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[thirdparty/man-pages.git] / man2 / inotify_add_watch.2

.\" Copyright (C) 2005 Robert Love
.\" and Copyright, 2006 Michael Kerrisk
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
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.\" 2005-07-19 Robert Love <rlove@rlove.org> - initial version
.\" 2006-02-07 mtk, various changes
.\"
.TH INOTIFY_ADD_WATCH 2 2010-10-20 "Linux" "Linux Programmer's Manual"
.SH NAME
inotify_add_watch \- add a watch to an initialized inotify instance
.SH SYNOPSIS
.B #include <sys/inotify.h>
.sp
.BI "int inotify_add_watch(int " fd ", const char *" pathname ", uint32_t " mask );
.SH DESCRIPTION
.BR inotify_add_watch ()
adds a new watch, or modifies an existing watch,
for the file whose location is specified in
.IR pathname ;
the caller must have read permission for this file.
The
.I fd
argument is a file descriptor referring to the
inotify instance whose watch list is to be modified.
The events to be monitored for
.I pathname
are specified in the
.I mask
bit-mask argument.
See
.BR inotify (7)
for a description of the bits that can be set in
.IR mask .

A successful call to
.BR inotify_add_watch ()
returns the unique watch descriptor associated with
.I pathname
for this inotify instance.
If
.I pathname
was not previously being watched by this inotify instance,
then the watch descriptor is newly allocated.
If
.I pathname
was already being watched, then the descriptor
for the existing watch is returned.

The watch descriptor is returned by later
.BR read (2)s
from the inotify file descriptor.
These reads fetch
.I inotify_event
structures (see
.BR inotify (7))
indicating file system events;
the watch descriptor inside this structure identifies
the object for which the event occurred.
.SH RETURN VALUE
On success,
.BR inotify_add_watch ()
returns a nonnegative watch descriptor.
On error \-1 is returned and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EACCES
Read access to the given file is not permitted.
.TP
.B EBADF
The given file descriptor is not valid.
.TP
.B EFAULT
.I pathname
points outside of the process's accessible address space.
.TP
.B EINVAL
The given event mask contains no valid events; or
.I fd
is not an inotify file descriptor.
.TP
.B ENOENT
A directory component in
.I pathname
does not exist or is a dangling symbolic link.
.TP
.B ENOMEM
Insufficient kernel memory was available.
.TP
.B ENOSPC
The user limit on the total number of inotify watches was reached or the
kernel failed to allocate a needed resource.
.SH VERSIONS
Inotify was merged into the 2.6.13 Linux kernel.
.SH CONFORMING TO
This system call is Linux-specific.
.SH SEE ALSO
.BR inotify_init (2),
.BR inotify_rm_watch (2),
.BR inotify (7)