Section: Linux Programmer's Manual (2)
sync, syncfs - commit filesystem caches to disk
int syncfs(int fd);
Feature Test Macro Requirements for glibc (see
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE
causes all pending modifications to filesystem metadata and cached file
data to be written to the underlying filesystems.
but synchronizes just the filesystem containing file
referred to by the open file descriptor
returns 0 on success;
on error, it returns -1 and sets
to indicate the error.
is always successful.
can fail for at least the following reasons:
is not a valid file descriptor.
An error occurred during synchronization.
This error may relate to data written to any file on the filesystem, or on
metadata related to the filesystem itself.
Disk space was exhausted while synchronizing.
- ENOSPC, EDQUOT
Data was written to a files on NFS or another filesystem which does not
allocate space at the time of a
system call, and some previous write failed due to insufficient
first appeared in Linux 2.6.39;
library support was added to glibc in version 2.14.
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
Since glibc 2.2.2, the Linux prototype for
is as listed above,
following the various standards.
In glibc 2.2.1 and earlier,
it was "int sync(void)", and
always returned 0.
According to the standard specification (e.g., POSIX.1-2001),
schedules the writes, but may return before the actual
writing is done.
However Linux waits for I/O completions,
provide the same guarantees as
called on every file in
the system or filesystem respectively.
In mainline kernel versions prior to 5.8,
will fail only when passed a bad file descriptor
Since Linux 5.8,
will also report an error if one or more inodes failed
to be written back since the last
Before version 1.3.20 Linux did not wait for I/O to complete
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