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Each file actually has a lock count associated with it. This allows nested calls by a task to acquire a file lock; each of those calls must be matched with a call to fs_funlockfile(). Listing - Example file lock usage shows how the file lock functions can be used.

Code Block

language	cpp
title	Listing - Example file lock usage
linenumbers	true

void  App_Fnct (void)
{
    unsigned  char  data1[50];
    unsigned  char  data2[10];
    .
    .
    .
   
    if (App_FilePtr != (FS_FILE *)0) {             (1)
        fs_flockfile(App_FilePtr);                 /* Lock file.                           */
                                                   
                                                   /* Wr data atomically.                  */
        fs_fwrite(data1, 1, sizeof(data1), App_FilePtr);
        fs_fwrite(data2, 1, sizeof(data1), App_FilePtr);
        fs_funlockfile(App_FilePtr);               /* Unlock file.                         */
    } 
    .
    .
    .
}

Panel
(1) `fs_flockfile()` will block the calling task until the file is available. If the task must write to the file only if no other task is currently accessing it, the non-blocking function `fs_funlockfile()` can be used.

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