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authorMichael Santos <michael.santos@gmail.com>2010-04-30 12:22:11 -0400
committerRaimo Niskanen <raimo@erlang.org>2010-06-04 10:47:56 +0200
commit4bd026cccb2c22279dd9c88e704642c5a65d3c53 (patch)
tree5c801bf9813b575eb302039f78b07b50364b6696 /erts/preloaded
parentcbd1378ee1fde835e55614bac9290b281bafe49a (diff)
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Support opening files in exclusive mode
Add an option that atomically tests for the existence of a file and creates it if the file does not exist, by passing the O_EXCL flag to open() on Unix and CREATE_NEW flag on Windows. Support for O_EXCL varies across platforms and filesystems. {ok, Fd} = file:open("/tmp/foo", [write,exclusive]), {error, eexist} = file:open("/tmp/foo", [write,exclusive]).
Diffstat (limited to 'erts/preloaded')
-rw-r--r--erts/preloaded/src/prim_file.erl5
1 files changed, 4 insertions, 1 deletions
diff --git a/erts/preloaded/src/prim_file.erl b/erts/preloaded/src/prim_file.erl
index 2d177bf80e..7f24889bb2 100644
--- a/erts/preloaded/src/prim_file.erl
+++ b/erts/preloaded/src/prim_file.erl
@@ -116,9 +116,10 @@
-define(EFILE_MODE_READ_WRITE, 3).
-define(EFILE_MODE_APPEND, 4).
-define(EFILE_COMPRESSED, 8).
+-define(EFILE_MODE_EXCL, 16).
%% Use this mask to get just the mode bits to be passed to the driver.
--define(EFILE_MODE_MASK, 15).
+-define(EFILE_MODE_MASK, 31).
%% Seek modes for the driver's seek function.
-define(EFILE_SEEK_SET, 0).
@@ -958,6 +959,8 @@ open_mode([compressed|Rest], Mode, Portopts, Setopts) ->
open_mode([append|Rest], Mode, Portopts, Setopts) ->
open_mode(Rest, Mode bor ?EFILE_MODE_APPEND bor ?EFILE_MODE_WRITE,
Portopts, Setopts);
+open_mode([exclusive|Rest], Mode, Portopts, Setopts) ->
+ open_mode(Rest, Mode bor ?EFILE_MODE_EXCL, Portopts, Setopts);
open_mode([delayed_write|Rest], Mode, Portopts, Setopts) ->
open_mode([{delayed_write, 64*1024, 2000}|Rest], Mode,
Portopts, Setopts);