NAME

SYNOPSIS

int
inotify_init();

int
inotify_init1(int flags);

int
inotify_add_watch(int fd, const char *pathname, uint32_t mask);

int
inotify_rm_watch(int fd, int wd);

int
libinotify_set_param(int fd, int param, intptr_t value);

DESCRIPTION

IN_NONBLOCK

Set I_NONBLOCK file status flag on the inotify file descriptor.

IN_CLOSEXEC

Set FD_CLOEXEC flag on the new file descriptor. See O_CLOEXEC flag in open(2)

The function returns the file descritor to the inotify handle if successful otherwise return -1. Possible errorno values are -

EINVAL

Invalid flag value passed.

EMFILE

System wide limit of inotify instances reached.

ENFILE

System limit on total number of fd's reached.

ENOMEM

Insufficient kernel memory.

inotify_add_watch() function adds news watch to the inotify instance. List of possible masks are described below. If the watch for given filename already exists, it it updated with the new mask value passed. The function returns an integer called watch descriptor if successful otherwise -1.

Possible values for errorno are -

EACCES

Permission for read access is denied for given file.

EBADF

Invalid file descriptor.

EFAULT

Pathname points outside process's allocated address space.

EINVAL

Invalid event mask passed.

ENOENT

A component of path that must exist does not exist.

ENOMEM

Insufficient kernel memory available.

ENOSPC

User limit on total number of inotify watches has crossed or kernel failed to allocate a needed resource.

inotify_rm_watch() function removes watch wd from the instance described by file descriptor fd. The function returns zero on sucess and -1 on error. Possible errorno values are -

EBADF

Invalid file descriptor fd.

EINVAL

Invalid watch descriptor wd.

libinotify_set_param() Libinotify specific. Replacement for Linux procfs interface. Set inotify parameter for the instance described by file descriptor fd. fd value of -1 is used for setting of global parameters. Possible param values are -

IN_SOCKBUFSIZE

Size of communication socket buffer in bytes. Should match read(2) buffer size for libinotify event consumers. Lower values can cause partial event reads. Bigger values is just a wasting of memory. Default value is arbitrary, has been acquired from code sample in linux inotify(7) man page and seems to be very common among the inotify clients. Default value 4096 (exported as IN_DEF_SOCKBUFSIZE)

IN_MAX_QUEUED_EVENTS

Upper limit on the queue length per inotify handle. linux`s /proc/sys/fs/inotify/max_queued_events counterpart. Default value 16384 (exported as IN_DEF_MAX_QUEUED_EVENTS)

IN_MAX_USER_INSTANCES

Global upper limit on the number of inotify instances that can be created. linux`s /proc/sys/fs/inotify/max_user_instances counterpart. Default value 2147483646 (exported as IN_DEF_MAX_USER_INSTANCES)

inotify_event structure

struct inotify_event {
    int         wd;       /* Watch descriptor */
    uint32_t    mask;     /* Mask of events */
    uint32_t    cookie;   /* Unique integer associating related events */
    uint32_t    len;      /* Size of name field */
    char        name[];   /* Optional null-terminated name */
};

inotify events -

IN_OPEN             File was opened.
IN_ACCESS           File was accessed (read).
IN_ATTRIB           Metadata changed.
IN_CREATE           File/directory was created in watched directory.
IN_CLOSE_WRITE      File opened for writing was closed.
IN_CLOSE_NOWRITE    File not opened for writing was closed.
IN_DELETE           File/directory in watched directory was deleted.
IN_DELETE_SELF      Watched file/directory was deleted.
IN_MODIFY           File/Directory was modified.
IN_MOVE_SELF        Watched file/directory was moved.
IN_MOVED_FROM       A file in watched directory was moved out.
IN_MOVED_TO         A file was moved into watched directory.
IN_ALL_EVENTS       Bit mask of all the above events.
IN_MOVE             Equal to IN_MOVED_FROM|IN_MOVED_TO
IN_CLOSE            Equal to IN_CLOSE_WRITE|IN_CLOSE_NOWRITE

IN_DELETE_SELF and IN_MOVE_SELF can occur only for watched file/directory. Other events can be marked for a file/directory in a watched direcotry. In that case the name of the file for which event is generated can be read by 'name' field in inotify_event structure.

Following are additional bits that can be set in mask when calling inotify_add_watch() -

IN_DONT_FOLLOW

Don't derefernce path name if its symlink.

IN_EXCL_UNLINK

Do not generate events for unlinked childrens. (Currently not supported).

IN_MASK_ADD

Add event mask for watch for given pathname.

IN_ONESHOT

Remove watch after retrieving one event.

IN_ONLYDIR

Only watch the pathname if it is a directory.

Following bits may be set by mask field returned by read(3)

IN_IGNORED

Watch for removed (explicitely, revoked or unmounted).

IN_ISDIR

Subject of this event is a directory.

IN_Q_OVERFLOW

Event queue has overflowed.

IN_UNMOUNT

File system containing watched file/directory was unmounted.

SEE ALSO

HISTORY