NetBSDのfilemon機能で取得可能なファイルイベントをハンドリングするサンプルです。

nbsd_filemon_watch_any_event.c

/*
 * NetBSD filemonのファイル書き込みの監視サンプル。
 *
 *   $ gcc -Wall -Werror -g -o nbsd_filemon_watch_any_event nbsd_filemon_watch_any_event.c
 */

#include <dev/filemon/filemon.h>

#include <sys/wait.h>
#include <sys/ioctl.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <unistd.h>

extern char *optarg;
extern int optind;

void exec_handler_command(char *path, char *cmd)
{
    int status;

    switch(fork()) {
        case -1:
            fprintf(stderr, "cannot fork");
            break;
        case 0:
            if (cmd) {
                char *script[] = { cmd, path, NULL };
                execvp(script[0], script);
            }
        default:
            wait(&status);
    }
}

int main(int argc, char *argv[])
{
    int ch;
    char *c_cmd = NULL;  // chdir
    char *d_cmd = NULL;  // unlink
    char *e_cmd = NULL;  // exec
    char *f_cmd = NULL;  // fork,vfork
    char *l_cmd = NULL;  // link,sumlink
    char *m_cmd = NULL;  // rename
    char *r_cmd = NULL;  // open(RDONLY)
    char *w_cmd = NULL;  // open(RDWR)
    char *x_cmd = NULL;  // exit
    char *path = NULL;
    
    while ((ch = getopt(argc, argv, "c:d:e:f:l:m:r:w:x:")) != -1) {
        switch (ch) {
            case 'c': c_cmd = optarg; break;
            case 'd': d_cmd = optarg; break;
            case 'e': e_cmd = optarg; break;
            case 'f': f_cmd = optarg; break;
            case 'l': l_cmd = optarg; break;
            case 'm': m_cmd = optarg; break;
            case 'r': r_cmd = optarg; break;
            case 'w': w_cmd = optarg; break;
            case 'x': x_cmd = optarg; break;
            case '?':
            default:
                break;
        }
    }
    argc -= optind;
    argv += optind;

#if DEBUG
    if (c_cmd) printf("C: chdir        %s\n", c_cmd);
    if (d_cmd) printf("D: unlink       %s\n", d_cmd);
    if (e_cmd) printf("E: exec         %s\n", e_cmd);
    if (f_cmd) printf("F: fork,vfork   %s\n", f_cmd);
    if (l_cmd) printf("L: link,symlink %s\n", l_cmd);
    if (m_cmd) printf("M: rename       %s\n", m_cmd);
    if (r_cmd) printf("R: open(RDONLY) %s\n", r_cmd);
    if (w_cmd) printf("W: open(RDWR)   %s\n", w_cmd);
    if (x_cmd) printf("X: exit         %s\n", x_cmd);
#endif

    pid_t pid;
    int filemon_fd, temp_fd;
    int status;
    char temp_path[] = "/tmp/filemonXXXXXXXX";

    FILE *fp = NULL;
    char buf[BUFSIZ];
    int read_line = 0;
    int count = 0;
    int is_done = 0;

    filemon_fd = open("/dev/filemon", O_RDWR);
    temp_fd = mkstemp(temp_path);

    // give filemon the temp file to use
    ioctl(filemon_fd, FILEMON_SET_FD, &temp_fd);

    // children do not need these one they exec
    fcntl(filemon_fd, F_SETFD, FD_CLOEXEC);
    fcntl(temp_fd, F_SETFD, FD_CLOEXEC);

    pid = fork();
    switch(pid) {
        case -1:
            fprintf(stderr, "cannot fork");
            break;
        case 0:
            printf("filemon: %s\n", temp_path);
            pid = getpid();
            // tell filemon to monitor this process
            ioctl(filemon_fd, FILEMON_SET_PID, &pid);
            execvp(argv[0], argv);
            _exit(1);

            break;
        default:
           lseek(temp_fd, SEEK_SET, 0);

           is_done = 1;
           while (is_done) {
               fp = fopen(temp_path, "r");
               if (fp) {
                   count = 0;
                   while (fgets(buf, BUFSIZ-1, fp)) {
                       if (count++ < read_line) {
                           continue;
                       }

                       // "W 521 cal.txt" => "cal.txt"
                       path = buf;
                       //path = strchr(buf, ' ');
                       //path = strchr(++path, ' ');

                       switch (buf[0]) {
                           case 'C': exec_handler_command(path, c_cmd); break;
                           case 'D': exec_handler_command(path, d_cmd); break;
                           case 'E': exec_handler_command(path, e_cmd); break;
                           case 'F': exec_handler_command(path, f_cmd); break;
                           case 'L': exec_handler_command(path, l_cmd); break;
                           case 'M': exec_handler_command(path, m_cmd); break;
                           case 'R': exec_handler_command(path, r_cmd); break;
                           case 'W': exec_handler_command(path, w_cmd); break;
                           case 'X': exec_handler_command(path, x_cmd); break;
                           default: break;
                       }

                       if (buf[0] == '#') {
                           is_done = 0;
                           break;
                       }
                   }
                   read_line += count - read_line;

                   fclose(fp);
                   usleep(700000);
               }
           }

           wait(&status);
           close(filemon_fd);
           close(temp_fd);

           break;
    }

    return 0;
}