man2/inotify_add_watch.2

   1 .\" Copyright (C) 2005 Robert Love
   2 .\" and Copyright, 2006 Michael Kerrisk
   3 .\"
   4 .\" SPDX-License-Identifier: GPL-2.0-or-later
   5 .\"
   6 .\" 2005-07-19 Robert Love <rlove@rlove.org> - initial version
   7 .\" 2006-02-07 mtk, various changes
   8 .\"
   9 .TH INOTIFY_ADD_WATCH 2 (date) "Linux man-pages (unreleased)"
  10 .SH NAME
  11 inotify_add_watch \- add a watch to an initialized inotify instance
  12 .SH LIBRARY
  13 Standard C library
  14 .RI ( libc ", " \-lc )
  15 .SH SYNOPSIS
  16 .nf
  17 .B #include <sys/inotify.h>
  18 .PP
  19 .BI "int inotify_add_watch(int " fd ", const char *" pathname ", uint32_t " mask );
  20 .fi
  21 .SH DESCRIPTION
  22 .BR inotify_add_watch ()
  23 adds a new watch, or modifies an existing watch,
  24 for the file whose location is specified in
  25 .IR pathname ;
  26 the caller must have read permission for this file.
  27 The
  28 .I fd
  29 argument is a file descriptor referring to the
  30 inotify instance whose watch list is to be modified.
  31 The events to be monitored for
  32 .I pathname
  33 are specified in the
  34 .I mask
  35 bit-mask argument.
  36 See
  37 .BR inotify (7)
  38 for a description of the bits that can be set in
  39 .IR mask .
  40 .PP
  41 A successful call to
  42 .BR inotify_add_watch ()
  43 returns a unique watch descriptor for this inotify instance,
  44 for the filesystem object (inode) that corresponds to
  45 .IR pathname .
  46 If the filesystem object
  47 was not previously being watched by this inotify instance,
  48 then the watch descriptor is newly allocated.
  49 If the filesystem object was already being watched
  50 (perhaps via a different link to the same object), then the descriptor
  51 for the existing watch is returned.
  52 .PP
  53 The watch descriptor is returned by later
  54 .BR read (2)s
  55 from the inotify file descriptor.
  56 These reads fetch
  57 .I inotify_event
  58 structures (see
  59 .BR inotify (7))
  60 indicating filesystem events;
  61 the watch descriptor inside this structure identifies
  62 the object for which the event occurred.
  63 .SH RETURN VALUE
  64 On success,
  65 .BR inotify_add_watch ()
  66 returns a watch descriptor (a nonnegative integer).
  67 On error, \-1 is returned and
  68 .I errno
  69 is set to indicate the error.
  70 .SH ERRORS
  71 .TP
  72 .B EACCES
  73 Read access to the given file is not permitted.
  74 .TP
  75 .B EBADF
  76 The given file descriptor is not valid.
  77 .TP
  78 .B EEXIST
  79 .I mask
  80 contains
  81 .B IN_MASK_CREATE
  82 and
  83 .I pathname
  84 refers to a file already being watched by the same
  85 .IR fd .
  86 .TP
  87 .B EFAULT
  88 .I pathname
  89 points outside of the process's accessible address space.
  90 .TP
  91 .B EINVAL
  92 The given event mask contains no valid events; or
  93 .I mask
  94 contains both
  95 .B IN_MASK_ADD
  96 and
  97 .BR IN_MASK_CREATE ;
  98 or
  99 .I fd
 100 is not an inotify file descriptor.
 101 .TP
 102 .B ENAMETOOLONG
 103 .I pathname
 104 is too long.
 105 .TP
 106 .B ENOENT
 107 A directory component in
 108 .I pathname
 109 does not exist or is a dangling symbolic link.
 110 .TP
 111 .B ENOMEM
 112 Insufficient kernel memory was available.
 113 .TP
 114 .B ENOSPC
 115 The user limit on the total number of inotify watches was reached or the
 116 kernel failed to allocate a needed resource.
 117 .TP
 118 .B ENOTDIR
 119 .I mask
 120 contains
 121 .B IN_ONLYDIR
 122 and
 123 .I pathname
 124 is not a directory.
 125 .SH VERSIONS
 126 Inotify was merged into the 2.6.13 Linux kernel.
 127 .SH STANDARDS
 128 This system call is Linux-specific.
 129 .SH EXAMPLES
 130 See
 131 .BR inotify (7).
 132 .SH SEE ALSO
 133 .BR inotify_init (2),
 134 .BR inotify_rm_watch (2),
 135 .BR inotify (7)