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io.flush() serves different purpose. it does only flush userspace
buffers implemented in stdio.h, not underlying OS/filesystem cache. And
fclose() is also triggering flush. So there's no reason to call
io.flush() immediately before io.close()...
https://github.com/lua/lua/blob/master/liolib.c#L725
static int io_flush (lua_State *L) {
return luaL_fileresult(L, fflush(getiofile(L, IO_OUTPUT)) == 0, NULL);
}
static int f_flush (lua_State *L) {
return luaL_fileresult(L, fflush(tofile(L)) == 0, NULL);
}
https://man7.org/linux/man-pages/man3/fflush.3.html
Note that fflush() flushes only the user-space buffers provided
by the C library. To ensure that the data is physically stored
on disk the kernel buffers must be flushed too, for example, with
sync(2) or fsync(2).
https://github.com/lua/lua/blob/master/liolib.c#L242
static int io_fclose (lua_State *L) {
LStream *p = tolstream(L);
int res = fclose(p->f);
return luaL_fileresult(L, (res == 0), NULL);
}
https://man7.org/linux/man-pages/man3/fclose.3.html
The fclose() function flushes the stream pointed to by stream
(writing any buffered output data using fflush(3)) and closes the
underlying file descriptor.
Dne 2022-09-19 18:06, DENIS napsal:
> fsync is not avaliable in io.*
>
> try to use flush()
>
> local f = io.open('file.txt', 'w')
>
> f:write('hello')
>
> F:FLUSH()
>
> f:close()
>
> f = nil
>
> ---- Em Seg, 19 set 2022 12:40:15 -0300 TOMAS MUDRUNKA
> <MUDRUNKA@SPOJE.NET> escreveu ---
>
>> Hello,
>> i have Lua script on Linux that opens file handle using io.open(),
>> writes to it using :write() and closes it using :close().
>>
>> I really need way to call fsync() on that file descriptor.
>> https://man7.org/linux/man-pages/man2/fsync.2.html
>>
>> Either as an argument, eg.: file:write(true) file:close(true)
>> or as separate call file:sync(). Is there way to do that?
>> If not, can you see this being added in the future?
>>
>> I know as a workaround i can call os.execute("sync");
>> But that triggers system wide sync of all files and filesystems,
>> which
>> is not really desirable.
>>
>> --
>> S pozdravem
>> Best regards
>> Tomáš Mudruňka
--
S pozdravem
Best regards
Tomáš Mudruňka - SPOJE.NET s.r.o.