source: MondoRescue/branches/2.2.9/mindi-busybox/miscutils/inotifyd.c@ 2725

/* vi: set sw=4 ts=4: */
/*
 * simple inotify daemon
 * reports filesystem changes via userspace agent
 *
 * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */

/*
 * Use as follows:
 * # inotifyd /user/space/agent dir/or/file/being/watched[:mask] ...
 *
 * When a filesystem event matching the specified mask is occured on specified file (or directory)
 * a userspace agent is spawned and given the following parameters:
 * $1. actual event(s)
 * $2. file (or directory) name
 * $3. name of subfile (if any), in case of watching a directory
 *
 * E.g. inotifyd ./dev-watcher /dev:n
 *
 * ./dev-watcher can be, say:
 * #!/bin/sh
 * echo "We have new device in here! Hello, $3!"
 *
 * See below for mask names explanation.
 */

#include "libbb.h"
#include <sys/inotify.h>

static const char mask_names[] ALIGN1 =
    "a" // 0x00000001   File was accessed
    "c" // 0x00000002   File was modified
    "e" // 0x00000004   Metadata changed
    "w" // 0x00000008   Writable file was closed
    "0" // 0x00000010   Unwritable file closed
    "r" // 0x00000020   File was opened
    "m" // 0x00000040   File was moved from X
    "y" // 0x00000080   File was moved to Y
    "n" // 0x00000100   Subfile was created
    "d" // 0x00000200   Subfile was deleted
    "D" // 0x00000400   Self was deleted
    "M" // 0x00000800   Self was moved
    "\0"    // 0x00001000   (unused)
    // Kernel events, always reported:
    "u" // 0x00002000   Backing fs was unmounted
    "o" // 0x00004000   Event queued overflowed
    "x" // 0x00008000   File is no longer watched (usually deleted)
;
enum {
    MASK_BITS = sizeof(mask_names) - 1
};

int inotifyd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int inotifyd_main(int argc, char **argv)
{
    int n;
    unsigned mask;
    struct pollfd pfd;
    char **watches; // names of files being watched
    const char *args[5];

    // sanity check: agent and at least one watch must be given
    if (!argv[1] || !argv[2])
        bb_show_usage();

    argv++;
    // inotify_add_watch will number watched files
    // starting from 1, thus watches[0] is unimportant,
    // and 1st file name is watches[1].
    watches = argv;
    args[0] = *argv;
    args[4] = NULL;
    argc -= 2; // number of files we watch

    // open inotify
    pfd.fd = inotify_init();
    if (pfd.fd < 0)
        bb_perror_msg_and_die("no kernel support");

    // setup watches
    while (*++argv) {
        char *path = *argv;
        char *masks = strchr(path, ':');

        mask = 0x0fff; // assuming we want all non-kernel events
        // if mask is specified ->
        if (masks) {
            *masks = '\0'; // split path and mask
            // convert mask names to mask bitset
            mask = 0;
            while (*++masks) {
                const char *found;
                found = memchr(mask_names, *masks, MASK_BITS);
                if (found)
                    mask |= (1 << (found - mask_names));
            }
        }
        // add watch
        n = inotify_add_watch(pfd.fd, path, mask);
        if (n < 0)
            bb_perror_msg_and_die("add watch (%s) failed", path);
        //bb_error_msg("added %d [%s]:%4X", n, path, mask);
    }

    // setup signals
    bb_signals(BB_FATAL_SIGS, record_signo);

    // do watch
    pfd.events = POLLIN;
    while (1) {
        int len;
        void *buf;
        struct inotify_event *ie;
 again:
        if (bb_got_signal)
            break;
        n = poll(&pfd, 1, -1);
        // Signal interrupted us?
        if (n < 0 && errno == EINTR)
            goto again;
        // Under Linux, above if() is not necessary.
        // Non-fatal signals, e.g. SIGCHLD, when set to SIG_DFL,
        // are not interrupting poll().
        // Thus we can just break if n <= 0 (see below),
        // because EINTR will happen only on SIGTERM et al.
        // But this might be not true under other Unixes,
        // and is generally way too subtle to depend on.
        if (n <= 0) // strange error?
            break;

        // read out all pending events
        // (NB: len must be int, not ssize_t or long!)
        xioctl(pfd.fd, FIONREAD, &len);
#define eventbuf bb_common_bufsiz1
        ie = buf = (len <= sizeof(eventbuf)) ? eventbuf : xmalloc(len);
        len = full_read(pfd.fd, buf, len);
        // process events. N.B. events may vary in length
        while (len > 0) {
            int i;
            // cache relevant events mask
            unsigned m = ie->mask & ((1 << MASK_BITS) - 1);
            if (m) {
                char events[MASK_BITS + 1];
                char *s = events;
                for (i = 0; i < MASK_BITS; ++i, m >>= 1) {
                    if ((m & 1) && (mask_names[i] != '\0'))
                        *s++ = mask_names[i];
                }
                *s = '\0';
//              bb_error_msg("exec %s %08X\t%s\t%s\t%s", args[0],
//                  ie->mask, events, watches[ie->wd], ie->len ? ie->name : "");
                args[1] = events;
                args[2] = watches[ie->wd];
                args[3] = ie->len ? ie->name : NULL;
                spawn_and_wait((char **)args);
                // we are done if all files got final x event
                if (ie->mask & 0x8000) {
                    if (--argc <= 0)
                        goto done;
                    inotify_rm_watch(pfd.fd, ie->wd);
                }
            }
            // next event
            i = sizeof(struct inotify_event) + ie->len;
            len -= i;
            ie = (void*)((char*)ie + i);
        }
        if (eventbuf != buf)
            free(buf);
    } // while (1)
 done:
    return bb_got_signal;
}