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NAME

       sync, syncfs - commit filesystem caches to disk

SYNOPSIS

       #include <unistd.h>

       void sync(void);

       int syncfs(int fd);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       sync():
           _XOPEN_SOURCE >= 500
               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE

       syncfs():
           _GNU_SOURCE

DESCRIPTION

       sync()  causes all pending modifications to filesystem metadata and cached file data to be written to the
       underlying filesystems.

       syncfs() is like sync(), but synchronizes just the filesystem containing file referred  to  by  the  open
       file descriptor fd.

RETURN VALUE

       syncfs() returns 0 on success; on error, it returns -1 and sets errno to indicate the error.

ERRORS

       sync() is always successful.

       syncfs() can fail for at least the following reason:

       EBADF  fd is not a valid file descriptor.

VERSIONS

       syncfs() first appeared in Linux 2.6.39; library support was added to glibc in version 2.14.

CONFORMING TO

       sync(): POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

       syncfs() is Linux-specific.

NOTES

       Since  glibc  2.2.2,  the Linux prototype for sync() is as listed above, following the various standards.
       In glibc 2.2.1 and earlier, it was "int sync(void)", and sync() always returned 0.

       According to the standard specification (e.g., POSIX.1-2001), sync() schedules the writes, but may return
       before  the actual writing is done.  However Linux waits for I/O completions, and thus sync() or syncfs()
       provide the same guarantees as fsync called on every file in the system or filesystem respectively.

BUGS

       Before version 1.3.20 Linux did not wait for I/O to complete before returning.

SEE ALSO

       sync(1), fdatasync(2), fsync(2)

COLOPHON

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