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man:lseek64

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

NAME

     lseek64 - reposition 64-bit read/write file offset

SYNOPSIS

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

DESCRIPTION

     The lseek(2) family of functions reposition the offset of the open file
     associated with the file descriptor fd to offset bytes relative to  the
     start,  current position, or end of the file, when whence has the value
     SEEK_SET, SEEK_CUR, or SEEK_END, respectively.
     For more details, return value, and errors, see lseek(2).
     Four interfaces are  available:  lseek(2),  lseek64(),  llseek(2),  and
     _llseek(2).
 lseek()
     Prototype:
         off_t lseek(int fd, off_t offset, int whence);
     lseek(2)  uses  the type off_t.  This is a 32-bit signed type on 32-bit
     architectures, unless one compiles with
         #define _FILE_OFFSET_BITS 64
     in which case it is a 64-bit signed type.
 lseek64()
     Prototype:
         off64_t lseek64(int fd, off64_t offset, int whence);
     The library routine lseek64() uses a 64-bit type even when off_t  is  a
     32-bit  type.   Its  prototype (and the type off64_t) is available only
     when one compiles with
         #define _LARGEFILE64_SOURCE
     The function lseek64() is available since glibc 2.1, and is defined  to
     be an alias for llseek().
 llseek()
     Prototype:
         loff_t llseek(int fd, loff_t offset, int whence);
     The  type loff_t is a 64-bit signed type.  The library routine llseek()
     is available in glibc and works without special defines.  However,  the
     glibc  headers  do not provide a prototype.  Users should add the above
     prototype, or something equivalent, to their own  source.   When  users
     complained  about  data  loss  caused by a miscompilation of e2fsck(8),
     glibc 2.1.3 added the link-time warning
         "the `llseek' function may be dangerous; use `lseek64' instead."
     This makes this function unusable if one desires a warning-free  compi-
     lation.
 _llseek()
     On 32-bit architectures, this is the system call that is used to imple-
     ment all of the above functions.  The prototype is:
         int  _llseek(int   fd,   off_t   offset_hi,   off_t   offset_lo,
         loff_t *result, int whence);
     For more details, see llseek(2).
     64-bit systems don't need an _llseek() system call.  Instead, they have
     an lseek(2) system call that supports 64-bit file offsets.

ATTRIBUTES

     For  an  explanation  of  the  terms  used   in   this   section,   see
     attributes(7).
     +----------+---------------+---------+
     |Interface | Attribute     | Value   |
     +----------+---------------+---------+
     |lseek64() | Thread safety | MT-Safe |
     +----------+---------------+---------+

SEE ALSO

     llseek(2), lseek(2)

COLOPHON

     This  page  is  part of release 4.16 of the Linux man-pages project.  A
     description of the project, information about reporting bugs,  and  the
     latest     version     of     this    page,    can    be    found    at
     https://www.kernel.org/doc/man-pages/.

Linux 2017-09-15 LSEEK64(3)

/data/webs/external/dokuwiki/data/pages/man/lseek64.txt · Last modified: 2019/05/17 09:47 by 127.0.0.1

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