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PHP RFC: fsync() function
- Version: 1.0
- Date: 2021-01-30
- Author: David Gebler, email@example.com
- Status: Under Discussion
- First Published at: http://wiki.php.net/rfc/fsync_function
fsync() is a function similar to fflush(), however where fflush() only instructs the application to flush its internal buffers out to the OS, fsync() further instructs the OS to flush its buffers to physical storage, ensuring a completed and persisted write before returning any success. PHP provides plain stream wrappers for most common file system functions inherited from C and is indeed one of few major languages to not provide any interface to fsync. This RFC proposes implementing fsync in core.
This RFC would add an fsync() function accepting a single parameter of a stream resource. The implementation of this function would be a thin wrapper around the standard C fsync (or equivalent _commit on Windows API, which uses an identical signature).
The related function fdatasync() which syncs data but not necessarily metadata would also be added, however this is not supported on Windows and the proposal there is to still provide fdatasync() but merely as an alias of fsync(). On POSIX, fdatasync() is properly implemented.
$fp = fopen('file.txt', 'w'); fwrite($fp, 'string'); var_dump(fsync($fp)); bool(true) $fp = fopen('php://memory','w+'); fwrite($fp,"Test line 1\nLine 2\n"); var_dump(fsync($fp)); Warning: fsync(): Can't fsync this stream in php shell code on line 1 bool(false) $fp = fopen('php://stdin', 'w'); var_dump(fsync($fp)); bool(false)
Backward Incompatible Changes
Proposed PHP Version(s)
None, this function would be available in all SAPIs supporting plain stream wrappers.
To Existing Extensions
Proposed Voting Choices
Accept RFC as proposed.