1SYNC(2)                    Linux Programmer's Manual                   SYNC(2)
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NAME

6       sync, syncfs - commit filesystem caches to disk
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SYNOPSIS

9       #include <unistd.h>
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11       void sync(void);
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13       int syncfs(int fd);
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15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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17       sync():
18           _XOPEN_SOURCE >= 500
19               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
20               || /* Glibc versions <= 2.19: */ _BSD_SOURCE
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22       syncfs():
23           _GNU_SOURCE
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DESCRIPTION

26       sync()  causes  all  pending  modifications  to filesystem metadata and
27       cached file data to be written to the underlying filesystems.
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29       syncfs() is like sync(), but synchronizes just the filesystem  contain‐
30       ing file referred to by the open file descriptor fd.
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RETURN VALUE

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

37       sync() is always successful.
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39       syncfs() can fail for at least the following reason:
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41       EBADF  fd is not a valid file descriptor.
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VERSIONS

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

48       sync(): POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
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50       syncfs() is Linux-specific.
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NOTES

53       Since  glibc  2.2.2, the Linux prototype for sync() is as listed above,
54       following the various standards.  In glibc 2.2.1 and  earlier,  it  was
55       "int sync(void)", and sync() always returned 0.
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57       According  to  the  standard specification (e.g., POSIX.1-2001), sync()
58       schedules the writes, but may return before the actual writing is done.
59       However  Linux  waits  for I/O completions, and thus sync() or syncfs()
60       provide the same guarantees as fsync called on every file in the system
61       or filesystem respectively.
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BUGS

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

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

71       This page is part of release 4.16 of the Linux  man-pages  project.   A
72       description  of  the project, information about reporting bugs, and the
73       latest    version    of    this    page,    can     be     found     at
74       https://www.kernel.org/doc/man-pages/.
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78Linux                             2017-09-15                           SYNC(2)
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