Section (3) lseek64
lseek64 — reposition 64-bit read/write file offset
#define _LARGEFILE64_SOURCE /* See feature_test_macros(7) */ #include <sys/types.h> #include <unistd.h>
The lseek(2) family of
functions reposition the offset of the open file associated
with the file descriptor
offset bytes relative to the
start, current position, or end of the file, when
whence has the value
For more details, return value, and errors, see lseek(2).
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.
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
available since glibc 2.1, and is defined to be an alias
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 compilation.
On 32-bit architectures, this is the system call that is used to implement all of the above functions. The prototype is:
For more details, see llseek(2).
64-bit systems don_zsingle_quotesz_t need an
_llseek() system call. Instead, they have
an lseek(2) system call that
supports 64-bit file offsets.
For an explanation of the terms used in this section, see attributes(7).
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Copyright 2004 Andries Brouwer <aebcwi.nl>.
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