#!/usr/bin/env zsh
[ "${ZSH_VERSION:-}" = "" ] && echo >&2 "Only works with zsh" && exit 1
setopt err_exit no_unset pipefail extended_glob
# Simple script to update the godoc comments on all watchers so you don't need
# to update the same comment 5 times.
watcher=$(<<EOF
// Watcher watches a set of paths, delivering events on a channel.
//
// A watcher should not be copied (e.g. pass it by pointer, rather than by
// value).
//
// # Linux notes
//
// When a file is removed a Remove event won't be emitted until all file
// descriptors are closed, and deletes will always emit a Chmod. For example:
//
// fp := os.Open("file")
// os.Remove("file") // Triggers Chmod
// fp.Close() // Triggers Remove
//
// This is the event that inotify sends, so not much can be changed about this.
//
// The fs.inotify.max_user_watches sysctl variable specifies the upper limit
// for the number of watches per user, and fs.inotify.max_user_instances
// specifies the maximum number of inotify instances per user. Every Watcher you
// create is an "instance", and every path you add is a "watch".
//
// These are also exposed in /proc as /proc/sys/fs/inotify/max_user_watches and
// /proc/sys/fs/inotify/max_user_instances
//
// To increase them you can use sysctl or write the value to the /proc file:
//
// # Default values on Linux 5.18
// sysctl fs.inotify.max_user_watches=124983
// sysctl fs.inotify.max_user_instances=128
//
// To make the changes persist on reboot edit /etc/sysctl.conf or
// /usr/lib/sysctl.d/50-default.conf (details differ per Linux distro; check
// your distro's documentation):
//
// fs.inotify.max_user_watches=124983
// fs.inotify.max_user_instances=128
//
// Reaching the limit will result in a "no space left on device" or "too many open
// files" error.
//
// # kqueue notes (macOS, BSD)
//
// kqueue requires opening a file descriptor for every file that's being watched;
// so if you're watching a directory with five files then that's six file
// descriptors. You will run in to your system's "max open files" limit faster on
// these platforms.
//
// The sysctl variables kern.maxfiles and kern.maxfilesperproc can be used to
// control the maximum number of open files, as well as /etc/login.conf on BSD
// systems.
//
// # Windows notes
//
// Paths can be added as "C:\\path\\to\\dir", but forward slashes
// ("C:/path/to/dir") will also work.
//
// When a watched directory is removed it will always send an event for the
// directory itself, but may not send events for all files in that directory.
// Sometimes it will send events for all times, sometimes it will send no
// events, and often only for some files.
//
// The default ReadDirectoryChangesW() buffer size is 64K, which is the largest
// value that is guaranteed to work with SMB filesystems. If you have many
// events in quick succession this may not be enough, and you will have to use
// [WithBufferSize] to increase the value.
EOF
)
new=$(<<EOF
// NewWatcher creates a new Watcher.
EOF
)
newbuffered=$(<<EOF
// NewBufferedWatcher creates a new Watcher with a buffered Watcher.Events
// channel.
//
// The main use case for this is situations with a very large number of events
// where the kernel buffer size can't be increased (e.g. due to lack of
// permissions). An unbuffered Watcher will perform better for almost all use
// cases, and whenever possible you will be better off increasing the kernel
// buffers instead of adding a large userspace buffer.
EOF
)
add=$(<<EOF
// Add starts monitoring the path for changes.
//
// A path can only be watched once; watching it more than once is a no-op and will
// not return an error. Paths that do not yet exist on the filesystem cannot be
// watched.
//
// A watch will be automatically removed if the watched path is deleted or
// renamed. The exception is the Windows backend, which doesn't remove the
// watcher on renames.
//
// Notifications on network filesystems (NFS, SMB, FUSE, etc.) or special
// filesystems (/proc, /sys, etc.) generally don't work.
//
// Returns [ErrClosed] if [Watcher.Close] was called.
//
// See [Watcher.AddWith] for a version that allows adding options.
//
// # Watching directories
//
// All files in a directory are monitored, including new files that are created
// after the watcher is started. Subdirectories are not watched (i.e. it's
// non-recursive).
//
// # Watching files
//
// Watching individual files (rather than directories) is generally not
// recommended as many programs (especially editors) update files atomically: it
// will write to a temporary file which is then moved to to destination,
// overwriting the original (or some variant thereof). The watcher on the
// original file is now lost, as that no longer exists.
//
// The upshot of this is that a power failure or crash won't leave a
// half-written file.
//
// Watch the parent directory and use Event.Name to filter out files you're not
// interested in. There is an example of this in cmd/fsnotify/file.go.
EOF
)
addwith=$(<<EOF
// AddWith is like [Watcher.Add], but allows adding options. When using Add()
// the defaults described below are used.
//
// Possible options are:
//
// - [WithBufferSize] sets the buffer size for the Windows backend; no-op on
// other platforms. The default is 64K (65536 bytes).
EOF
)
remove=$(<<EOF
// Remove stops monitoring the path for changes.
//
// Directories are always removed non-recursively. For example, if you added
// /tmp/dir and /tmp/dir/subdir then you will need to remove both.
//
// Removing a path that has not yet been added returns [ErrNonExistentWatch].
//
// Returns nil if [Watcher.Close] was called.
EOF
)
close=$(<<EOF
// Close removes all watches and closes the Events channel.
EOF
)
watchlist=$(<<EOF
// WatchList returns all paths explicitly added with [Watcher.Add] (and are not
// yet removed).
//
// Returns nil if [Watcher.Close] was called.
EOF
)
events=$(<<EOF
// Events sends the filesystem change events.
//
// fsnotify can send the following events; a "path" here can refer to a
// file, directory, symbolic link, or special file like a FIFO.
//
// fsnotify.Create A new path was created; this may be followed by one
// or more Write events if data also gets written to a
// file.
//
// fsnotify.Remove A path was removed.
//
// fsnotify.Rename A path was renamed. A rename is always sent with the
// old path as Event.Name, and a Create event will be
// sent with the new name. Renames are only sent for
// paths that are currently watched; e.g. moving an
// unmonitored file into a monitored directory will
// show up as just a Create. Similarly, renaming a file
// to outside a monitored directory will show up as
// only a Rename.
//
// fsnotify.Write A file or named pipe was written to. A Truncate will
// also trigger a Write. A single "write action"
// initiated by the user may show up as one or multiple
// writes, depending on when the system syncs things to
// disk. For example when compiling a large Go program
// you may get hundreds of Write events, and you may
// want to wait until you've stopped receiving them
// (see the dedup example in cmd/fsnotify).
//
// Some systems may send Write event for directories
// when the directory content changes.
//
// fsnotify.Chmod Attributes were changed. On Linux this is also sent
// when a file is removed (or more accurately, when a
// link to an inode is removed). On kqueue it's sent
// when a file is truncated. On Windows it's never
// sent.
EOF
)
errors=$(<<EOF
// Errors sends any errors.
//
// ErrEventOverflow is used to indicate there are too many events:
//
// - inotify: There are too many queued events (fs.inotify.max_queued_events sysctl)
// - windows: The buffer size is too small; WithBufferSize() can be used to increase it.
// - kqueue, fen: Not used.
EOF
)
set-cmt() {
local pat=$1
local cmt=$2
IFS=$'\n' local files=($(grep -n $pat backend_*~*_test.go))
for f in $files; do
IFS=':' local fields=($=f)
local file=$fields[1]
local end=$(( $fields[2] - 1 ))
# Find start of comment.
local start=0
IFS=$'\n' local lines=($(head -n$end $file))
for (( i = 1; i <= $#lines; i++ )); do
local line=$lines[-$i]
if ! grep -q '^[[:space:]]*//' <<<$line; then
start=$(( end - (i - 2) ))
break
fi
done
head -n $(( start - 1 )) $file >/tmp/x
print -r -- $cmt >>/tmp/x
tail -n+$(( end + 1 )) $file >>/tmp/x
mv /tmp/x $file
done
}
set-cmt '^type Watcher struct ' $watcher
set-cmt '^func NewWatcher(' $new
set-cmt '^func NewBufferedWatcher(' $newbuffered
set-cmt '^func (w \*Watcher) Add(' $add
set-cmt '^func (w \*Watcher) AddWith(' $addwith
set-cmt '^func (w \*Watcher) Remove(' $remove
set-cmt '^func (w \*Watcher) Close(' $close
set-cmt '^func (w \*Watcher) WatchList(' $watchlist
set-cmt '^[[:space:]]*Events *chan Event$' $events
set-cmt '^[[:space:]]*Errors *chan error$' $errors
Codebase Browser
kubernetes