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| author | Michael Kerrisk <mtk.manpages@gmail.com> | 2014-01-21 07:24:57 +0100 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2014-01-24 11:44:56 +0100 |
| commit | 40398c1ac7f507f2598e6324e2c8fc877c4128cf (patch) | |
| tree | bc3d0b052f40259de2082b0e7a9f06c3b2756a17 /man2/open.2 | |
| parent | 72ac726808b20c03aa53c22616230dbe7bbe2060 (diff) | |
| download | man-pages-40398c1ac7f507f2598e6324e2c8fc877c4128cf.tar.gz | |
open.2: Place O_TMPFILE in alphabetical order
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Diffstat (limited to 'man2/open.2')
| -rw-r--r-- | man2/open.2 | 150 |
1 files changed, 75 insertions, 75 deletions
diff --git a/man2/open.2 b/man2/open.2 index 8186680246..ad0d9ee3eb 100644 --- a/man2/open.2 +++ b/man2/open.2 @@ -289,81 +289,6 @@ The following symbolic constants are provided for 00001 others have execute permission .RE .TP -.BR O_TMPFILE " (since Linux 3.11)" -.\" commit 60545d0d4610b02e55f65d141c95b18ccf855b6e -.\" commit f4e0c30c191f87851c4a53454abb55ee276f4a7e -.\" commit bb458c644a59dbba3a1fe59b27106c5e68e1c4bd -Create an unnamed temporary file. -The -.I pathname -argument specifies a directory; -an unnamed inode will be created in that directory's filesystem. -Anything written to the resulting file will be lost when -the last file descriptor is closed, unless the file is given a name. - -.B O_TMPFILE -must be specified with one of -.B O_RDWR -or -.B O_WRONLY -and, optionally, -.BR O_EXCL . -If -.B O_EXCL -is not specified, then -.BR linkat (2) -can be used to link the temporary file into the filesystem, making it -permanent, using code like the following: - -.in +4n -.nf -char path[PATH_MAX]; -fd = open("/path/to/dir", O_TMPFILE | O_RDWR, - S_IRUSR | S_IWUSR); -/* File I/O on 'fd'... */ -snprintf(path, PATH_MAX, "/proc/self/fd/%d", fd); -linkat(AT_FDCWD, path, AT_FDCWD, argv[2], - AT_SYMLINK_FOLLOW); -.fi -.in - -In this case, -the -.BR open () -.I mode -argument determines the file permission mode, as with -.BR O_CREAT . - -There are two main use cases for -.\" Inspired by http://lwn.net/Articles/559147/ -.BR O_TMPFILE : -.RS -.IP * 3 -Improved -.BR tmpfile (3) -functionality: race-free creation of temporary files that -(1) are automatically deleted when closed; -(2) can never be reached via any pathname; -(3) are not subject to symlink attacks; and -(4) do not require the caller to devise unique names. -.IP * -Creating a file that is initially invisible, which is then populated -with data and adjusted to have approriate filesystem attributes -.RB ( chown (2), -.BR chmod (2), -.BR fsetxattr (2), -etc.) -before being atomically linked into the filesystem -in a fully formed state (using -.BR linkat (2) -as described above). -.RE -.IP -.B O_TMPFILE -requires support by the underlying filesystem; -.\" As at 3.13, there's support for at least ext2, ext3, ext4 -only a subset of Linux filesystems provide that support. -.TP .BR O_DIRECT " (since Linux 2.4.10)" Try to minimize cache effects of the I/O to and from this file. In general this will degrade performance, but it is useful in @@ -620,6 +545,81 @@ on the resulting file descriptor will block the calling process until the data has been physically written to the underlying hardware. .IR "But see NOTES below" . .TP +.BR O_TMPFILE " (since Linux 3.11)" +.\" commit 60545d0d4610b02e55f65d141c95b18ccf855b6e +.\" commit f4e0c30c191f87851c4a53454abb55ee276f4a7e +.\" commit bb458c644a59dbba3a1fe59b27106c5e68e1c4bd +Create an unnamed temporary file. +The +.I pathname +argument specifies a directory; +an unnamed inode will be created in that directory's filesystem. +Anything written to the resulting file will be lost when +the last file descriptor is closed, unless the file is given a name. + +.B O_TMPFILE +must be specified with one of +.B O_RDWR +or +.B O_WRONLY +and, optionally, +.BR O_EXCL . +If +.B O_EXCL +is not specified, then +.BR linkat (2) +can be used to link the temporary file into the filesystem, making it +permanent, using code like the following: + +.in +4n +.nf +char path[PATH_MAX]; +fd = open("/path/to/dir", O_TMPFILE | O_RDWR, + S_IRUSR | S_IWUSR); +/* File I/O on 'fd'... */ +snprintf(path, PATH_MAX, "/proc/self/fd/%d", fd); +linkat(AT_FDCWD, path, AT_FDCWD, argv[2], + AT_SYMLINK_FOLLOW); +.fi +.in + +In this case, +the +.BR open () +.I mode +argument determines the file permission mode, as with +.BR O_CREAT . + +There are two main use cases for +.\" Inspired by http://lwn.net/Articles/559147/ +.BR O_TMPFILE : +.RS +.IP * 3 +Improved +.BR tmpfile (3) +functionality: race-free creation of temporary files that +(1) are automatically deleted when closed; +(2) can never be reached via any pathname; +(3) are not subject to symlink attacks; and +(4) do not require the caller to devise unique names. +.IP * +Creating a file that is initially invisible, which is then populated +with data and adjusted to have approriate filesystem attributes +.RB ( chown (2), +.BR chmod (2), +.BR fsetxattr (2), +etc.) +before being atomically linked into the filesystem +in a fully formed state (using +.BR linkat (2) +as described above). +.RE +.IP +.B O_TMPFILE +requires support by the underlying filesystem; +.\" As at 3.13, there's support for at least ext2, ext3, ext4 +only a subset of Linux filesystems provide that support. +.TP .B O_TRUNC If the file already exists and is a regular file and the open mode allows writing (i.e., is |