diff options
Diffstat (limited to 'src/tail.c')
| -rw-r--r-- | src/tail.c | 148 |
1 files changed, 115 insertions, 33 deletions
@@ -1,5 +1,5 @@ /* tail -- output the last part of file(s) - Copyright (C) 1989-2013 Free Software Foundation, Inc. + Copyright (C) 1989-2014 Free Software Foundation, Inc. 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 @@ -268,25 +268,24 @@ With no FILE, or when FILE is -, read standard input.\n\ emit_mandatory_arg_note (); fputs (_("\ - -c, --bytes=K output the last K bytes; alternatively, use -c +K\n\ - to output bytes starting with the Kth of each file\n\ + -c, --bytes=K output the last K bytes; or use -c +K to output\n\ + bytes starting with the Kth 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=K output the last K lines, instead of the last %d;\n\ - or use -n +K to output lines starting with the Kth\n\ + or use -n +K to output starting with the Kth\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\ - With inotify, this option is rarely useful.\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 @@ -294,15 +293,13 @@ With no FILE, or when FILE is -, read standard input.\n\ fputs (_("\ --pid=PID with -f, terminate after process ID, PID dies\n\ -q, --quiet, --silent never output headers giving file names\n\ - --retry keep trying to open a file even when it is or\n\ - becomes inaccessible; useful when following by\n\ - name, i.e., with --follow=name\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\ + (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 (HELP_OPTION_DESCRIPTION, stdout); @@ -342,13 +339,6 @@ 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")); -} - /* Record a file F with descriptor FD, size SIZE, status ST, and blocking status BLOCKING. */ @@ -388,6 +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"), + quote ("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. @@ -948,7 +952,20 @@ 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"), quote (pretty_name (f))); + } + else if (fd == -1 || fstat (fd, &new_stats) < 0) { ok = false; f->errnum = errno; @@ -1054,16 +1071,32 @@ 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, size_t n_files) { 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; } @@ -1191,7 +1224,7 @@ tail_forever (struct File_spec *f, size_t n_files, double sleep_interval) f[i].size += bytes_read; } - if (! any_live_files (f, n_files) && ! reopen_inaccessible_files) + if (! any_live_files (f, n_files)) { error (0, 0, _("no files remaining")); break; @@ -1238,6 +1271,23 @@ any_remote_file (const struct File_spec *f, size_t n_files) 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. */ @@ -1272,7 +1322,12 @@ static void check_fspec (struct File_spec *fspec, int wd, int *prev_wd) { struct stat stats; - char const *name = pretty_name (fspec); + char const *name; + + if (fspec->fd == -1) + return; + + name = pretty_name (fspec); if (fstat (fspec->fd, &stats) != 0) { @@ -1432,6 +1487,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, { 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. */ @@ -1493,7 +1549,8 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, error (EXIT_FAILURE, errno, _("error reading inotify event")); } - ev = (struct inotify_event *) (evbuf + evbuf_off); + void_ev = evbuf + evbuf_off; + ev = void_ev; evbuf_off += sizeof (*ev) + ev->len; if (ev->len) /* event on ev->name in watched directory */ @@ -1516,6 +1573,7 @@ tail_forever_inotify (int wd, struct File_spec *f, size_t n_files, int new_wd = inotify_add_watch (wd, f[j].name, inotify_wd_mask); if (new_wd < 0) { + /* Can get ENOENT for a dangling symlink for example. */ error (0, errno, _("cannot watch %s"), quote (f[j].name)); continue; } @@ -2030,8 +2088,17 @@ parse_options (int argc, char **argv, } } - 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, @@ -2149,6 +2216,10 @@ main (int argc, char **argv) " indefinitely is ineffective")); } + /* Don't read anything if we'll never output anything. */ + if (! n_units && ! forever && ! from_start) + exit (EXIT_SUCCESS); + F = xnmalloc (n_files, sizeof *F); for (i = 0; i < n_files; i++) F[i].name = file[i]; @@ -2178,6 +2249,15 @@ main (int argc, char **argv) in this case because it would miss any updates to the file that were not initiated from the local 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. @@ -2189,7 +2269,9 @@ main (int argc, char **argv) is recreated, then we don't recheck any new file when follow_mode == Follow_name */ if (!disable_inotify && (tailable_stdin (F, n_files) - || any_remote_file (F, n_files))) + || any_remote_file (F, n_files) + || any_symlinks (F, n_files) + || (!ok && follow_mode == Follow_descriptor))) disable_inotify = true; if (!disable_inotify) |