(Based on someone else's patch.)
Implementing -F with inotify is a lot more work (including more
portability shims for macOS), so this is a simpler polling
implementation.
Also fix my earlier mistake where xnotify_add() wasn't actually an 'x'
function that exits on failure.
---
lib/portability.c | 4 +-
toys/posix/tail.c | 117 +++++++++++++++++++++++++++++++++++++---------
2 files changed, 96 insertions(+), 25 deletions(-)
From 6940bc5d5c93e039ae66538d403ebdd5010b36aa Mon Sep 17 00:00:00 2001
From: Elliott Hughes <e...@google.com>
Date: Wed, 30 Jun 2021 16:38:42 -0700
Subject: [PATCH] tail: implement -F (and its companion -s).
(Based on someone else's patch.)
Implementing -F with inotify is a lot more work (including more
portability shims for macOS), so this is a simpler polling
implementation.
Also fix my earlier mistake where xnotify_add() wasn't actually an 'x'
function that exits on failure.
---
lib/portability.c | 4 +-
toys/posix/tail.c | 117 +++++++++++++++++++++++++++++++++++++---------
2 files changed, 96 insertions(+), 25 deletions(-)
diff --git a/lib/portability.c b/lib/portability.c
index 6118d0f2..f97af60e 100644
--- a/lib/portability.c
+++ b/lib/portability.c
@@ -211,7 +211,7 @@ int xnotify_add(struct xnotify *not, int fd, char *path)
if (not->count == not->max) error_exit("xnotify_add overflow");
EV_SET(&event, fd, EVFILT_VNODE, EV_ADD|EV_CLEAR, NOTE_WRITE, 0, NULL);
if (kevent(not->kq, &event, 1, NULL, 0, NULL) == -1 || event.flags & EV_ERROR)
- return -1;
+ error_exit("xnotify_add failed on %s", path);
not->paths[not->count] = path;
not->fds[not->count++] = fd;
@@ -257,7 +257,7 @@ int xnotify_add(struct xnotify *not, int fd, char *path)
if (not->max == not->count) error_exit("xnotify_add overflow");
if ((not->fds[i] = inotify_add_watch(not->kq, path, IN_MODIFY))==-1)
- return -1;
+ perror_exit("xnotify_add failed on %s", path);
not->fds[i+1] = fd;
not->paths[not->count++] = path;
diff --git a/toys/posix/tail.c b/toys/posix/tail.c
index 89ec70e8..842814c0 100644
--- a/toys/posix/tail.c
+++ b/toys/posix/tail.c
@@ -6,30 +6,39 @@
*
* Deviations from posix: -f waits for pipe/fifo on stdin (nonblock?).
-USE_TAIL(NEWTOY(tail, "?fc-n-[-cn]", TOYFLAG_USR|TOYFLAG_BIN))
+USE_TAIL(NEWTOY(tail, "?fFs#=1c-n-[-cn][-fF]", TOYFLAG_USR|TOYFLAG_BIN))
config TAIL
bool "tail"
default y
help
- usage: tail [-n|c NUMBER] [-f] [FILE...]
+ usage: tail [-n|c NUMBER] [-f|F] [-s SECONDS] [FILE...]
Copy last lines from files to stdout. If no files listed, copy from
stdin. Filename "-" is a synonym for stdin.
-n Output the last NUMBER lines (default 10), +X counts from start
-c Output the last NUMBER bytes, +NUMBER counts from start
- -f Follow FILE(s), waiting for more data to be appended
+ -f Follow FILE(s) by descriptor, waiting for more data to be appended
+ -F Follow FILE(s) by filename, waiting for more data, and retrying
+ -s Used with -F, sleep SECONDS between retries (default 1)
*/
#define FOR_tail
#include "toys.h"
-GLOBALS(
- long n, c;
+struct follow_file {
+ char *path;
+ int fd;
+ dev_t dev;
+ ino_t ino;
+};
+GLOBALS(
+ long n, c, s;
int file_no, last_fd;
struct xnotify *not;
+ struct follow_file *F;
)
struct line_list {
@@ -123,17 +132,89 @@ static int try_lseek(int fd, long bytes, long lines)
return 1;
}
+static void show_new(int fd, char *path)
+{
+ int len;
+
+ while ((len = read(fd, toybuf, sizeof(toybuf)))>0) {
+ if (TT.last_fd != fd) {
+ TT.last_fd = fd;
+ xprintf("\n==> %s <==\n", path);
+ }
+ xwrite(1, toybuf, len);
+ }
+}
+
+static void tail_F()
+{
+ struct stat sb;
+ int i, old_fd;
+
+ for (;;) {
+ for (i = 0; i<TT.file_no; ++i) {
+ old_fd = TT.F[i].fd;
+ if (stat(TT.F[i].path, &sb) != 0) {
+ if (old_fd >= 0) {
+ xprintf("tail: file inaccessible: %s\n", TT.F[i].path);
+ close(old_fd);
+ TT.F[i].fd = -1;
+ }
+ continue;
+ }
+
+ if (old_fd < 0 || sb.st_dev != TT.F[i].dev || sb.st_ino != TT.F[i].ino) {
+ if (old_fd >= 0) close(old_fd);
+ TT.F[i].fd = open(TT.F[i].path, O_RDONLY);
+ if (TT.F[i].fd == -1) continue;
+ else {
+ xprintf("tail: following new file: %s\n", TT.F[i].path);
+ TT.F[i].dev = sb.st_dev;
+ TT.F[i].ino = sb.st_ino;
+ }
+ } else if (sb.st_size && sb.st_size < lseek(TT.F[i].fd, 0, SEEK_CUR)) {
+ // If file was truncated, move to start.
+ xprintf("tail: file truncated: %s\n", TT.F[i].path);
+ xlseek(TT.F[i].fd, 0, SEEK_SET);
+ }
+
+ show_new(TT.F[i].fd, TT.F[i].path);
+ }
+
+ sleep(TT.s);
+ }
+}
+
+static void tail_f()
+{
+ char *path;
+ int fd;
+
+ for (;;) {
+ fd = xnotify_wait(TT.not, &path);
+ show_new(fd, path);
+ }
+}
+
// Called for each file listed on command line, and/or stdin
static void do_tail(int fd, char *name)
{
long bytes = TT.c, lines = TT.n;
int linepop = 1;
- if (FLAG(f)) {
+ if (FLAG(f) || FLAG(F)) {
char *s = name;
+ struct stat sb;
if (!fd) sprintf(s = toybuf, "/proc/self/fd/%d", fd);
- if (xnotify_add(TT.not, fd, s)) perror_exit("-f on '%s' failed", s);
+
+ if (FLAG(f)) xnotify_add(TT.not, fd, s);
+ if (FLAG(F)) {
+ if (fstat(fd, &sb) != 0) perror_exit("%s", name);
+ TT.F[TT.file_no].fd = fd;
+ TT.F[TT.file_no].path = s;
+ TT.F[TT.file_no].dev = sb.st_dev;
+ TT.F[TT.file_no].ino = sb.st_ino;
+ }
}
if (TT.file_no++) xputc('\n');
@@ -227,23 +308,13 @@ void tail_main(void)
}
}
- if (FLAG(f)) TT.not = xnotify_init(toys.optc);
- loopfiles_rw(args, O_RDONLY|WARN_ONLY|(O_CLOEXEC*!FLAG(f)), 0, do_tail);
+ if (FLAG(F)) TT.F = xmalloc(toys.optc * sizeof(struct follow_file));
+ else if (FLAG(f)) TT.not = xnotify_init(toys.optc);
- if (FLAG(f) && TT.file_no) {
- for (;;) {
- char *path;
- int fd = xnotify_wait(TT.not, &path), len;
-
- // Read new data.
- while ((len = read(fd, toybuf, sizeof(toybuf)))>0) {
- if (TT.last_fd != fd) {
- TT.last_fd = fd;
- xprintf("\n==> %s <==\n", path);
- }
+ loopfiles_rw(args, O_RDONLY|WARN_ONLY|(O_CLOEXEC*!(FLAG(f) || FLAG(F))), 0, do_tail);
- xwrite(1, toybuf, len);
- }
- }
+ if (TT.file_no) {
+ if (FLAG(F)) tail_F();
+ else if (FLAG(f)) tail_f();
}
}
--
2.32.0.93.g670b81a890-goog
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