@node freopen
@subsection @code{freopen}
@findex freopen

POSIX specification:@* @url{https://pubs.opengroup.org/onlinepubs/9799919799/functions/freopen.html}

Gnulib module: freopen
@mindex freopen

Portability problems fixed by Gnulib:
@itemize
@item
On some platforms, if @code{stream} does not already have an open
file descriptor, @code{freopen} returns the stream without opening
the file: glibc 2.24.
@item
On platforms where @code{off_t} is a 32-bit type, @code{freopen} may not work
correctly with files 2 GiB and larger.  @xref{Large File Support}.
@item
On Windows platforms (excluding Cygwin), this function does usually not
recognize the @file{/dev/null} filename.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
On Windows platforms (excluding Cygwin), this function does not set @code{errno}
upon failure.
@item
This function does not support a @code{NULL} file name argument on some
platforms:
OpenBSD 4.9, AIX 7.1, HP-UX 11.23, Solaris 10, mingw, MSVC 14.
@item
This function does not fail when the file name argument ends in a slash
and (without the slash) names a nonexistent file or a file that is not a
directory, on some platforms:
HP-UX 11.00, Solaris 9.
@item
Applications should not assume that @code{fileno(f)} will be the same
before and after a call to @code{freopen(name,mode,f)}.
@mindex freopen-safer
However, the
module @code{freopen-safer} can at least protect @code{stdin}, @code{stdout},
and @code{stderr}.
@end itemize
