This will return the open mode for a given Perl filehandle as a number.

• fmode($fh) & 1 and print 'is readonly';
• fmode($fh) & 2 and print 'is writeonly';
• fmode($fh) & 128 and print 'is readwrite';

#! perl -slw
use strict;
use Inline C => 'DATA', NAME => 'fmode', CLEAN_AFTER_BUILD => 0;

open FILE, $ARGV[0] or die "'$ARGV[0]:$!";

printf "%x\n", fmode( \*FILE );


__DATA__
C:\test>fmode "<junk.dat"
1

C:\test>fmode ">junk.dat"
2

C:\test>fmode ">>junk.dat"
2

C:\test>fmode "+<junk.dat"
80

C:\test>fmode "+>junk.dat"
80

C:\test>fmode "+>>junk.dat"
80

__C__
int fmode( FILE *stream ) {
    return stream->_flag;
}
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In theory you could grab the XS code generated by Inline::C and form that into a module (Win32::Fmode?) for distribution--but I've never managed to get that to work. Everytime I've tried, xsubpp bellyaches about being unable to parse stuff:

C:\Perl\bin\perl.exe C:\Perl\lib\ExtUtils/xsubpp  
   -typemap C:\Perl\lib\ExtUtils\typemap  
   Fmode.xs > Fmode.xsc && C:\Perl\bin\perl.exe 
   -MExtUtils::Command -e mv Fmode.xsc Fmode.c

Error: Cannot parse function definition from 
'fmode( FILE *stream ) {' in Fmode.xs, line 12
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And since none {{censored}} ....