.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
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-.TH FANOTIFY_INIT 2 2014-04-24 "Linux" "Linux Programmer's Manual"
+.TH FANOTIFY_INIT 2 2019-08-02 "Linux" "Linux Programmer's Manual"
.SH NAME
fanotify_init \- create and initialize fanotify group
.SH SYNOPSIS
.B #include <fcntl.h>
.br
.B #include <sys/fanotify.h>
-.sp
+.PP
.BI "int fanotify_init(unsigned int " flags ", unsigned int " event_f_flags );
.SH DESCRIPTION
For an overview of the fanotify API, see
.PP
The file descriptor is used in calls to
.BR fanotify_mark (2)
-to specify the files, directories, and mounts for which fanotify events shall
-be created.
+to specify the files, directories, mounts or filesystems for which fanotify
+events shall be created.
These events are received by reading from the file descriptor.
Some events are only informative, indicating that a file has been accessed.
Other events can be used to determine whether
The
.I flags
argument contains a multi-bit field defining the notification class of the
-listening application and further single bit fields specifying the behavior of
-the file descriptor.
+listening application and further single bit fields specifying the behavior
+of the file descriptor.
.PP
-If multiple listeners for permission events exist, the notification class is
-used to establish the sequence in which the listeners receive the events.
+If multiple listeners for permission events exist,
+the notification class is used to establish the sequence
+in which the listeners receive the events.
.PP
Only one of the following notification classes may be specified in
.IR flags :
accessed and events for permission decisions if a file may be accessed.
It is intended for event listeners that need to access files before they
contain their final data.
-This notification class might be used by hierarchical storage managers, for
-example.
+This notification class might be used by hierarchical storage managers,
+for example.
.TP
.B FAN_CLASS_CONTENT
This value allows the receipt of events notifying that a file has been
accessed and events for permission decisions if a file may be accessed.
-It is intended for event listeners that need to access files when they already
-contain their final content.
+It is intended for event listeners that need to access files when they
+already contain their final content.
This notification class might be used by malware detection programs, for
example.
.TP
+.BR FAN_REPORT_FID " (since Linux 5.1)"
+.\" commit a8b13aa20afb69161b5123b4f1acc7ea0a03d360
+This value allows the receipt of events which contain additional information
+about the underlying filesystem object correlated to an event.
+An additional structure encapsulates the information about the object and is
+included alongside the generic event metadata structure.
+The file descriptor that is used to represent the object correlated to an
+event is instead substituted with a file handle.
+It is intended for applications that may find the use of a file handle to
+identify an object more suitable than a file descriptor.
+Additionally, it may be used for applications that are interested in
+directory entry events, such as
+.BR FAN_CREATE ,
+.BR FAN_ATTRIB ,
+.BR FAN_MOVE ,
+and
+.BR FAN_DELETE
+for example.
+Note that the use of directory modification events are not supported when
+monitoring a mount point.
+The use of
+.BR FAN_CLASS_CONTENT
+or
+.BR FAN_CLASS_PRE_CONTENT
+is not permitted with this flag and will result in the error
+.BR EINVAL .
+See
+.BR fanotify (7)
+for additional information.
+.TP
.B FAN_CLASS_NOTIF
This is the default value.
It does not need to be specified.
.BR FAN_CLASS_PRE_CONTENT ,
.BR FAN_CLASS_CONTENT ,
.BR FAN_CLASS_NOTIF .
-The order of notification for listeners of the same value is undefined.
+The order of notification for listeners in the same notification class
+is undefined.
.PP
-The following bit mask values can be set additionally in
+The following bits can additionally be set in
.IR flags :
.TP
.B FAN_CLOEXEC
-This flag sets the close-on-exec flag
+Set the close-on-exec flag
.RB ( FD_CLOEXEC )
on the new file descriptor.
See the description of the
.BR open (2).
.TP
.B FAN_NONBLOCK
-This flag enables the nonblocking flag
+Enable the nonblocking flag
.RB ( O_NONBLOCK )
for the file descriptor.
Reading from the file descriptor will not block.
Instead, if no data is available,
.BR read (2)
-will fail with the error
+fails with the error
.BR EAGAIN .
.TP
.B FAN_UNLIMITED_QUEUE
-This flag removes the limit of 16384 events for the event queue.
-It requires the
+Remove the limit of 16384 events for the event queue.
+Use of this flag requires the
.B CAP_SYS_ADMIN
capability.
.TP
.B FAN_UNLIMITED_MARKS
-This flag removes the limit of 8192 marks.
-It requires the
+Remove the limit of 8192 marks.
+Use of this flag requires the
.B CAP_SYS_ADMIN
capability.
+.TP
+.BR FAN_REPORT_TID " (since Linux 4.20)"
+.\" commit d0a6a87e40da49cfc7954c491d3065a25a641b29
+Report thread ID (TID) instead of process ID (PID)
+in the
+.I pid
+field of the
+.I "struct fanotify_event_metadata"
+supplied to
+.BR read (2)
+(see
+.BR fanotify (7)).
.PP
-The argument
+The
.I event_f_flags
-defines the file flags with which file descriptors for fanotify events shall
-be created.
-For explanations of possible values, see the argument
+argument
+defines the file status flags that will be set on the open file descriptions
+that are created for fanotify events.
+For details of these flags, see the description of the
.I flags
-of the
-.BR open (2)
-system call.
-Useful values are:
+values in
+.BR open (2).
+.I event_f_flags
+includes a multi-bit field for the access mode.
+This field can take the following values:
.TP
.B O_RDONLY
This value allows only read access.
.TP
.B O_RDWR
This value allows read and write access.
-.TP
-.B O_CLOEXEC
-This flag enables the close-on-exec flag for the file descriptor.
+.PP
+Additional bits can be set in
+.IR event_f_flags .
+The most useful values are:
.TP
.B O_LARGEFILE
-This flag enables support for files exceeding 2 GB.
+Enable support for files exceeding 2\ GB.
Failing to set this flag will result in an
.B EOVERFLOW
-error when trying to open a large file which is monitored by an fanotify group
-on a 32-bit system.
+error when trying to open a large file which is monitored by
+an fanotify group on a 32-bit system.
+.TP
+.BR O_CLOEXEC " (since Linux 3.18)"
+.\" commit 0b37e097a648aa71d4db1ad108001e95b69a2da4
+Enable the close-on-exec flag for the file descriptor.
+See the description of the
+.B O_CLOEXEC
+flag in
+.BR open (2)
+for reasons why this may be useful.
+.PP
+The following are also allowable:
+.BR O_APPEND ,
+.BR O_DSYNC ,
+.BR O_NOATIME ,
+.BR O_NONBLOCK ,
+and
+.BR O_SYNC .
+Specifying any other flag in
+.I event_f_flags
+yields the error
+.B EINVAL
+(but see BUGS).
.SH RETURN VALUE
On success,
.BR fanotify_init ()
.TP
.B EINVAL
An invalid value was passed in
-.IR flags .
+.I flags
+or
+.IR event_f_flags .
.B FAN_ALL_INIT_FLAGS
-defines all allowable bits.
+(deprecated since Linux kernel version 4.20)
+.\" commit 23c9deeb3285d34fd243abb3d6b9f07db60c3cf4
+defines all allowable bits for
+.IR flags .
+.TP
+.B EMFILE
+The number of fanotify groups for this user exceeds 128.
.TP
.B EMFILE
-The number of fanotify groups of the user exceeds 128.
+The per-process limit on the number of open file descriptors has been reached.
.TP
.B ENOMEM
The allocation of memory for the notification group failed.
.B ENOSYS
This kernel does not implement
.BR fanotify_init ().
-To make the fanotify API available,
-.B CONFIG_FANOTIFY
-has to be enabled in the Linux configuration.
+The fanotify API is available only if the kernel was configured with
+.BR CONFIG_FANOTIFY .
.TP
.B EPERM
The operation is not permitted because the caller lacks the
.BR fanotify_init ()
was introduced in version 2.6.36 of the Linux kernel and enabled in version
2.6.37.
-.SH "CONFORMING TO"
+.SH CONFORMING TO
This system call is Linux-specific.
.SH BUGS
-As of Linux 3.15,
-the following bug exists:
+The following bug was present in Linux kernels before version 3.18:
+.IP * 3
+.\" Fixed by commit 0b37e097a648aa71d4db1ad108001e95b69a2da4
+The
+.B O_CLOEXEC
+is ignored when passed in
+.IR event_f_flags .
+.PP
+The following bug was present in Linux kernels before version 3.14:
.IP * 3
-.\" FIXME: Patch proposed.
+.\" Fixed by commit 48149e9d3a7e924010a0daab30a6197b7d7b6580
The
.I event_f_flags
-argument is not checked is not checked for invalid flags.
+argument is not checked for invalid flags.
Flags that are intended only for internal use,
such as
.BR FMODE_EXEC ,
can be set, and will consequently be set for the file descriptors
returned when reading from the fanotify file descriptor.
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR fanotify_mark (2),
.BR fanotify (7)
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