struct File_spec *f, bool blocking) then mark the file as not tailable. */ f->tailable = !(reopen_inaccessible_files && fd == -1); - if (fd == -1 || fstat (fd, &new_stats) < 0) + if (! disable_inotify && ! lstat (f->name, &new_stats) + && S_ISLNK (new_stats.st_mode)) + { + /* Diagnose the edge case where a regular file is changed + to a symlink. We avoid inotify with symlinks since + it's awkward to match between symlink name and target. */ + ok = false; + f->errnum = -1; + f->ignore = true; + + error (0, 0, _("%s has been replaced with a symbolic link. " + "giving up on this name"), quoteaf (pretty_name (f))); + } + else if (fd == -1 || fstat (fd, &new_stats) < 0) { ok = false; f->errnum = errno; if (!f->tailable) - { - 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"), - quote (pretty_name (f))); - } - else - { - /* say nothing... it's still not tailable */ - } - } + { + 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"), + quoteaf (pretty_name (f))); + } + else + { + /* say nothing... it's still not tailable */ + } + } else if (prev_errnum != errno) - { - error (0, errno, "%s", pretty_name (f)); - } + error (0, errno, "%s", quotef (pretty_name (f))); } else if (!IS_TAILABLE_FILE_TYPE (new_stats.st_mode)) { @@ -883,9 +988,18 @@ recheck (struct File_spec *f, bool blocking) f->errnum = -1; error (0, 0, _("%s has been replaced with an untailable file;\ giving up on this name"), - quote (pretty_name (f))); + quoteaf (pretty_name (f))); f->ignore = true; } + else if (!disable_inotify && fremote (fd, pretty_name (f))) + { + ok = false; + f->errnum = -1; + error (0, 0, _("%s has been replaced with a remote file. " + "giving up on this name"), quoteaf (pretty_name (f))); + f->ignore = true; + f->remote = true; + } else { f->errnum = 0; @@ -902,44 +1016,47 @@ recheck (struct File_spec *f, bool blocking) { new_file = true; assert (f->fd == -1); - error (0, 0, _("%s has become accessible"), quote (pretty_name (f))); + error (0, 0, _("%s has become accessible"), quoteaf (pretty_name (f))); + } + else if (f->fd == -1) + { + /* A new file even when inodes haven't changed as <dev,inode> + pairs can be reused, and we know the file was missing + on the previous iteration. Note this also means the file + is redisplayed in --follow=name mode if renamed away from + and back to a monitored name. */ + new_file = true; + + error (0, 0, + _("%s has appeared; following new file"), + quoteaf (pretty_name (f))); } else if (f->ino != new_stats.st_ino || f->dev != new_stats.st_dev) { + /* File has been replaced (e.g., via log rotation) -- + tail the new one. */ new_file = true; - if (f->fd == -1) - { - error (0, 0, - _("%s has appeared; following end of new file"), - quote (pretty_name (f))); - } - else - { - /* Close the old one. */ - close_fd (f->fd, pretty_name (f)); - - /* File has been replaced (e.g., via log rotation) -- - tail the new one. */ - error (0, 0, - _("%s has been replaced; following end of new file"), - quote (pretty_name (f))); - } + + error (0, 0, + _("%s has been replaced; following new file"), + quoteaf (pretty_name (f))); + + /* Close the old one. */ + close_fd (f->fd, pretty_name (f)); + } else { - if (f->fd == -1) - { - /* This happens when one iteration finds the file missing, - then the preceding <dev,inode> pair is reused as the - file is recreated. */ - new_file = true; - } - else - { - close_fd (fd, pretty_name (f)); - } + /* No changes detected, so close new fd. */ + close_fd (fd, pretty_name (f)); } + /* FIXME: When a log is rotated, daemons tend to log to the + old file descriptor until the new file is present and + the daemon is sent a signal. Therefore tail may miss entries + being written to the old file. Perhaps we should keep + the older file open and continue to monitor it until + data is written to a new file. */ if (new_file) { /* Start at the beginning of the file. */ @@ -949,20 +1066,36 @@ recheck (struct File_spec *f, bool blocking) } /* Return true if any of the N_FILES files in F are live, i.e., have - open file descriptors. */ + open file descriptors, or should be checked again (see --retry). + When following descriptors, checking should only continue when any + of the files is not yet ignored. */ static bool -any_live_files (const struct File_spec *f, int n_files) +any_live_files (const struct File_spec *f, size_t n_files) { - int i; + size_t i; + + if (reopen_inaccessible_files && follow_mode == Follow_name) + return true; /* continue following for -F option */ for (i = 0; i < n_files; i++) - if (0 <= f[i].fd) - return true; + { + if (0 <= f[i].fd) + { + return true; + } + else + { + if (reopen_inaccessible_files && follow_mode == Follow_descriptor) + if (! f[i].ignore) + return true; + } + } + return false; } -/* Tail NFILES files forever, or until killed. +/* Tail N_FILES files forever, or until killed. The pertinent information for each file is stored in an entry of F. Loop over each of them, doing an fstat to see if they have changed size, and an occasional open/fstat to see if any dev/ino pair has changed. @@ -970,214 +1103,690 @@ any_live_files (const struct File_spec *f, int n_files) while and try again. Continue until the user interrupts us. */ static void -tail_forever (struct File_spec *f, int nfiles, double sleep_interval) +tail_forever (struct File_spec *f, size_t n_files, 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; + && n_files == 1 && ! S_ISREG (f[0].mode)); + size_t last; bool writer_is_dead = false; - last = nfiles - 1; + last = n_files - 1; while (1) { - int i; + size_t i; bool any_input = false; - 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], blocking); - continue; - } - - fd = f[i].fd; - name = pretty_name (&f[i]); - mode = f[i].mode; - - if (f[i].blocking != blocking) - { - 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)) - { - /* Don't update f[i].blocking if fcntl fails. */ - if (S_ISREG (f[i].mode) && errno == EPERM) - { - /* This happens when using tail -f on a file with - the append-only attribute. */ - } - else - error (EXIT_FAILURE, errno, - _("%s: cannot change nonblocking mode"), name); - } - else - f[i].blocking = blocking; - } - - if (!f[i].blocking) - { - if (fstat (fd, &stats) != 0) - { - f[i].fd = -1; - f[i].errnum = errno; - error (0, errno, "%s", name); - continue; - } - - if (f[i].mode == stats.st_mode - && (! S_ISREG (stats.st_mode) || f[i].size == stats.st_size) - && timespec_cmp (f[i].mtime, get_stat_mtime (&stats)) == 0) - { - if ((max_n_unchanged_stats_between_opens - <= f[i].n_unchanged_stats++) - && follow_mode == Follow_name) - { - recheck (&f[i], 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 = get_stat_mtime (&stats); - 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; - } - } - - bytes_read = dump_remainder (name, fd, - (f[i].blocking - ? COPY_A_BUFFER : COPY_TO_EOF)); - any_input |= (bytes_read != 0); - f[i].size += bytes_read; - } - - if (! any_live_files (f, nfiles) && ! reopen_inaccessible_files) - { - error (0, 0, _("no files remaining")); - break; - } - - if ((!any_input | blocking) && fflush (stdout) != 0) - error (EXIT_FAILURE, errno, _("write error")); + for (i = 0; i < n_files; 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], blocking); + continue; + } + + fd = f[i].fd; + name = pretty_name (&f[i]); + mode = f[i].mode; + + if (f[i].blocking != blocking) + { + 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)) + { + /* Don't update f[i].blocking if fcntl fails. */ + if (S_ISREG (f[i].mode) && errno == EPERM) + { + /* This happens when using tail -f on a file with + the append-only attribute. */ + } + else + error (EXIT_FAILURE, errno, + _("%s: cannot change nonblocking mode"), + quotef (name)); + } + else + f[i].blocking = blocking; + } + + if (!f[i].blocking) + { + if (fstat (fd, &stats) != 0) + { + f[i].fd = -1; + f[i].errnum = errno; + error (0, errno, "%s", quotef (name)); + close (fd); /* ignore failure */ + continue; + } + + if (f[i].mode == stats.st_mode + && (! S_ISREG (stats.st_mode) || f[i].size == stats.st_size) + && timespec_cmp (f[i].mtime, get_stat_mtime (&stats)) == 0) + { + if ((max_n_unchanged_stats_between_opens + <= f[i].n_unchanged_stats++) + && follow_mode == Follow_name) + { + recheck (&f[i], 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 = get_stat_mtime (&stats); + f[i].mode = stats.st_mode; + + /* reset counter */ + f[i].n_unchanged_stats = 0; + + /* XXX: This is only a heuristic, as the file may have also + been truncated and written to if st_size >= size + (in which case we ignore new data <= size). */ + if (S_ISREG (mode) && stats.st_size < f[i].size) + { + error (0, 0, _("%s: file truncated"), quotef (name)); + /* Assume the file was truncated to 0, + and therefore output all "new" data. */ + xlseek (fd, 0, SEEK_SET, name); + f[i].size = 0; + } + + if (i != last) + { + if (print_headers) + write_header (name); + last = i; + } + } + + bytes_read = dump_remainder (name, fd, + (f[i].blocking + ? COPY_A_BUFFER : COPY_TO_EOF)); + any_input |= (bytes_read != 0); + f[i].size += bytes_read; + } + + if (! any_live_files (f, n_files)) + { + error (0, 0, _("no files remaining")); + break; + } + + 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; - - if (xnanosleep (sleep_interval)) - error (EXIT_FAILURE, errno, _("cannot read realtime clock")); - - /* Once the writer is dead, read the files once more to - avoid a race condition. */ - writer_is_dead = (pid != 0 - && kill (pid, 0) != 0 - /* Handle the case in which you cannot send a - signal to the writer, so kill fails and sets - errno to EPERM. */ - && errno != EPERM); - } + { + if (writer_is_dead) + break; + + /* Once the writer is dead, read the files once more to + avoid a race condition. */ + writer_is_dead = (pid != 0 + && kill (pid, 0) != 0 + /* Handle the case in which you cannot send a + signal to the writer, so kill fails and sets + errno to EPERM. */ + && errno != EPERM); + + if (!writer_is_dead && xnanosleep (sleep_interval)) + error (EXIT_FAILURE, errno, _("cannot read realtime clock")); + + } } } +#if HAVE_INOTIFY + +/* Return true if any of the N_FILES files in F is remote, i.e., has + an open file descriptor and is on a network file system. */ + +static bool +any_remote_file (const struct File_spec *f, size_t n_files) +{ + size_t i; + + for (i = 0; i < n_files; i++) + if (0 <= f[i].fd && f[i].remote) + return true; + return false; +} + +/* Return true if any of the N_FILES files in F is non remote, i.e., has + an open file descriptor and is not on a network file system. */ + +static bool +any_non_remote_file (const struct File_spec *f, size_t n_files) +{ + size_t i; + + for (i = 0; i < n_files; i++) + if (0 <= f[i].fd && ! f[i].remote) + return true; + return false; +} + +/* Return true if any of the N_FILES files in F is a symlink. + Note we don't worry about the edge case where "-" exists, + since that will have the same consequences for inotify, + which is the only context this function is currently used. */ + +static bool +any_symlinks (const struct File_spec *f, size_t n_files) +{ + size_t i; + + struct stat st; + for (i = 0; i < n_files; i++) + if (lstat (f[i].name, &st) == 0 && S_ISLNK (st.st_mode)) + return true; + return false; +} + +/* Return true if any of the N_FILES files in F represents + stdin and is tailable. */ + +static bool +tailable_stdin (const struct File_spec *f, size_t n_files) +{ + size_t i; + + for (i = 0; i < n_files; i++) + if (!f[i].ignore && STREQ (f[i].name, "-")) + return true; + return false; +} + +static size_t +wd_hasher (const void *entry, size_t tabsize) +{ + const struct File_spec *spec = entry; + return spec->wd % tabsize; +} + +static bool +wd_comparator (const void *e1, const void *e2) +{ + const struct File_spec *spec1 = e1; + const struct File_spec *spec2 = e2; + return spec1->wd == spec2->wd; +} + +/* Output (new) data for FSPEC->fd. */ +static void +check_fspec (struct File_spec *fspec, struct File_spec **prev_fspec) +{ + struct stat stats; + char const *name; + + if (fspec->fd == -1) + return; + + name = pretty_name (fspec); + + if (fstat (fspec->fd, &stats) != 0) + { + fspec->errnum = errno; + close_fd (fspec->fd, name); + fspec->fd = -1; + return; + } + + /* XXX: This is only a heuristic, as the file may have also + been truncated and written to if st_size >= size + (in which case we ignore new data <= size). + Though in the inotify case it's more likely we'll get + separate events for truncate() and write(). */ + if (S_ISREG (fspec->mode) && stats.st_size < fspec->size) + { + error (0, 0, _("%s: file truncated"), quotef (name)); + xlseek (fspec->fd, 0, SEEK_SET, name); + fspec->size = 0; + } + else if (S_ISREG (fspec->mode) && stats.st_size == fspec->size + && timespec_cmp (fspec->mtime, get_stat_mtime (&stats)) == 0) + return; + + if (fspec != *prev_fspec) + { + if (print_headers) + write_header (name); + *prev_fspec = fspec; + } + + uintmax_t bytes_read = dump_remainder (name, fspec->fd, COPY_TO_EOF); + fspec->size += bytes_read; + + if (fflush (stdout) != 0) + error (EXIT_FAILURE, errno, _("write error")); +} + +/* Attempt to tail N_FILES files forever, or until killed. + Check modifications using the inotify events system. + Return false on error, or true to revert to polling. */ +static bool +tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, + double sleep_interval) +{ +# if TAIL_TEST_SLEEP + /* Delay between open() and inotify_add_watch() + to help trigger different cases. */ + xnanosleep (1000000); +# endif + unsigned int max_realloc = 3; + + /* Map an inotify watch descriptor to the name of the file it's watching. */ + Hash_table *wd_to_name; + + bool found_watchable_file = false; + bool tailed_but_unwatchable = false; + bool found_unwatchable_dir = false; + bool no_inotify_resources = false; + bool writer_is_dead = false; + struct File_spec *prev_fspec; + size_t evlen = 0; + char *evbuf; + size_t evbuf_off = 0; + size_t len = 0; + + wd_to_name = hash_initialize (n_files, NULL, wd_hasher, wd_comparator, NULL); + if (! wd_to_name) + xalloc_die (); + + /* The events mask used with inotify on files (not directories). */ + uint32_t inotify_wd_mask = IN_MODIFY; + /* TODO: Perhaps monitor these events in Follow_descriptor mode also, + to tag reported file names with "deleted", "moved" etc. */ + if (follow_mode == Follow_name) + inotify_wd_mask |= (IN_ATTRIB | IN_DELETE_SELF | IN_MOVE_SELF); + + /* Add an inotify watch for each watched file. If -F is specified then watch + its parent directory too, in this way when they re-appear we can add them + again to the watch list. */ + size_t i; + for (i = 0; i < n_files; i++) + { + if (!f[i].ignore) + { + size_t fnlen = strlen (f[i].name); + if (evlen < fnlen) + evlen = fnlen; + + f[i].wd = -1; + + if (follow_mode == Follow_name) + { + size_t dirlen = dir_len (f[i].name); + char prev = f[i].name[dirlen]; + f[i].basename_start = last_component (f[i].name) - f[i].name; + + f[i].name[dirlen] = '\0'; + + /* It's fine to add the same directory more than once. + In that case the same watch descriptor is returned. */ + f[i].parent_wd = inotify_add_watch (wd, dirlen ? f[i].name : ".", + (IN_CREATE | IN_DELETE + | IN_MOVED_TO | IN_ATTRIB)); + + f[i].name[dirlen] = prev; + + if (f[i].parent_wd < 0) + { + if (errno != ENOSPC) /* suppress confusing error. */ + error (0, errno, _("cannot watch parent directory of %s"), + quoteaf (f[i].name)); + else + error (0, 0, _("inotify resources exhausted")); + found_unwatchable_dir = true; + /* We revert to polling below. Note invalid uses + of the inotify API will still be diagnosed. */ + break; + } + } + + f[i].wd = inotify_add_watch (wd, f[i].name, inotify_wd_mask); + + if (f[i].wd < 0) + { + if (f[i].fd != -1) /* already tailed. */ + tailed_but_unwatchable = true; + if (errno == ENOSPC || errno == ENOMEM) + { + no_inotify_resources = true; + error (0, 0, _("inotify resources exhausted")); + break; + } + else if (errno != f[i].errnum) + error (0, errno, _("cannot watch %s"), quoteaf (f[i].name)); + continue; + } + + if (hash_insert (wd_to_name, &(f[i])) == NULL) + xalloc_die (); + + found_watchable_file = true; + } + } + + /* Linux kernel 2.6.24 at least has a bug where eventually, ENOSPC is always + returned by inotify_add_watch. In any case we should revert to polling + when there are no inotify resources. Also a specified directory may not + be currently present or accessible, so revert to polling. Also an already + tailed but unwatchable due rename/unlink race, should also revert. */ + if (no_inotify_resources || found_unwatchable_dir + || (follow_mode == Follow_descriptor && tailed_but_unwatchable)) + { + hash_free (wd_to_name); + + errno = 0; + return true; + } + if (follow_mode == Follow_descriptor && !found_watchable_file) + return false; + + prev_fspec = &(f[n_files - 1]); + + /* Check files again. New files or data can be available since last time we + checked and before they are watched by inotify. */ + for (i = 0; i < n_files; i++) + { + if (! f[i].ignore) + { + /* check for new files. */ + if (follow_mode == Follow_name) + recheck (&(f[i]), false); + else if (f[i].fd != -1) + { + /* If the file was replaced in the small window since we tailed, + then assume the watch is on the wrong item (different to + that we've already produced output for), and so revert to + polling the original descriptor. */ + struct stat stats; + + if (stat (f[i].name, &stats) == 0 + && (f[i].dev != stats.st_dev || f[i].ino != stats.st_ino)) + { + error (0, errno, _("%s was replaced"), + quoteaf (pretty_name (&(f[i])))); + hash_free (wd_to_name); + + errno = 0; + return true; + } + } + + /* check for new data. */ + check_fspec (&f[i], &prev_fspec); + } + } + + evlen += sizeof (struct inotify_event) + 1; + evbuf = xmalloc (evlen); + + /* Wait for inotify events and handle them. Events on directories + ensure that watched files can be re-added when following by name. + This loop blocks on the 'safe_read' call until a new event is notified. + But when --pid=P is specified, tail usually waits via the select. */ + while (1) + { + struct File_spec *fspec; + struct inotify_event *ev; + void *void_ev; + + /* When following by name without --retry, and the last file has + been unlinked or renamed-away, diagnose it and return. */ + if (follow_mode == Follow_name + && ! reopen_inaccessible_files + && hash_get_n_entries (wd_to_name) == 0) + { + error (0, 0, _("no files remaining")); + return false; + } + + /* When watching a PID, ensure that a read from WD will not block + indefinitely. */ + if (pid) + { + if (writer_is_dead) + exit (EXIT_SUCCESS); + + writer_is_dead = (kill (pid, 0) != 0 && errno != EPERM); + + struct timeval delay; /* how long to wait for file changes. */ + if (writer_is_dead) + delay.tv_sec = delay.tv_usec = 0; + else + { + delay.tv_sec = (time_t) sleep_interval; + delay.tv_usec = 1000000 * (sleep_interval - delay.tv_sec); + } + + fd_set rfd; + FD_ZERO (&rfd); + FD_SET (wd, &rfd); + + int file_change = select (wd + 1, &rfd, NULL, NULL, &delay); + + if (file_change == 0) + continue; + else if (file_change == -1) + error (EXIT_FAILURE, errno, _("error monitoring inotify event")); + } + + if (len <= evbuf_off) + { + len = safe_read (wd, evbuf, evlen); + evbuf_off = 0; + + /* For kernels prior to 2.6.21, read returns 0 when the buffer + is too small. */ + if ((len == 0 || (len == SAFE_READ_ERROR && errno == EINVAL)) + && max_realloc--) + { + len = 0; + evlen *= 2; + evbuf = xrealloc (evbuf, evlen); + continue; + } + + if (len == 0 || len == SAFE_READ_ERROR) + error (EXIT_FAILURE, errno, _("error reading inotify event")); + } + + void_ev = evbuf + evbuf_off; + ev = void_ev; + evbuf_off += sizeof (*ev) + ev->len; + + if (ev->len) /* event on ev->name in watched directory. */ + { + size_t j; + for (j = 0; j < n_files; j++) + { + /* With N=hundreds of frequently-changing files, this O(N^2) + process might be a problem. FIXME: use a hash table? */ + if (f[j].parent_wd == ev->wd + && STREQ (ev->name, f[j].name + f[j].basename_start)) + break; + } + + /* It is not a watched file. */ + if (j == n_files) + continue; + + fspec = &(f[j]); + + int new_wd = -1; + bool deleting = !! (ev->mask & IN_DELETE); + + if (! deleting) + { + /* Adding the same inode again will look up any existing wd. */ + new_wd = inotify_add_watch (wd, f[j].name, inotify_wd_mask); + } + + if (! deleting && new_wd < 0) + { + if (errno == ENOSPC || errno == ENOMEM) + { + error (0, 0, _("inotify resources exhausted")); + hash_free (wd_to_name); + errno = 0; + return true; /* revert to polling. */ + } + else + { + /* Can get ENOENT for a dangling symlink for example. */ + error (0, errno, _("cannot watch %s"), quoteaf (f[j].name)); + } + /* We'll continue below after removing the existing watch. */ + } + + /* This will be false if only attributes of file change. */ + bool new_watch; + new_watch = (! deleting) && (fspec->wd < 0 || new_wd != fspec->wd); + + if (new_watch) + { + if (0 <= fspec->wd) + { + inotify_rm_watch (wd, fspec->wd); + hash_delete (wd_to_name, fspec); + } + + fspec->wd = new_wd; + + if (new_wd == -1) + continue; + + /* If the file was moved then inotify will use the source file wd + for the destination file. Make sure the key is not present in + the table. */ + struct File_spec *prev = hash_delete (wd_to_name, fspec); + if (prev && prev != fspec) + { + if (follow_mode == Follow_name) + recheck (prev, false); + prev->wd = -1; + close_fd (prev->fd, pretty_name (prev)); + } + + if (hash_insert (wd_to_name, fspec) == NULL) + xalloc_die (); + } + + if (follow_mode == Follow_name) + recheck (fspec, false); + } + else + { + struct File_spec key; + key.wd = ev->wd; + fspec = hash_lookup (wd_to_name, &key); + } + + if (! fspec) + continue; + + if (ev->mask & (IN_ATTRIB | IN_DELETE | IN_DELETE_SELF | IN_MOVE_SELF)) + { + /* Note for IN_MOVE_SELF (the file we're watching has + been clobbered via a rename) we leave the watch + in place since it may still be part of the set + of watched names. */ + if (ev->mask & IN_DELETE_SELF) + { + inotify_rm_watch (wd, fspec->wd); + hash_delete (wd_to_name, fspec); + } + + /* Note we get IN_ATTRIB for unlink() as st_nlink decrements. + The usual path is a close() done in recheck() triggers + an IN_DELETE_SELF event as the inode is removed. + However sometimes open() will succeed as even though + st_nlink is decremented, the dentry (cache) is not updated. + Thus we depend on the IN_DELETE event on the directory + to trigger processing for the removed file. */ + + recheck (fspec, false); + + continue; + } + check_fspec (fspec, &prev_fspec); + } +} +#endif + /* Output the last N_BYTES bytes of file FILENAME open for reading in FD. Return true if successful. */ static bool tail_bytes (const char *pretty_filename, int fd, uintmax_t n_bytes, - uintmax_t *read_pos) + uintmax_t *read_pos) { struct stat stats; if (fstat (fd, &stats)) { - error (0, errno, _("cannot fstat %s"), quote (pretty_filename)); + error (0, errno, _("cannot fstat %s"), quoteaf (pretty_filename)); return false; } if (from_start) { if ( ! presume_input_pipe - && S_ISREG (stats.st_mode) && n_bytes <= OFF_T_MAX) - { - xlseek (fd, n_bytes, SEEK_CUR, pretty_filename); - *read_pos += n_bytes; - } + && S_ISREG (stats.st_mode) && n_bytes <= OFF_T_MAX) + { + xlseek (fd, n_bytes, SEEK_CUR, pretty_filename); + *read_pos += n_bytes; + } else - { - int t = start_bytes (pretty_filename, fd, n_bytes, read_pos); - if (t) - return t < 0; - } - *read_pos += dump_remainder (pretty_filename, fd, COPY_TO_EOF); + { + int t = start_bytes (pretty_filename, fd, n_bytes, read_pos); + if (t) + return t < 0; + } + n_bytes = COPY_TO_EOF; } else { - if ( ! presume_input_pipe - && S_ISREG (stats.st_mode) && n_bytes <= OFF_T_MAX) - { - off_t current_pos = xlseek (fd, 0, SEEK_CUR, pretty_filename); - off_t end_pos = xlseek (fd, 0, SEEK_END, pretty_filename); - off_t diff = end_pos - current_pos; - /* Be careful here. The current position may actually be - beyond the end of the file. */ - off_t bytes_remaining = (diff = end_pos - current_pos) < 0 ? 0 : diff; - off_t nb = n_bytes; - - if (bytes_remaining <= nb) - { - /* From the current position to end of file, there are no - more bytes than have been requested. So reposition the - file pointer to the incoming current position and print - everything after that. */ - *read_pos = xlseek (fd, current_pos, SEEK_SET, pretty_filename); - } - else - { - /* There are more bytes remaining than were requested. - Back up. */ - *read_pos = xlseek (fd, -nb, SEEK_END, pretty_filename); - } - *read_pos += dump_remainder (pretty_filename, fd, n_bytes); - } - else - return pipe_bytes (pretty_filename, fd, n_bytes, read_pos); + off_t end_pos = ((! presume_input_pipe && usable_st_size (&stats) + && n_bytes <= OFF_T_MAX) + ? stats.st_size : -1); + if (end_pos <= ST_BLKSIZE (stats)) + return pipe_bytes (pretty_filename, fd, n_bytes, read_pos); + off_t current_pos = xlseek (fd, 0, SEEK_CUR, pretty_filename); + if (current_pos < end_pos) + { + off_t bytes_remaining = end_pos - current_pos; + + if (n_bytes < bytes_remaining) + { + current_pos = end_pos - n_bytes; + xlseek (fd, current_pos, SEEK_SET, pretty_filename); + } + } + *read_pos = current_pos; } + + *read_pos += dump_remainder (pretty_filename, fd, n_bytes); return true; } @@ -1186,13 +1795,13 @@ tail_bytes (const char *pretty_filename, int fd, uintmax_t n_bytes, static bool tail_lines (const char *pretty_filename, int fd, uintmax_t n_lines, - uintmax_t *read_pos) + uintmax_t *read_pos) { struct stat stats; if (fstat (fd, &stats)) { - error (0, errno, _("cannot fstat %s"), quote (pretty_filename)); + error (0, errno, _("cannot fstat %s"), quoteaf (pretty_filename)); return false; } @@ -1200,7 +1809,7 @@ tail_lines (const char *pretty_filename, int fd, uintmax_t n_lines, { int t = start_lines (pretty_filename, fd, n_lines, read_pos); if (t) - return t < 0; + return t < 0; *read_pos += dump_remainder (pretty_filename, fd, COPY_TO_EOF); } else @@ -1209,29 +1818,29 @@ tail_lines (const char *pretty_filename, int fd, uintmax_t n_lines, off_t end_pos; /* Use file_lines only if FD refers to a regular file for - which lseek (... SEEK_END) works. */ + which lseek (... SEEK_END) works. */ if ( ! presume_input_pipe - && S_ISREG (stats.st_mode) - && (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, - start_pos, end_pos, read_pos)) - return false; - } + && S_ISREG (stats.st_mode) + && (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, + start_pos, end_pos, read_pos)) + return false; + } else - { - /* Under very unlikely circumstances, it is possible to reach - this point after positioning the file pointer to end of file - via the `lseek (...SEEK_END)' above. In that case, reposition - the file pointer back to start_pos before calling pipe_lines. */ - if (start_pos != -1) - xlseek (fd, start_pos, SEEK_SET, pretty_filename); - - return pipe_lines (pretty_filename, fd, n_lines, read_pos); - } + { + /* Under very unlikely circumstances, it is possible to reach + this point after positioning the file pointer to end of file + via the 'lseek (...SEEK_END)' above. In that case, reposition + the file pointer back to start_pos before calling pipe_lines. */ + if (start_pos != -1) + xlseek (fd, start_pos, SEEK_SET, pretty_filename); + + return pipe_lines (pretty_filename, fd, n_lines, read_pos); + } } return true; } @@ -1273,7 +1882,7 @@ tail_file (struct File_spec *f, uintmax_t n_units) have_read_stdin = true; fd = STDIN_FILENO; if (O_BINARY && ! isatty (STDIN_FILENO)) - freopen (NULL, "rb", stdin); + xfreopen (NULL, "rb", stdin); } else fd = open (f->name, O_RDONLY | O_BINARY); @@ -1283,15 +1892,15 @@ tail_file (struct File_spec *f, uintmax_t n_units) if (fd == -1) { if (forever) - { - f->fd = -1; - f->errnum = errno; - f->ignore = false; - f->ino = 0; - f->dev = 0; - } + { + f->fd = -1; + f->errnum = errno; + f->ignore = false; + f->ino = 0; + f->dev = 0; + } error (0, errno, _("cannot open %s for reading"), - quote (pretty_name (f))); + quoteaf (pretty_name (f))); ok = false; } else @@ -1299,56 +1908,59 @@ tail_file (struct File_spec *f, uintmax_t n_units) uintmax_t read_pos; if (print_headers) - write_header (pretty_name (f)); + write_header (pretty_name (f)); ok = tail (pretty_name (f), fd, n_units, &read_pos); if (forever) - { - struct stat stats; - -#if TEST_RACE_BETWEEN_FINAL_READ_AND_INITIAL_FSTAT - /* Before the tail function provided `read_pos', there was - a race condition described in the URL below. This sleep - call made the window big enough to exercise the problem. */ - sleep (1); + { + struct stat stats; + +#if TAIL_TEST_SLEEP + /* Before the tail function provided 'read_pos', there was + a race condition described in the URL below. This sleep + call made the window big enough to exercise the problem. */ + xnanosleep (1); #endif - f->errnum = ok - 1; - if (fstat (fd, &stats) < 0) - { - ok = false; - f->errnum = errno; - error (0, errno, _("error reading %s"), quote (pretty_name (f))); - } - else if (!IS_TAILABLE_FILE_TYPE (stats.st_mode)) - { - error (0, 0, _("%s: cannot follow end of this type of file;\ + f->errnum = ok - 1; + if (fstat (fd, &stats) < 0) + { + ok = false; + f->errnum = errno; + error (0, errno, _("error reading %s"), + quoteaf (pretty_name (f))); + } + else if (!IS_TAILABLE_FILE_TYPE (stats.st_mode)) + { + error (0, 0, _("%s: cannot follow end of this type of file;\ giving up on this name"), - pretty_name (f)); - ok = false; - f->errnum = -1; - f->ignore = true; - } - - if (!ok) - { - close_fd (fd, pretty_name (f)); - f->fd = -1; - } - else - { - /* 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 */ - record_open_fd (f, fd, read_pos, &stats, (is_stdin ? -1 : 1)); - } - } + quotef (pretty_name (f))); + ok = false; + f->errnum = -1; + f->ignore = true; + } + + if (!ok) + { + close_fd (fd, pretty_name (f)); + f->fd = -1; + } + else + { + /* 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 */ + record_open_fd (f, fd, read_pos, &stats, (is_stdin ? -1 : 1)); + f->remote = fremote (fd, pretty_name (f)); + } + } else - { - if (!is_stdin && close (fd)) - { - error (0, errno, _("error reading %s"), quote (pretty_name (f))); - ok = false; - } - } + { + if (!is_stdin && close (fd)) + { + error (0, errno, _("error reading %s"), + quoteaf (pretty_name (f))); + ok = false; + } + } } return ok; @@ -1378,8 +1990,8 @@ parse_obsolete_option (int argc, char * const *argv, uintmax_t *n_units) /* With the obsolete form, there is one option string and at most one file argument. Watch out for "-" and "--", though. */ if (! (argc == 2 - || (argc == 3 && ! (argv[2][0] == '-' && argv[2][1])) - || (3 <= argc && argc <= 4 && STREQ (argv[2], "--")))) + || (argc == 3 && ! (argv[2][0] == '-' && argv[2][1])) + || (3 <= argc && argc <= 4 && STREQ (argv[2], "--")))) return false; obsolete_usage = (posix2_version () < 200112); @@ -1393,18 +2005,18 @@ parse_obsolete_option (int argc, char * const *argv, uintmax_t *n_units) case '+': /* Leading "+" is a file name in the non-obsolete form. */ if (!obsolete_usage) - return false; + return false; t_from_start = true; break; case '-': /* In the non-obsolete form, "-" is standard input and "-c" - requires an option-argument. The obsolete multidigit options - are supported as a GNU extension even when conforming to - POSIX 1003.1-2001, so don't complain about them. */ + requires an option-argument. The obsolete multidigit options + are supported as a GNU extension even when conforming to + POSIX 1003.1-2001, so don't complain about them. */ if (!obsolete_usage && !p[p[0] == 'c']) - return false; + return false; t_from_start = false; break; @@ -1434,9 +2046,12 @@ parse_obsolete_option (int argc, char * const *argv, uintmax_t *n_units) if (n_string == n_string_end) *n_units = default_count; else if ((xstrtoumax (n_string, NULL, 10, n_units, "b") - & ~LONGINT_INVALID_SUFFIX_CHAR) - != LONGINT_OK) - error (EXIT_FAILURE, 0, _("number in %s is too large"), quote (argv[1])); + & ~LONGINT_INVALID_SUFFIX_CHAR) + != LONGINT_OK) + { + error (EXIT_FAILURE, errno, "%s: %s", _("invalid number"), + quote (argv[1])); + } /* Set globals. */ from_start = t_from_start; @@ -1448,126 +2063,121 @@ parse_obsolete_option (int argc, char * const *argv, uintmax_t *n_units) static void parse_options (int argc, char **argv, - uintmax_t *n_units, enum header_mode *header_mode, - double *sleep_interval) + uintmax_t *n_units, enum header_mode *header_mode, + double *sleep_interval) { int c; - while ((c = getopt_long (argc, argv, "c:n:fFqs:v0123456789", - long_options, NULL)) - != -1) + while ((c = getopt_long (argc, argv, "c:n:fFqs:vz0123456789", + long_options, NULL)) + != -1) { switch (c) - { - case 'F': - forever = true; - follow_mode = Follow_name; - reopen_inaccessible_files = true; - break; - - case 'c': - case 'n': - count_lines = (c == 'n'); - if (*optarg == '+') - from_start = true; - else if (*optarg == '-') - ++optarg; - - { - strtol_error s_err; - s_err = xstrtoumax (optarg, NULL, 10, n_units, "bkm"); - if (s_err != LONGINT_OK) - { - error (EXIT_FAILURE, 0, "%s: %s", optarg, - (c == 'n' - ? _("invalid number of lines") - : _("invalid number of bytes"))); - } - } - break; - - case 'f': - case LONG_FOLLOW_OPTION: - forever = true; - if (optarg == NULL) - follow_mode = DEFAULT_FOLLOW_MODE; - else - follow_mode = XARGMATCH ("--follow", optarg, - follow_mode_string, follow_mode_map); - break; - - case RETRY_OPTION: - reopen_inaccessible_files = true; - break; - - case MAX_UNCHANGED_STATS_OPTION: - /* --max-unchanged-stats=N */ - if (xstrtoumax (optarg, NULL, 10, - &max_n_unchanged_stats_between_opens, - "") - != LONGINT_OK) - { - error (EXIT_FAILURE, 0, - _("%s: invalid maximum number of unchanged stats between opens"), - optarg); - } - break; - - case PID_OPTION: - { - strtol_error s_err; - unsigned long int tmp_ulong; - s_err = xstrtoul (optarg, NULL, 10, &tmp_ulong, ""); - if (s_err != LONGINT_OK || tmp_ulong > PID_T_MAX) - { - error (EXIT_FAILURE, 0, _("%s: invalid PID"), optarg); - } - pid = tmp_ulong; - } - break; - - case PRESUME_INPUT_PIPE_OPTION: - presume_input_pipe = true; - break; - - case 'q': - *header_mode = never; - break; - - case 's': - { - double s; - if (! (xstrtod (optarg, NULL, &s, c_strtod) && 0 <= s)) - error (EXIT_FAILURE, 0, - _("%s: invalid number of seconds"), optarg); - *sleep_interval = s; - } - break; - - case 'v': - *header_mode = always; - break; - - case_GETOPT_HELP_CHAR; - - case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS); - - case '0': case '1': case '2': case '3': case '4': - case '5': case '6': case '7': case '8': case '9': - error (EXIT_FAILURE, 0, - _("option used in invalid context -- %c"), c); - - default: - usage (EXIT_FAILURE); - } + { + case 'F': + forever = true; + follow_mode = Follow_name; + reopen_inaccessible_files = true; + break; + + case 'c': + case 'n': + count_lines = (c == 'n'); + if (*optarg == '+') + from_start = true; + else if (*optarg == '-') + ++optarg; + + *n_units = xdectoumax (optarg, 0, UINTMAX_MAX, "bkKmMGTPEZY0", + count_lines + ? _("invalid number of lines") + : _("invalid number of bytes"), 0); + break; + + case 'f': + case LONG_FOLLOW_OPTION: + forever = true; + if (optarg == NULL) + follow_mode = DEFAULT_FOLLOW_MODE; + else + follow_mode = XARGMATCH ("--follow", optarg, + follow_mode_string, follow_mode_map); + break; + + case RETRY_OPTION: + reopen_inaccessible_files = true; + break; + + case MAX_UNCHANGED_STATS_OPTION: + /* --max-unchanged-stats=N */ + max_n_unchanged_stats_between_opens = + xdectoumax (optarg, 0, UINTMAX_MAX, "", + _("invalid maximum number of unchanged stats between opens"), 0); + break; + + case DISABLE_INOTIFY_OPTION: + disable_inotify = true; + break; + + case PID_OPTION: + pid = xdectoumax (optarg, 0, PID_T_MAX, "", _("invalid PID"), 0); + break; + + case PRESUME_INPUT_PIPE_OPTION: + presume_input_pipe = true; + break; + + case 'q': + *header_mode = never; + break; + + case 's': + { + double s; + if (! (xstrtod (optarg, NULL, &s, c_strtod) && 0 <= s)) + error (EXIT_FAILURE, 0, + _("invalid number of seconds: %s"), quote (optarg)); + *sleep_interval = s; + } + break; + + case 'v': + *header_mode = always; + break; + + case 'z': + line_end = '\0'; + break; + + case_GETOPT_HELP_CHAR; + + case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS); + + case '0': case '1': case '2': case '3': case '4': + case '5': case '6': case '7': case '8': case '9': + error (EXIT_FAILURE, 0, + _("option used in invalid context -- %c"), c); + + default: + usage (EXIT_FAILURE); + } } - if (reopen_inaccessible_files && follow_mode != Follow_name) - error (0, 0, _("warning: --retry is useful mainly when following by name")); + if (reopen_inaccessible_files) + { + if (!forever) + { + reopen_inaccessible_files = false; + error (0, 0, _("warning: --retry ignored; --retry is useful" + " only when following")); + } + else if (follow_mode == Follow_descriptor) + error (0, 0, _("warning: --retry only effective for the initial open")); + } if (pid && !forever) error (0, 0, - _("warning: PID ignored; --pid=PID is useful only when following")); + _("warning: PID ignored; --pid=PID is useful only when following")); else if (pid && kill (pid, 0) != 0 && errno == ENOSYS) { error (0, 0, _("warning: --pid=PID is not supported on this system")); @@ -1575,6 +2185,35 @@ parse_options (int argc, char **argv, } } +/* Mark as '.ignore'd each member of F that corresponds to a + pipe or fifo, and return the number of non-ignored members. */ +static size_t +ignore_fifo_and_pipe (struct File_spec *f, size_t n_files) +{ + /* When there is no FILE operand and stdin is a pipe or FIFO + POSIX requires that tail ignore the -f option. + Since we allow multiple FILE operands, we extend that to say: with -f, + ignore any "-" operand that corresponds to a pipe or FIFO. */ + size_t n_viable = 0; + + size_t i; + for (i = 0; i < n_files; i++) + { + bool is_a_fifo_or_pipe = + (STREQ (f[i].name, "-") + && !f[i].ignore + && 0 <= f[i].fd + && (S_ISFIFO (f[i].mode) + || (HAVE_FIFO_PIPES != 1 && isapipe (f[i].fd)))); + if (is_a_fifo_or_pipe) + f[i].ignore = true; + else + ++n_viable; + } + + return n_viable; +} + int main (int argc, char **argv) { @@ -1584,10 +2223,10 @@ main (int argc, char **argv) the number of items at the end of the file to print. Although the type is signed, the value is never negative. */ uintmax_t n_units = DEFAULT_N_LINES; - int n_files; + size_t n_files; char **file; struct File_spec *F; - int i; + size_t i; bool obsolete_option; /* The number of seconds to sleep between iterations. @@ -1596,7 +2235,7 @@ main (int argc, char **argv) double sleep_interval = 1.0; initialize_main (&argc, &argv); - program_name = argv[0]; + set_program_name (argv[0]); setlocale (LC_ALL, ""); bindtextdomain (PACKAGE, LOCALEDIR); textdomain (PACKAGE); @@ -1607,20 +2246,23 @@ main (int argc, char **argv) count_lines = true; forever = from_start = print_headers = false; + line_end = '\n'; obsolete_option = parse_obsolete_option (argc, argv, &n_units); argc -= obsolete_option; argv += obsolete_option; parse_options (argc, argv, &n_units, &header_mode, &sleep_interval); /* To start printing with item N_UNITS from the start of the file, skip - N_UNITS - 1 items. `tail -n +0' is actually meaningless, but for Unix - compatibility it's treated the same as `tail -n +1'. */ + N_UNITS - 1 items. 'tail -n +0' is actually meaningless, but for Unix + compatibility it's treated the same as 'tail -n +1'. */ if (from_start) { if (n_units) - --n_units; + --n_units; } + IF_LINT (assert (0 <= argc)); + if (optind < argc) { n_files = argc - optind; @@ -1628,31 +2270,9 @@ main (int argc, char **argv) } else { - static char *dummy_stdin = "-"; + static char *dummy_stdin = (char *) "-"; n_files = 1; file = &dummy_stdin; - - /* POSIX says that -f is ignored if no file operand is specified - and standard input is a pipe. However, the GNU coding - standards say that program behavior should not depend on - device type, because device independence is an important - principle of the system's design. - - Follow the POSIX requirement only if POSIXLY_CORRECT is set. */ - - if (forever && getenv ("POSIXLY_CORRECT")) - { - struct stat st; - int is_a_fifo_or_pipe = - (fstat (STDIN_FILENO, &st) != 0 ? -1 - : S_ISFIFO (st.st_mode) ? 1 - : HAVE_FIFO_PIPES == 1 ? 0 - : isapipe (STDIN_FILENO)); - if (is_a_fifo_or_pipe < 0) - error (EXIT_FAILURE, errno, _("standard input")); - if (is_a_fifo_or_pipe) - forever = false; - } } { @@ -1660,20 +2280,24 @@ main (int argc, char **argv) for (i = 0; i < n_files; i++) if (STREQ (file[i], "-")) - found_hyphen = true; + found_hyphen = true; /* When following by name, there must be a name. */ if (found_hyphen && follow_mode == Follow_name) - error (EXIT_FAILURE, 0, _("cannot follow %s by name"), quote ("-")); + error (EXIT_FAILURE, 0, _("cannot follow %s by name"), quoteaf ("-")); - /* When following forever, warn if any file is `-'. + /* When following forever, warn if any file is '-'. This is only a warning, since tail's output (before a failing seek, and that from any non-stdin files) might still be useful. */ if (forever && found_hyphen && isatty (STDIN_FILENO)) error (0, 0, _("warning: following standard input" - " indefinitely is ineffective")); + " indefinitely is ineffective")); } + /* Don't read anything if we'll never output anything. */ + if (! n_units && ! forever && ! from_start) + return EXIT_SUCCESS; + F = xnmalloc (n_files, sizeof *F); for (i = 0; i < n_files; i++) F[i].name = file[i]; @@ -1683,15 +2307,99 @@ main (int argc, char **argv) print_headers = true; if (O_BINARY && ! isatty (STDOUT_FILENO)) - freopen (NULL, "wb", stdout); + xfreopen (NULL, "wb", stdout); for (i = 0; i < n_files; i++) ok &= tail_file (&F[i], n_units); - if (forever) - tail_forever (F, n_files, sleep_interval); + if (forever && ignore_fifo_and_pipe (F, n_files)) + { +#if HAVE_INOTIFY + /* tailable_stdin() checks if the user specifies stdin via "-", + or implicitly by providing no arguments. If so, we won't use inotify. + Technically, on systems with a working /dev/stdin, we *could*, + but would it be worth it? Verifying that it's a real device + and hooked up to stdin is not trivial, while reverting to + non-inotify-based tail_forever is easy and portable. + + any_remote_file() checks if the user has specified any + files that reside on remote file systems. inotify is not used + in this case because it would miss any updates to the file + that were not initiated from the local system. + + any_non_remote_file() checks if the user has specified any + files that don't reside on remote file systems. inotify is not used + if there are no open files, as we can't determine if those file + will be on a remote file system. + + any_symlinks() checks if the user has specified any symbolic links. + inotify is not used in this case because it returns updated _targets_ + which would not match the specified names. If we tried to always + use the target names, then we would miss changes to the symlink itself. + + ok is false when one of the files specified could not be opened for + reading. In this case and when following by descriptor, + tail_forever_inotify() cannot be used (in its current implementation). + + FIXME: inotify doesn't give any notification when a new + (remote) file or directory is mounted on top a watched file. + When follow_mode == Follow_name we would ideally like to detect that. + Note if there is a change to the original file then we'll + recheck it and follow the new file, or ignore it if the + file has changed to being remote. + + FIXME: when using inotify, and a directory for a watched file + is recreated, then we don't recheck any new file when + follow_mode == Follow_name. + + FIXME-maybe: inotify has a watch descriptor per inode, and hence with + our current hash implementation will only --follow data for one + of the names when multiple hardlinked files are specified, or + for one name when a name is specified multiple times. */ + if (!disable_inotify && (tailable_stdin (F, n_files) + || any_remote_file (F, n_files) + || ! any_non_remote_file (F, n_files) + || any_symlinks (F, n_files) + || (!ok && follow_mode == Follow_descriptor))) + disable_inotify = true; + + if (!disable_inotify) + { + int wd = inotify_init (); + if (0 <= wd) + { + /* Flush any output from tail_file, now, since + tail_forever_inotify flushes only after writing, + not before reading. */ + if (fflush (stdout) != 0) + error (EXIT_FAILURE, errno, _("write error")); + + if (! tail_forever_inotify (wd, F, n_files, sleep_interval)) + return EXIT_FAILURE; + } + error (0, errno, _("inotify cannot be used, reverting to polling")); + + /* Free resources as this process can be long lived, + and we may have exhausted system resources above. */ + + for (i = 0; i < n_files; i++) + { + /* It's OK to remove the same watch multiple times, + ignoring the EINVAL from redundant calls. */ + if (F[i].wd != -1) + inotify_rm_watch (wd, F[i].wd); + if (F[i].parent_wd != -1) + inotify_rm_watch (wd, F[i].parent_wd); + } + } +#endif + disable_inotify = true; + tail_forever (F, n_files, sleep_interval); + } + + IF_LINT (free (F)); if (have_read_stdin && close (STDIN_FILENO) < 0) error (EXIT_FAILURE, errno, "-"); - exit (ok ? EXIT_SUCCESS : EXIT_FAILURE); + return ok ? EXIT_SUCCESS : EXIT_FAILURE; } |