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-rw-r--r--lib/kernel/doc/src/file.xml10
-rw-r--r--lib/kernel/src/file.erl3
-rw-r--r--lib/kernel/test/file_SUITE.erl14
3 files changed, 26 insertions, 1 deletions
diff --git a/lib/kernel/doc/src/file.xml b/lib/kernel/doc/src/file.xml
index 1118a8feee..0a4dd3ba47 100644
--- a/lib/kernel/doc/src/file.xml
+++ b/lib/kernel/doc/src/file.xml
@@ -826,6 +826,16 @@
<item>
<p><c>File</c> must be <c>iodata()</c>. Returns an <c>fd()</c> which lets the <c>file</c> module operate on the data in-memory as if it is a file.</p>
</item>
+ <tag><c>sync</c></tag>
+ <item>
+ <p>On platforms that support it, enables the POSIX <c>O_SYNC</c> synchronous I/O flag or its platform-dependent
+ equivalent (e.g., <c>FILE_FLAG_WRITE_THROUGH</c> on Windows) so that writes to the file block until the data has
+ been physically written to disk. Be aware, though, that the exact semantics of this flag differ from platform to
+ platform; for example, neither Linux nor Windows guarantees that all file metadata are also written before the call
+ returns. For precise semantics, check the details of your platform's documentation. On platforms with no
+ support for POSIX <c>O_SYNC</c> or equivalent, use of the <c>sync</c> flag causes <c>open</c> to return
+ <c>{error, enotsup}</c>.</p>
+ </item>
</taglist>
<p>Returns:</p>
<taglist>
diff --git a/lib/kernel/src/file.erl b/lib/kernel/src/file.erl
index 5c0f3b7ceb..b5152018e0 100644
--- a/lib/kernel/src/file.erl
+++ b/lib/kernel/src/file.erl
@@ -95,7 +95,8 @@
Delay :: non_neg_integer()}
| 'delayed_write' | {'read_ahead', Size :: pos_integer()}
| 'read_ahead' | 'compressed'
- | {'encoding', unicode:encoding()}.
+ | {'encoding', unicode:encoding()}
+ | sync.
-type deep_list() :: [char() | atom() | deep_list()].
-type name() :: string() | atom() | deep_list().
-type name_all() :: string() | atom() | deep_list() | (RawFilename :: binary()).
diff --git a/lib/kernel/test/file_SUITE.erl b/lib/kernel/test/file_SUITE.erl
index e4c8f0ffaf..c75639ae7e 100644
--- a/lib/kernel/test/file_SUITE.erl
+++ b/lib/kernel/test/file_SUITE.erl
@@ -805,6 +805,20 @@ new_modes(Config) when is_list(Config) ->
?line {ok, [$\[]} = ?FILE_MODULE:read(Fd6, 1),
?line ok = ?FILE_MODULE:close(Fd6),
+ %% write and sync
+ case ?FILE_MODULE:open(Name1, [write, sync]) of
+ {ok, Fd7} ->
+ ok = io:write(Fd7, Marker),
+ ok = io:put_chars(Fd7, ".\n"),
+ ok = ?FILE_MODULE:close(Fd7),
+ {ok, Fd8} = ?FILE_MODULE:open(Name1, [read]),
+ {ok, Marker} = io:read(Fd8, prompt),
+ ok = ?FILE_MODULE:close(Fd8);
+ {error, enotsup} ->
+ %% for platforms that don't support the sync option
+ ok
+ end,
+
?line [] = flush(),
?line test_server:timetrap_cancel(Dog),
ok.