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SYNC

Section: Linux Programmer's Manual (2)
Updated: 2011-09-07
Index Return to Main Contents

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NAME

sync, syncfs - commit buffer cache to disk  

SYNOPSIS

#include <unistd.h>

void sync(void);

void syncfs(int fd);

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

sync():

_BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

syncfs():

_GNU_SOURCE

 

DESCRIPTION

sync() causes all buffered modifications to file metadata and data to be written to the underlying file systems.

syncfs() is like sync(), but synchronizes just the file system 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.  

CONFORMING TO

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

syncfs() is Linux-specific.  

NOTES

Since glibc 2.2.2 the Linux prototype for sync() is as listed above, following the various standards. In libc4, libc5, and glibc up to 2.2.1 it was "int sync(void)", and sync() always returned 0.  

BUGS

According to the standard specification (e.g., POSIX.1-2001), sync() schedules the writes, but may return before the actual writing is done. However, since version 1.3.20 Linux does actually wait. (This still does not guarantee data integrity: modern disks have large caches.)  

SEE ALSO

bdflush(2), fdatasync(2), fsync(2), sync(8), update(8)  

COLOPHON

This page is part of release 3.35 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/man-pages/.

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Index

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

VERSIONS

CONFORMING TO

NOTES

BUGS

SEE ALSO

COLOPHON

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