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fanotify.7: Minor wording and formatting fixes
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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Michael Kerrisk
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@ -36,7 +36,9 @@ for details of an API that does notify those events.)
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Additional capabilities compared to the
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.BR inotify (7)
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API are monitoring of complete mounts, access permission decisions, and the
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API include the ability to monitor all of the objects
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in a mounted filesystem,
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the ability to make access permission decisions, and the
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possibility to read or modify files before access by other applications.
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The following system calls are used with this API:
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@ -103,11 +105,14 @@ returned by
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.BR fanotify_init (2).
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Two types of events are generated:
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notification events and permission events.
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.I notification
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events and
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.I permission
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events.
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Notification events are merely informative
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and require no action to be taken by
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the receiving application except for closing the file descriptor passed
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in the event.
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in the event (see below).
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Permission events are requests to the receiving application to decide
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whether permission for a file access shall be granted.
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For these events, the recipient must write a response which decides whether
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@ -153,7 +158,9 @@ struct fanotify_event_metadata {
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.fi
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.in
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.PP
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The fields of this structure as follows:
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The fields of the
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.I fanotify_event_metadata
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structure are as follows:
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.TP
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.I event_len
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This is the length of the data for the current event and the offset
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@ -186,7 +193,7 @@ optional headers per event type.
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No such optional headers exist in the current implementation.
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.TP
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.I mask
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This is a bit mask describing the event.
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This is a bit mask describing the event (see below).
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.TP
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.I fd
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This is an open file descriptor for the object being accessed, or
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@ -194,13 +201,15 @@ This is an open file descriptor for the object being accessed, or
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if a queue overflow occurred.
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The file descriptor can be used to access the contents
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of the monitored file or directory.
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The reading application is responsible for closing this file descriptor.
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.IP
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The
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.B FMODE_NONOTIFY
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file status flag is set on the corresponding open file description.
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file status flag is set on the open file description
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that corresponds to this file descriptor.
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This flag suppresses fanotify event generation.
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Hence, when the receiver of the fanotify event accesses the notified file or
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directory using this file descriptor, no additional events will be created.
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The reading application is responsible for closing the file descriptor.
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.TP
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.I pid
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This is the ID of the process that caused the event.
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@ -208,11 +217,11 @@ A program listening to fanotify events can compare this PID
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to the PID returned by
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.BR getpid (2),
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to determine whether the event is caused by the listener itself,
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or is due to a file access by another program.
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or is due to a file access by another process.
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.PP
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The bit mask in
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.I mask
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signals which events have occurred for a single filesystem object.
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indicates which events have occurred for a single filesystem object.
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Multiple bits may be set in this mask,
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if more than one event occurred for the monitored filesystem object.
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In particular,
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@ -247,17 +256,18 @@ was closed.
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.TP
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.B FAN_Q_OVERFLOW
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The event queue exceeded the limit of 16384 entries.
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This limit can be overridden in the call to
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.BR fanotify_init (2)
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by setting the flag
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.BR FAN_UNLIMITED_QUEUE .
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This limit can be overridden by specifying the
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.BR FAN_UNLIMITED_QUEUE
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flag when calling
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.BR fanotify_init (2).
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.TP
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.B FAN_ACCESS_PERM
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An application wants to read a file or directory, for example using
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.BR read (2)
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or
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.BR readdir (2).
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The reader must write a response that determines whether the permission to
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The reader must write a response (as described below)
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that determines whether the permission to
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access the filesystem object shall be granted.
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.TP
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.B FAN_OPEN_PERM
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@ -269,14 +279,14 @@ To check for any close event, the following bit mask may be used:
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.TP
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.B FAN_CLOSE
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A file was closed.
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This is a synonym for;
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This is a synonym for:
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FAN_CLOSE_WRITE | FAN_CLOSE_NOWRITE
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.PP
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The following macros are provided to iterate over a buffer containing
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fanotify event metadata returned by a
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fanotify event metadata returned by a
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.BR read (2)
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from an fanotify file descriptor.
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from an fanotify file descriptor:
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.TP
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.B FAN_EVENT_OK(meta, len)
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This macro checks the remaining length
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@ -359,7 +369,7 @@ the following errors can occur when reading from the
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fanotify file descriptor:
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.TP
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.B EINVAL
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The buffer is too short to hold the event.
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The buffer is too small to hold the event.
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.TP
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.B EMFILE
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The per-process limit on the number of open files has been reached.
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@ -459,7 +469,7 @@ This poses a security risk, when the
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capability is set for programs executed by unprivileged users.
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.SH EXAMPLE
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The following program demonstrates the usage of the fanotify API.
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It marks the mount point passed as command-line argument
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It marks the mount point passed as a command-line argument
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and waits for events of type
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.B FAN_PERM_OPEN
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and
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