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| -rw-r--r-- | ChangeLog | 4 | ||||
| -rw-r--r-- | manual/llio.texi | 28 |
2 files changed, 32 insertions, 0 deletions
@@ -1,3 +1,7 @@ +2017-11-04 Florian Weimer <fweimer@redhat.com> + + * manual/llio.texi (Open-time Flags): Document O_TMPFILE. + 2017-11-03 Joseph Myers <joseph@codesourcery.com> * math/math.h [__HAVE_DISTINCT_FLOAT16 diff --git a/manual/llio.texi b/manual/llio.texi index e72c53c..10ad546 100644 --- a/manual/llio.texi +++ b/manual/llio.texi @@ -3478,6 +3478,34 @@ If set, the file will be created if it doesn't already exist. If both @code{O_CREAT} and @code{O_EXCL} are set, then @code{open} fails if the specified file already exists. This is guaranteed to never clobber an existing file. + +The @code{O_EXCL} flag has a special meaning in combination with +@code{O_TMPFILE}; see below. +@end deftypevr + +@deftypevr Macro int O_TMPFILE +@standards{GNU, fcntl.h} +If this flag is specified, functions in the @code{open} family create an +unnamed temporary file. In this case, the pathname argument to the +@code{open} family of functions (@pxref{Opening and Closing Files}) is +interpreted as the directory in which the temporary file is created +(thus determining the file system which provides the storage for the +file). The @code{O_TMPFILE} flag must be combined with @code{O_WRONLY} +or @code{O_RDWR}, and the @var{mode} argument is required. + +The temporary file can later be given a name using @code{linkat}, +turning it into a regular file. This allows the atomic creation of a +file with the specific file attributes (mode and extended attributes) +and file contents. If, for security reasons, it is not desirable that a +name can be given to the file, the @code{O_EXCL} flag can be specified +along with @code{O_TMPFILE}. + +Not all kernels support this open flag. If this flag is unsupported, an +attempt to create an unnamed temporary file fails with an error of +@code{EINVAL}. If the underlying file system does not support the +@code{O_TMPFILE} flag, an @code{EOPNOTSUPP} error is the result. + +The @code{O_TMPFILE} flag is a GNU extension. @end deftypevr @deftypevr Macro int O_NONBLOCK |