监控文件夹A，若文件夹中的B文件发生变化，则执行C命令。Linux下可以通过inotify完成该功能。
1，相关函数
inotify_init() - 创建一个inotify实例 inotify_add_watch(int fd, const char *pathname, uint32_t mask) - 加入文件或目录到inotify进行监测 inotify_rm_watch(int fd, int wd) - 移除一个watcher
2，相关结构
struct inotify_event { int wd; /* Watch descriptor */ uint32_t mask; /* Mask of events */ uint32_t cookie; /* Unique cookie associating related events (for rename(2)) */ uint32_t len; /* Size of name field */ char name[]; /* Optional null-terminated name */ };
3，Mask
适用于 inotify_add_watch mask 与 read 返回的inotify_event中mask
IN_ACCESS文件被访问
IN_ATTRIB文件属性发生变化
IN_CLOSE_WRITE以write方式打开文件并关闭
IN_CLOSE_NOWRITE以非write方式打开文件并关闭
IN_CREATE文件或目录被创建
IN_DELETE文件或目录被删除（被监测的文件夹A中B文件被删除）
IN_DELETE_SELF被监测的文件或目录被删除（被监测的文件夹A被删除）
IN_MODIFY文件被修改
IN_MOVE_SELF被监测的文件或目录移动
IN_MOVED_FROM文件移出被监测的目录
IN_MOVED_TO文件移入被监测的目录
IN_OPEN文件被打开
上述flag的集合
IN_ALL_EVENTS以上所有flag的集合
IN_MOVEIN_MOVED_TO|IN_MOVED_FROM
IN_CLOSEIN_CLOSE_WRITE|IN_CLOSE_NOWRITE
不常用的flag
IN_DONT_FOLLOW不follow符号链接 (since 2.6.15)
IN_EXCL_UNLINK当文件从监测目中unlink后，则不再报告该文件的相关event，比如监控/tmp使用 (since 2.6.36)
IN_MASK_ADD追打MASK到被监测的pathname
IN_ONESHOT只监测一次
IN_ONLYDIR只监测目录
仅由read返回
IN_IGNOREDinotify_rm_watch，文件被删除或者文件系统被umount
IN_ISDIR发生事件的是一个目录
IN_Q_OVERFLOWEvent队列溢出
IN_UNMOUNT文件系统unmount
4，例子
用途：监测指定文件或目录（或不指定则为当前目录）的一切动作。
使用：inotify [文件或目录]
#include #include #include #include #include #include #include #define ERROR(text) error(1, errno, "%s", text) struct EventMask { int flag; const char *name; }; int freadsome(void *dest, size_t remain, FILE *file) { char *offset = (char*)dest; while (remain) { int n = fread(offset, 1, remain, file); if (n == 0) { return -1; } remain -= n; offset += n; } return 0; } //http://www.ibm.com/developerworks/cn/linux/l-inotify/ //http://www.jiangmiao.org/blog/2179.html int main(int argc, char *argv[]) { const char *target; if (argc == 1) { target ="."; } else { target = argv[1]; } struct EventMask event_masks[] = { { IN_ACCESS,"IN_ACCESS" }, { IN_ATTRIB,"IN_ATTRIB" }, { IN_CLOSE_WRITE,"IN_CLOSE_WRITE" }, { IN_CLOSE_NOWRITE,"IN_CLOSE_NOWRITE" }, { IN_CREATE,"IN_CREATE" }, { IN_DELETE,"IN_DELETE" }, { IN_DELETE_SELF,"IN_DELETE_SELF" }, { IN_MODIFY,"IN_MODIFY" }, { IN_MOVE_SELF,"IN_MOVE_SELF" }, { IN_MOVED_FROM,"IN_MOVED_FROM" }, { IN_MOVED_TO,"IN_MOVED_TO" }, { IN_OPEN,"IN_OPEN" }, { IN_DONT_FOLLOW,"IN_DONT_FOLLOW" }, //{ IN_EXCL_UNLINK, "IN_EXCL_UNLINK" }, { IN_MASK_ADD,"IN_MASK_ADD" }, { IN_ONESHOT,"IN_ONESHOT" }, { IN_ONLYDIR,"IN_ONLYDIR" }, { IN_IGNORED,"IN_IGNORED" }, { IN_ISDIR,"IN_ISDIR" }, { IN_Q_OVERFLOW,"IN_Q_OVERFLOW" }, { IN_UNMOUNT,"IN_UNMOUNT" }, }; int monitor = inotify_init(); if (-1 == monitor) { ERROR("monitor"); } int watcher = inotify_add_watch(monitor, target, IN_ALL_EVENTS); if (-1 == watcher) { ERROR("inotify_add_watch error"); } FILE *monitor_file = fdopen(monitor, "r"); char last_name[1024]; char name[1024]; /* event:inotify_event -> name:char[event.len] */ while (true) { struct inotify_event event; if (-1 == freadsome(&event, sizeof(event), monitor_file)) { ERROR("freadsome error"); } if (event.len) { freadsome(name, event.len, monitor_file); } else { sprintf(name,"FD: %d\n", event.wd); } if (strcmp(name, last_name) != 0) { puts(name); strcpy(last_name, name); } /* 显示event的mask的含义 */ int i = 0; for (i = 0; i < sizeof(event_masks) / sizeof(struct EventMask); ++i) { if (event.mask & event_masks[i].flag) { printf("\t%s\n", event_masks[i].name); } } } return 0; }
下面的例子来源于inotify_tools的示例代码，但是做了一些改进。inotify_tools监视一个目录时，可以得到该目录变化的信息。但是在该目录下，创建一个子目录后，子目录中的变化，inotify_tools不能获取。所以我添加了动态监控目录的代码。
#include #include #include #include enum { ACTION_NULL_WD, ACTION_ADD_WD, ACTION_DEL_WD, }; int main(int argc, const char **argv) { int err = 0; if (!inotifytools_initialize()) { printf("inotifytools_initialize failedn"); goto error; } inotifytools_initialize_stats(); const char *monitor_path = "."; if (argc > 1) { monitor_path = argv[1]; } printf("Monitor dir(%s)n", monitor_path); if (!inotifytools_watch_recursively(monitor_path, IN_ALL_EVENTS)) { printf("inotifytools_watch_recursively failedn"); goto error; } inotifytools_set_printf_timefmt("%F %T"); struct inotify_event * event = inotifytools_next_event(-1); char path[256]; while (event) { inotifytools_printf( event, "%T %w%f %en" ); if (IN_ISDIR&event->mask) { int action = ACTION_NULL_WD; if ((IN_DELETE|IN_DELETE_SELF|IN_MOVED_FROM)&event->mask) { action = ACTION_DEL_WD; snprintf(path, sizeof(path), "%s%s", inotifytools_filename_from_wd(event->wd), event->name); printf("Remove path(%s) from wdn", path); } else if (((IN_CREATE|IN_MOVED_TO)&event->mask) && (IN_ISDIR&event->mask)) { action = ACTION_ADD_WD; snprintf(path, sizeof(path), "%s%s", inotifytools_filename_from_wd(event->wd), event->name); printf("Add path(%s) into wdn", path); } if (ACTION_ADD_WD == action) { if (!inotifytools_watch_recursively(path, IN_ALL_EVENTS)) { printf("inotifytools_watch_recursively failedn"); goto error; } } else if (ACTION_DEL_WD == action) { if (!inotifytools_remove_watch_by_wd(event->wd)) { printf("inotifytools_remove_watch_by_wd failed. event->wd(%d)n", event->wd); goto error; } } } event = inotifytools_next_event(-1); } printf("Exitn"); return 0; error: err = inotifytools_error(); printf("Error(%d)n", err); return -1; }
