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@node lseek
@section @code{lseek}
@findex lseek
POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9699919799/functions/lseek.html}
Gnulib module: lseek
Portability problems fixed by Gnulib:
@itemize
@item
This function is declared in a different header file (namely, @code{<io.h>})
on some platforms:
MSVC 14.
@item
On platforms where @code{off_t} is a 32-bit type, @code{lseek} does not work
correctly with files larger than 2 GB@. (Cf. @code{AC_SYS_LARGEFILE}.)
@item
This function mistakenly succeeds on pipes on some platforms: mingw, MSVC 14.
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@item
POSIX does not specify which file descriptors support seeking and which don't.
In practice, regular files and block devices support seeking, and ttys, pipes,
and most character devices don't support it.
@item
When the third argument is invalid, POSIX says that @code{lseek} should set
@code{errno} to @code{EINVAL} and return @minus{}1, but in this situation a
@code{SIGSYS} signal is raised on some platforms:
IRIX 6.5.
@item
Some systems do not support @code{SEEK_DATA} and @code{SEEK_HOLE}:
AIX, HP-UX, Microsoft Windows, NetBSD, OpenBSD.
@end itemize
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