1LSEEK64(3)                 Linux Programmer's Manual                LSEEK64(3)
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NAME

6       lseek64 - reposition 64-bit read/write file offset
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SYNOPSIS

9       #define _LARGEFILE64_SOURCE     /* See feature_test_macros(7) */
10       #include <sys/types.h>
11       #include <unistd.h>
12
13       off64_t lseek64(int fd, off64_t offset, int whence);
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DESCRIPTION

16       The lseek(2) family of functions reposition the offset of the open file
17       associated with the file descriptor fd to offset bytes relative to  the
18       start,  current position, or end of the file, when whence has the value
19       SEEK_SET, SEEK_CUR, or SEEK_END, respectively.
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21       For more details, return value, and errors, see lseek(2).
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23       Four interfaces are  available:  lseek(2),  lseek64(),  llseek(2),  and
24       _llseek(2).
25
26   lseek()
27       Prototype:
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29           off_t lseek(int fd, off_t offset, int whence);
30
31       lseek(2)  uses  the type off_t.  This is a 32-bit signed type on 32-bit
32       architectures, unless one compiles with
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34           #define _FILE_OFFSET_BITS 64
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36       in which case it is a 64-bit signed type.
37
38   lseek64()
39       Prototype:
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41           off64_t lseek64(int fd, off64_t offset, int whence);
42
43       The library routine lseek64() uses a 64-bit type even when off_t  is  a
44       32-bit  type.   Its  prototype (and the type off64_t) is available only
45       when one compiles with
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47           #define _LARGEFILE64_SOURCE
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49       The function lseek64() is available since glibc 2.1, and is defined  to
50       be an alias for llseek().
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52   llseek()
53       Prototype:
54
55           loff_t llseek(int fd, loff_t offset, int whence);
56
57       The  type loff_t is a 64-bit signed type.  The library routine llseek()
58       is available in glibc and works without special defines.  However,  the
59       glibc  headers  do not provide a prototype.  Users should add the above
60       prototype, or something equivalent, to their own  source.   When  users
61       complained  about  data  loss  caused by a miscompilation of e2fsck(8),
62       glibc 2.1.3 added the link-time warning
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64           "the `llseek´ function may be dangerous; use `lseek64´ instead."
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66       This makes this function unusable if one desires a warning-free  compi‐
67       lation.
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69   _llseek()
70       On 32-bit architectures, this is the system call that is used to imple‐
71       ment all of the above functions.  The prototype is:
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73           int _llseek(int fd, off_t offset_hi, off_t offset_lo,
74                       loff_t *result, int whence);
75
76       For more details, see llseek(2).
77
78       64-bit systems don't need an _llseek() system call.  Instead, they have
79       an lseek(2) system call that supports 64-bit file offsets.
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ATTRIBUTES

82       For   an   explanation   of   the  terms  used  in  this  section,  see
83       attributes(7).
84
85       ┌──────────┬───────────────┬─────────┐
86       │Interface │ Attribute     │ Value   │
87       ├──────────┼───────────────┼─────────┤
88       │lseek64() │ Thread safety │ MT-Safe │
89       └──────────┴───────────────┴─────────┘

SEE ALSO

91       llseek(2), lseek(2)
92

COLOPHON

94       This page is part of release 5.02 of the Linux  man-pages  project.   A
95       description  of  the project, information about reporting bugs, and the
96       latest    version    of    this    page,    can     be     found     at
97       https://www.kernel.org/doc/man-pages/.
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101Linux                             2017-09-15                        LSEEK64(3)