This third version of the patch considers comments by Michael Kerrisk
concerning
* alignment of inotify read buffer
On some systems integer values can only be read if they are
correctly aligned. Other system have a lower performance when
reading from or writing to misaligned memory positions.
An array of struct inotify_event is used to have the buffer
properly aligned. As on ILP64 systems int is 8 byte long
using aligned(4) may not be sufficient.
* simplification of loop over inotify event buffer
* typos
***
An example for the usage of the inotify API is provided.
It shows the usage of inotify_init1(2),inotify_add_watch(2) as well as
polling and reading from the inotify file descriptor.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@xxxxxx>
---
man7/inotify.7 | 221 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 220 insertions(+), 1 deletion(-)
diff --git a/man7/inotify.7 b/man7/inotify.7
index 8e848b2..2f21945 100644
--- a/man7/inotify.7
+++ b/man7/inotify.7
@@ -1,5 +1,6 @@
'\" t
.\" Copyright (C) 2006, 2014 Michael Kerrisk <mtk.manpages@xxxxxxxxx>
+.\" Copyright (C) 2014 Heinrich Schuchardt <xypron.glpk@xxxxxx>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
@@ -23,7 +24,7 @@
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
-.TH INOTIFY 7 2014-05-08 "Linux" "Linux Programmer's Manual"
+.TH INOTIFY 7 2014-05-23 "Linux" "Linux Programmer's Manual"
.SH NAME
inotify \- monitoring filesystem events
.SH DESCRIPTION
@@ -752,6 +753,224 @@ if the older had not yet been read)
instead checked if the most recent event could be coalesced with the
.I oldest
unread event.
+.SH EXAMPLE
+The following program demonstrates the usage of the inotify API.
+It marks the directories passed as a command-line arguments
+and waits for events of type
+.BR IN_OPEN ,
+.BR IN_CLOSE_NOWRITE
+and
+.BR IN_CLOSE_WRITE .
+.PP
+The following output was recorded while editing the file
+.I /home/user/temp/foo
+and listing directory
+.IR /tmp .
+Before the file and the directory were opened,
+.B IN_OPEN
+events occurred.
+After the file was closed, an
+.B IN_CLOSE_WRITE
+event occurred.
+After the directory was closed, an
+.B IN_CLOSE_NOWRITE
+event occurred.
+Execution of the program ended when the user pressed the ENTER key.
+.SS Example output
+.in +4n
+.nf
+$ ./inotify.7.example /tmp /home/user/temp
+Press enter key to terminate.
+Listening for events.
+IN_OPEN: /home/user/temp/foo [file]
+IN_CLOSE_WRITE: /home/user/temp/foo [file]
+IN_OPEN: /tmp/ [directory]
+IN_CLOSE_NOWRITE: /tmp/ [directory]
+
+Listening for events stopped.
+.fi
+.in
+.SS Program source
+.nf
+#include <errno.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/inotify.h>
+#include <unistd.h>
+
+/* Read all available inotify events from the file descriptor 'fd'.
+ wd is the table of watch descriptors for the directories in argv.
+ argc is the length of wd and argv.
+ argv is the list of watched directories.
+ Entry 0 of wd and argv is unused. */
+
+static void
+handle_events(int fd, int *wd, int argc, char* argv[])
+{
+ struct inotify_event buf[200];
+ const struct inotify_event *event;
+ int i;
+ ssize_t len;
+ char *ptr;
+
+ /* Loop while events can be read from inotify file descriptor. */
+
+ for (;;) {
+
+ /* Read some events. */
+
+ len = read(fd, buf, sizeof buf);
+ if (len == \-1 && errno != EAGAIN) {
+ perror("read");
+ exit(EXIT_FAILURE);
+ }
+
+ /* If the nonblocking read() found no events to read, then
+ it returns \-1 with errno set to EAGAIN. In that case,
+ we exit the loop. */
+
+ if (len <= 0)
+ break;
+
+ /* Loop over all events in the buffer */
+
+ for (ptr = (char *) buf; ptr < (char *) buf + len;
+ ptr += sizeof(struct inotify_event) + event\->len) {
+
+ event = (const struct inotify_event *) ptr;
+
+ /* Print event type */
+
+ if (event\->mask & IN_OPEN)
+ printf("IN_OPEN: ");
+ if (event\->mask & IN_CLOSE_NOWRITE)
+ printf("IN_CLOSE_NOWRITE: ");
+ if (event\->mask & IN_CLOSE_WRITE)
+ printf("IN_CLOSE_WRITE: ");
+
+ /* Print the name of the watched directory */
+
+ for (i = 1; i < argc; ++i) {
+ if (wd[i] == event\->wd) {
+ printf("%s/", argv[i]);
+ break;
+ }
+ }
+
+ /* Print the name of the file */
+
+ if (event\->len)
+ printf("%s", event\->name);
+
+ /* Print type of filesystem object */
+
+ if (event\->mask & IN_ISDIR)
+ printf(" [directory]\\n");
+ else
+ printf(" [file]\\n");
+
+ }
+ }
+}
+
+int
+main(int argc, char* argv[])
+{
+ char buf;
+ int fd, i, poll_num;
+ int *wd;
+ nfds_t nfds;
+ struct pollfd fds[2];
+
+ if (argc < 2) {
+ printf("Usage: %s DIRECTORY [DIRECTORY ...]\\n", argv[0]);
+ exit(EXIT_FAILURE);
+ }
+
+ printf("Press ENTER key to terminate.\\n");
+
+ /* Create the file descriptor for accessing the inotify API */
+
+ fd = inotify_init1(IN_NONBLOCK);
+ if (fd == \-1) {
+ perror("inotify_init1");
+ exit(EXIT_FAILURE);
+ }
+
+ /* Allocate memory for watch descriptors */
+
+ wd = calloc(argc, sizeof(int));
+ if (wd == NULL) {
+ perror("calloc");
+ exit(EXIT_FAILURE);
+ }
+
+ /* Mark directories for events
+ \- file was opened
+ \- file was closed */
+
+ for (i = 1; i < argc; i++) {
+ wd[i] = inotify_add_watch(fd, argv[i],
+ IN_OPEN | IN_CLOSE);
+ if (wd[i] == \-1) {
+ fprintf(stderr, "Cannot watch '%s'\\n", argv[i]);
+ perror("inotify_add_watch");
+ exit(EXIT_FAILURE);
+ }
+ }
+
+ /* Prepare for polling */
+
+ nfds = 2;
+
+ /* Console input */
+
+ fds[0].fd = STDIN_FILENO;
+ fds[0].events = POLLIN;
+
+ /* Inotify input */
+
+ fds[1].fd = fd;
+ fds[1].events = POLLIN;
+
+ /* Wait for events and/or terminal input */
+
+ printf("Listening for events.\\n");
+ while (1) {
+ poll_num = poll(fds, nfds, \-1);
+ if (poll_num == \-1) {
+ if (errno == EINTR)
+ continue;
+ perror("poll");
+ exit(EXIT_FAILURE);
+ }
+ if (poll_num > 0) {
+
+ if (fds[0].revents & POLLIN) {
+
+ /* Console input is available. Empty stdin and quit */
+
+ while (read(STDIN_FILENO, &buf, 1) > 0 && buf != '\\n')
+ continue;
+ break;
+ }
+ if (fds[1].revents & POLLIN) {
+
+ /* Inotify events are available */
+ handle_events(fd, wd, argc, argv);
+ }
+ }
+ }
+
+ /* Close inotify file descriptor */
+
+ close(fd);
+ free(wd);
+ printf("Listening for events stopped.\\n");
+ exit(EXIT_SUCCESS);
+}
+.fi
.SH SEE ALSO
.BR inotifywait (1),
.BR inotifywatch (1),
--
2.0.0.rc2
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
