客戶需要將轉碼器中電視直播頻道的hls切片轉存出來，在拷貝文件時，需要判斷該切片文件是否正在被寫入，否則拷貝出來的切片文件不完整。

linux下程序fuser有這個功能，源碼在psmisc包裏，地址：https://gitlab.com/psmisc/psmisc，

fuser功能很強大，可以查找文件，目錄，網絡端口等，我們只用到文件部分

原理是遍歷/proc下的進程目錄，和fd中的描述符做比較

關鍵函數如下：

 1 static void
 2 check_dir(const pid_t pid, const char *dirname, struct device_list *dev_head,
 
 3       struct inode_list *ino_head, const uid_t uid, const char access,
 4       dev_t netdev)
 5 {
 6     char *dirpath, *filepath;
 7     DIR *dirp;
 8     struct dirent *direntry;
 9     struct inode_list *ino_tmp;
10     struct device_list *dev_tmp;
11     struct stat st, lst;
12 
13     if ((dirpath = malloc
 
(MAX_PATHNAME)) == NULL)
14         return;
15     if ((filepath = malloc(MAX_PATHNAME)) == NULL)
16         return;
17 
18     snprintf(dirpath, MAX_PATHNAME, "/proc/%d/%s", pid, dirname);
19     if ((dirp = opendir(dirpath)) == NULL)
20         return;
21     while ((direntry = readdir(dirp)) != NULL) {
 
22         if (direntry->d_name[0] < ‘0‘ || direntry->d_name[0] > ‘9‘)
23             continue;
24 
25         snprintf(filepath, MAX_PATHNAME, "/proc/%d/%s/%s",
26              pid, dirname, direntry->d_name);
27         if (stat(filepath, &st) != 0) {
28             fprintf(stderr, "Cannot stat file %s: %s\n",
29                 filepath, strerror(errno));
30         } 
31         else 
32         {
33             for (dev_tmp = dev_head; dev_tmp != NULL;
34                  dev_tmp = dev_tmp->next) {
35                 if (st.st_dev == dev_tmp->device) {
36                     if (access == ACCESS_FILE
37                         && (lstat(filepath, &lst) == 0)
38                         && (lst.st_mode & S_IWUSR)) {
39                         add_matched_proc(dev_tmp->name,
40                                  pid, uid,
41                                  ACCESS_FILEWR |
42                                  access);
43                     } else {
44                         add_matched_proc(dev_tmp->name,
45                                  pid, uid,
46                                  access);
47                     }
48                 }
49             }
50             for (ino_tmp = ino_head; ino_tmp != NULL;
51                  ino_tmp = ino_tmp->next) {
52                 if (st.st_dev == ino_tmp->device
53                     && st.st_ino == ino_tmp->inode) {
54                     if (access == ACCESS_FILE
55                         && (lstat(filepath, &lst) == 0)
56                         && (lst.st_mode & S_IWUSR)) {
57                         add_matched_proc(ino_tmp->name,
58                                  pid, uid,
59                                  ACCESS_FILEWR |
60                                  access);
61                     } else {
62                         add_matched_proc(ino_tmp->name,
63                                  pid, uid,
64                                  access);
65                     }
66                 }
67             }
68         }
69     }            /* while fd_dent */
70     closedir(dirp);
71 }

運行結果：

ps：

同學們測試時如使用vi打開文件，但是fuser未顯示文件被占用，原因如下：

linux 判斷文件被其他進程占用