man2/inotify_add_watch.2

   1 .\" Copyright (C) 2005 Robert Love
   2 .\" and Copyright, 2006 Michael Kerrisk
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  25 .\" 2005-07-19 Robert Love <rlove@rlove.org> - initial version
  26 .\" 2006-02-07 mtk, various changes
  27 .\"
  28 .TH INOTIFY_ADD_WATCH 2 2019-03-06 "Linux" "Linux Programmer's Manual"
  29 .SH NAME
  30 inotify_add_watch \- add a watch to an initialized inotify instance
  31 .SH SYNOPSIS
  32 .B #include <sys/inotify.h>
  33 .PP
  34 .BI "int inotify_add_watch(int " fd ", const char *" pathname ", uint32_t " mask );
  35 .SH DESCRIPTION
  36 .BR inotify_add_watch ()
  37 adds a new watch, or modifies an existing watch,
  38 for the file whose location is specified in
  39 .IR pathname ;
  40 the caller must have read permission for this file.
  41 The
  42 .I fd
  43 argument is a file descriptor referring to the
  44 inotify instance whose watch list is to be modified.
  45 The events to be monitored for
  46 .I pathname
  47 are specified in the
  48 .I mask
  49 bit-mask argument.
  50 See
  51 .BR inotify (7)
  52 for a description of the bits that can be set in
  53 .IR mask .
  54 .PP
  55 A successful call to
  56 .BR inotify_add_watch ()
  57 returns a unique watch descriptor for this inotify instance,
  58 for the filesystem object (inode) that corresponds to
  59 .IR pathname .
  60 If the filesystem object
  61 was not previously being watched by this inotify instance,
  62 then the watch descriptor is newly allocated.
  63 If the filesystem object was already being watched
  64 (perhaps via a different link to the same object), then the descriptor
  65 for the existing watch is returned.
  66 .PP
  67 The watch descriptor is returned by later
  68 .BR read (2)s
  69 from the inotify file descriptor.
  70 These reads fetch
  71 .I inotify_event
  72 structures (see
  73 .BR inotify (7))
  74 indicating filesystem events;
  75 the watch descriptor inside this structure identifies
  76 the object for which the event occurred.
  77 .SH RETURN VALUE
  78 On success,
  79 .BR inotify_add_watch ()
  80 returns a nonnegative watch descriptor.
  81 On error, \-1 is returned and
  82 .I errno
  83 is set appropriately.
  84 .SH ERRORS
  85 .TP
  86 .B EACCES
  87 Read access to the given file is not permitted.
  88 .TP
  89 .B EBADF
  90 The given file descriptor is not valid.
  91 .TP
  92 .B EFAULT
  93 .I pathname
  94 points outside of the process's accessible address space.
  95 .TP
  96 .B EINVAL
  97 The given event mask contains no valid events; or
  98 .I mask
  99 contains both
 100 .B IN_MASK_ADD
 101 and
 102 .BR IN_MASK_CREATE ;
 103 or
 104 .I fd
 105 is not an inotify file descriptor.
 106 .TP
 107 .B ENAMETOOLONG
 108 .I pathname
 109 is too long.
 110 .TP
 111 .B ENOENT
 112 A directory component in
 113 .I pathname
 114 does not exist or is a dangling symbolic link.
 115 .TP
 116 .B ENOMEM
 117 Insufficient kernel memory was available.
 118 .TP
 119 .B ENOSPC
 120 The user limit on the total number of inotify watches was reached or the
 121 kernel failed to allocate a needed resource.
 122 .TP
 123 .B ENOTDIR
 124 .I mask
 125 contains
 126 .B IN_ONLYDIR
 127 and
 128 .I pathname
 129 is not a directory.
 130 .TP
 131 .B EEXIST
 132 .I mask
 133 contains
 134 .B IN_MASK_CREATE
 135 and
 136 .I pathname
 137 refers to a file already being watched by the same
 138 .IR fd .
 139 .SH VERSIONS
 140 Inotify was merged into the 2.6.13 Linux kernel.
 141 .SH CONFORMING TO
 142 This system call is Linux-specific.
 143 .SH SEE ALSO
 144 .BR inotify_init (2),
 145 .BR inotify_rm_watch (2),
 146 .BR inotify (7)