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Diffstat (limited to 'usr/src/man/man5/inotify.5')
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diff --git a/usr/src/man/man5/inotify.5 b/usr/src/man/man5/inotify.5 new file mode 100644 index 0000000000..9b0016101d --- /dev/null +++ b/usr/src/man/man5/inotify.5 @@ -0,0 +1,305 @@ +'\" te +.\" Copyright (c) 2014, Joyent, Inc. All Rights Reserved. +.\" This file and its contents are supplied under the terms of the +.\" Common Development and Distribution License ("CDDL"), version 1.0. +.\" You may only use this file in accordance with the terms of version +.\" 1.0 of the CDDL. +.\" +.\" A full copy of the text of the CDDL should have accompanied this +.\" source. A copy of the CDDL is also available via the Internet at +.\" http://www.illumos.org/license/CDDL. +.TH INOTIFY 5 "Sep 17, 2014" +.SH NAME +inotify \- Linux-compatible file event notification facility +.SH SYNOPSIS + +.LP +.nf +#include <sys/inotify.h> +.fi + +.SH DESCRIPTION +.sp +.LP + +\fBinotify\fR is a facility for receiving file system events on specified +files or directories. When monitoring a directory, \fBinotify\fR can be +used to retrieve events not only on the directory, but also on any files +that the directory contains. \fBinotify\fR originated with Linux, and +this facility is designed to be binary-compatible with the Linux facility, +including the following interfaces: + +.RS +4 +.TP +.ie t \(bu +.el o +\fBinotify_init\fR(3C) creates an \fBinotify\fR instance, returning a file +descriptor associated with the in-kernel event queue. +.RE +.RS +4 +.TP +.ie t \(bu +.el o +\fBinotify_init1\fR(3C) also creates an \fBinotify\fR instance, but allows +for a flags argument that controls some attributes of the returned file +descriptor. +.RE +.RS +4 +.TP +.ie t \(bu +.el o +\fBinotify_add_watch\fR(3C) allows a watch of a particular file or directory +to be added to a watch list associated with the specified \fBinotify\fR +instance. \fBinotify_add_watch\fR(3C) returns a watch descriptor that will +be reflected in the \fIwd\fR member of the \fIinotify_event\fR structure +returned via a \fBread\fR(2) of the instance. +.RE +.RS +4 +.TP +.ie t \(bu +.el o +\fBinotify_rm_watch\fR(3C) removes the watch that corresponds to the specified +watch descriptor. +.RE + +When all file descriptors referring to a particular \fBinotify\fR instance +are closed, the instance and all watches associated with that instance are +freed. + +To consume events on an \fBinotify\fR instance, an application should +issue a \fBread\fR(2) to the instance. If no events are available +(and the \fBinotify\fR instance has not been explicitly made non-blocking +via \fBinotify_init1\fR(3C)) the \fBread\fR(2) will block until a +watched event occurs. If and when events are available, \fBread\fR(2) will +return an array of the following structures: + +.sp +.in +2 +.nf +struct inotify_event { + int wd; /* watch descriptor */ + uint32_t mask; /* mask of event */ + uint32_t cookie; /* cookie for associating renames */ + uint32_t len; /* size of name field */ + char name[]; /* optional name */ +}; +.fi +.in -2 + +\fIwd\fR contains the watch descriptor that corresponds to the event, +as returned by \fBinotify_add_watch\fR(3C). + +\fImask\fR is a bitwise \fBOR\fR of event masks (see below) that +describes the event. + +\fIcookie\fR is an opaque value that can be used to associate different +events into a single logical event. In particular, it allows consumers to +associate \fBIN_MOVED_FROM\fR events with subsequent \fBIN_MOVED_TO\fR +events. + +\fIlen\fR denotes the length of the \fIname\fR field, including any padding +required for trailing null bytes and alignment. The size of the entire +event is therefore the size of the \fIinotify_event\fR structure plus the +value of \fIlen\fR. + +\fIname\fR contains the name of the file associated with the event, if any. +This field is only present when the watched entity is a directory and +the event corresponds to a file that was contained by the watched directory +(though see \fBNOTES\fR and \fBWARNINGS\fR for details and limitations). +When present, \fIname\fR is null terminated, and may contain additional +zero bytes +to pad for alignment. (The length of this field -- including any bytes +for alignment -- is denoted by the \fIlen\fR field.) + +.SS "Events" + +The events that can be generated on a watched entity are as follows: + +.sp +.in +2 +.TS +c c +l l . +\fIEvent\fR \fIDescription\fR +\fBIN_ACCESS\fR File/directory was accessed +\fBIN_ATTRIB\fR File/directory attributes were changed +\fBIN_CLOSE_WRITE\fR File/directory opened for writing was closed +\fBIN_CLOSE_NOWRITE\fR File/directory not opened for writing was closed +\fBIN_CREATE\fR File/directory created in watched directory +\fBIN_DELETE\fR File/directory deleted from watched directory +\fBIN_DELETE_SELF\fR Watched file/directory was deleted +\fBIN_MODIFY\fR File/directory was modified +\fBIN_MODIFY_SELF\fR Watched file/directory was modified +\fBIN_MOVED_FROM\fR File was renamed from entity in watched directory +\fBIN_MOVED_TO\fR File was renamed to entity in watched directory +\fBIN_OPEN\fR File/directory was opened +.TE +.in -2 + +Of these, all events except \fBIN_MOVE_SELF\fR and \fBIN_DELETE_SELF\fR +can refer to either the watched entity or (if the watched entity +is a directory) a file or directory contained by the watched directory. +(See \fBNOTES\fR and \fBWARNINGS\fR, below for details on this +mechanism and its limitations.) +If the event corresponds to a contained entity, +\fIname\fR will be set to the name of the affected +entity. + +In addition to speciyfing events of interest, watched events may +be modified by potentially setting any of the following when adding a +watch via \fBinotify_add_watch\fR(3C): + +.sp +.ne 2 +.na +\fBIN_DONT_FOLLOW\fR +.ad +.RS 12n +Don't follow the specified pathname if it is a symbolic link. +.RE + +.sp +.ne 2 +.na +\fBIN_EXCL_UNLINK\fR +.ad +.RS 12n +If watching a directory and a contained entity becomes unlinked, cease +generating events for that entity. (By default, contained entities will +continue to generate events on their former parent directory.) +.RE + +.sp +.ne 2 +.na +\fBIN_MASK_ADD\fR +.ad +.RS 12n +If the specified pathname is already being watched, the specified events +will be added to the watched events instead of the default behavior of +replacing them. (If one +may forgive the editorializing, this particular interface gewgaw +seems entirely superfluous, and a canonical example of +feasibility trumping wisdom.) +.RE + +.sp +.ne 2 +.na +\fBIN_ONESHOT\fR +.ad +.RS 12n +Once an event has been generated for the watched entity, remove the +watch from the watch list as if \fBinotify_rm_watch\fR(3C) had been called +on it (thereby inducing an \fBIN_IGNORED\fR event). +.RE + +.sp +.ne 2 +.na +\fBIN_ONLYDIR\fR +.ad +.RS 12n +Only watch the specified pathname if it is a directory. +.RE + +In addition to the specified events, the following bits may be specified +in the \fImask\fR field as returned from \fBread\fR(2): + +.sp +.ne 2 +.na +\fBIN_IGNORED\fR +.ad +.RS 12n +A watch was removed explicitly (i.e, via \fBinotify_rm_watch\fR(3C)) or +implicitly (e.g., because \fBIN_ONESHOT\fR was set or because the watched +entity was deleted). +.RE + +.sp +.ne 2 +.na +\fBIN_ISDIR\fR +.ad +.RS 12n +The entity inducing the event is a directory. +.RE + +.sp +.ne 2 +.na +\fBIN_Q_OVERFLOW\fR +.ad +.RS 12n +The event queue exceeded the maximum event queue length per instance. +(By default, this is 16384, but it can be tuned by setting +\fBinotify_maxevents\fR via \fB/etc/system\fR.) +.RE + +.sp +.ne 2 +.na +\fBIN_UNMOUNT\fR +.ad +.RS 12n +The filesystem containing the watched entity was unmounted. +.RE + +.sp +.SH NOTES +.sp +.LP + +\fBinotify\fR instances can be monitored via \fBpoll\fR(2), +\fBport_get\fR(3C), \fBepoll\fR(5), etc. + +The event queue associated with an \fBinotify\fR instance is serialized +and ordered: events will be placed on the tail of the queue in the order +that they occur. + +If at the time an event occurs the tail of the event queue is identical +to the newly received event, the newly received event will be dropped, +effectively coalescing the two events. + +When watching a directory and receieving events on contained elements +(i.e., a contained file or subdirectory), note that the information +received in the \fIname\fR field may be stale: the file may have been +renamed between the event and its processing. If a file has been unlinked +(and if \fBIN_EXCL_UNLINK\fR has not been set), +the \fIname\fR will reflect the last name that resolved to the file. +If a new file is created in the same directory with the old name, events +on the new file and the old (unlinked) file will become undistinguishable. + +The number of bytes that are available to be read on an \fBinotify\fR +instance can be determined via a \fBFIONREAD\fR \fBioctl\fR(2). + +.sp +.SH WARNINGS +.sp +.LP + +While a best effort has been made to mimic the Linux semantics, there +remains a fundamental difference with respect to hard links: on Linux, +if a file has multiple hard links to it, a notification on a watched +directory or file will be received if and only if that event was received +via the watched path. For events that are induced by open files +(such as \fBIN_MODIFY\fR), these semantics seem peculiar: the watched +file is in fact changing, but because it is not changing via the watched +path, no notification is received. By contrast, the implementation here +will always yield an event in this case -- even if the event was induced +by an \fBopen\fR(2) via an unwatched path. If an event occurs within a +watched directory on a file for which there exist multiple hard links within +the same (watched) directory, the event's \fIname\fR will correspond to one +of the links to the file. If multiple hard links exist to the +same file in the same watched directory and one of the links is removed, +notifications may not necessarily continue to be received for the file, +despite the (remaining) link in the watched directory; users of +\fBinotify\fR should exercise extreme caution when watching directories +that contain files with multiple hard links in the same directory. + +.SH SEE ALSO +.sp +.LP +\fBinotify_init\fR(3C), \fBinotify_init1\fR(3C), \fBinotify_add_watch\fR(3C), +\fBinotify_rm_watch\fR(3C), \fBport_get\fR(3C), \fBepoll\fR(5) |