Wednesday, December 05, 2007

Linux inotify example

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <sys/inotify.h>

void get_event (int fd, const char * target);
void handle_error (int error);

/* ----------------------------------------------------------------- */

int main (int argc, char *argv[])
char target[FILENAME_MAX];
int result;
int fd;
int wd; /* watch descriptor */

if (argc < 2) {
fprintf (stderr, "Watching the current directory\n");
strcpy (target, ".");
else {
fprintf (stderr, "Watching %s\n", argv[1]);
strcpy (target, argv[1]);

fd = inotify_init();
if (fd < 0) {
handle_error (errno);
return 1;

wd = inotify_add_watch (fd, target, IN_ALL_EVENTS);
if (wd < 0) {
handle_error (errno);
return 1;

while (1) {
get_event(fd, target);

return 0;

/* ----------------------------------------------------------------- */
/* Allow for 1024 simultanious events */
#define BUFF_SIZE ((sizeof(struct inotify_event)+FILENAME_MAX)*1024)

void get_event (int fd, const char * target)
ssize_t len, i = 0;
char action[81+FILENAME_MAX] = {0};
char buff[BUFF_SIZE] = {0};

len = read (fd, buff, BUFF_SIZE);

while (i < len) {
struct inotify_event *pevent = (struct inotify_event *)&buff[i];
char action[81+FILENAME_MAX] = {0};

if (pevent->len)
strcpy (action, pevent->name);
strcpy (action, target);

if (pevent->mask & IN_ACCESS)
strcat(action, " was read");
if (pevent->mask & IN_ATTRIB)
strcat(action, " Metadata changed");
if (pevent->mask & IN_CLOSE_WRITE)
strcat(action, " opened for writing was closed");
if (pevent->mask & IN_CLOSE_NOWRITE)
strcat(action, " not opened for writing was closed");
if (pevent->mask & IN_CREATE)
strcat(action, " created in watched directory");
if (pevent->mask & IN_DELETE)
strcat(action, " deleted from watched directory");
if (pevent->mask & IN_DELETE_SELF)
strcat(action, "Watched file/directory was itself deleted");
if (pevent->mask & IN_MODIFY)
strcat(action, " was modified");
if (pevent->mask & IN_MOVE_SELF)
strcat(action, "Watched file/directory was itself moved");
if (pevent->mask & IN_MOVED_FROM)
strcat(action, " moved out of watched directory");
if (pevent->mask & IN_MOVED_TO)
strcat(action, " moved into watched directory");
if (pevent->mask & IN_OPEN)
strcat(action, " was opened");

printf ("wd=%d mask=%d cookie=%d len=%d dir=%s\n",
pevent->wd, pevent->mask, pevent->cookie, pevent->len,
(pevent->mask & IN_ISDIR)?"yes":"no");

if (pevent->len) printf ("name=%s\n", pevent->name);

printf ("%s\n", action);

i += sizeof(struct inotify_event) + pevent->len;


} /* get_event */

/* ----------------------------------------------------------------- */

void handle_error (int error)
fprintf (stderr, "Error: %s\n", strerror(error));

} /* handle_error */

/* ----------------------------------------------------------------- */


Peter Teoh said...

Thank you for the example......fantastic sharing....I was searching for it.

Beket said...

Great example! Thanks!

Valeriano said...

Cool, now I try to run it on lenny

Mayur said...

It's very nice code, Thanks

Ivo said...

Just perfect. It is exactly the example I need.

Valeriano said...

Hello guys,

someone have a similar example that work on windows, in C or C++ ?

Clive said...

Of course! But the API is different. I'll generate a new post, its too big for a comment.

naren said...


shadyabhi said...

Thanx.. I really wanted a code like this..

Debsankha said...

Thanks for this code. The variable size of struct inotify_event causing all sorts of problems in my code and I was totally at a loss until I saw your example.

Annie Calvert said...

I loved your blog article.Really thank you! Will read on…

Jaga said...

can you explain this code functionality.i want to write php script to notify files

govardhan reddy said...

hi pal. i seen your program . it working for particular path like /tmp/Untitled Folder.
but i need to monitor subdirectory dynamically with out giving the command line arg.
eg: i monitored the " /media " path when ever i insert the usb(pen-drive) it shows.but i need to monitor that usb (pen-drive ) if i copy the file from system to pendrive or pen drive to system i need to monitor that thing ..please help me out .thanks in advance.

Sri said...

Hi, am getting the following error, at len = read (fd, buff, BUFF_SIZE);, that `read` was not declared in this scope? help me thanks...

Clive said...


#include <unistd.h>

Check with:

man 2 read

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