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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       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at https://www.kernel.org/doc/man-pages/.