From 4bd026cccb2c22279dd9c88e704642c5a65d3c53 Mon Sep 17 00:00:00 2001 From: Michael Santos Date: Fri, 30 Apr 2010 12:22:11 -0400 Subject: 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]). --- erts/preloaded/src/prim_file.erl | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'erts/preloaded/src') 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); -- cgit v1.2.3