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.IX Title "Fmode 3pm"
.TH Fmode 3pm 2024-01-10 "perl v5.38.2" "User Contributed Perl Documentation"
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.SH NAME
FileHandle::Fmode \- determine whether a filehandle is opened for reading, writing, or both.
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 6
\& use FileHandle::Fmode qw(:all);
\& .
\& .
\& #$fh and FH are open filehandles
\& print is_R($fh), "\en";
\& print is_W(\e*FH), "\en";
.Ve
.SH FUNCTIONS
.IX Header "FUNCTIONS"
.Vb 5
\& $bool = is_FH($fh);
\& $bool = is_FH(\e*FH);
\&  This is just a (more intuitively named) alias for is_arg_ok().
\&  Returns 1 if its argument is an open filehandle.
\&  Returns 0 if its argument is something other than an open filehandle.
\&
\& $bool = is_arg_ok($fh);
\& $bool = is_arg_ok(\e*FH);
\&  Returns 1 if its argument is an open filehandle.
\&  Returns 0 if its argument is something other than an open filehandle.
\&
\& Arguments to the following functions  must be open filehandles. If
\& any of those functions receive an argument that is not an open
\& filehandle then the function dies with an appropriate error message.
\& To ensure that your script won\*(Aqt suffer such a death, you could first
\& check by passing the argument to is_FH(). Or you could wrap the
\& function call in an eval{} block.
\&
\& Note that it may be possible that a filehandle opened for writing may
\& become unwritable \- if (eg) the disk becomes full. I don\*(Aqt know how
\& the below functions would be affected by such an event. I suspect
\& that they would be unaware of the change ... but I haven\*(Aqt actually
\& checked.
\&
\& $bool = is_R($fh);
\& $bool = is_R(\e*FH);
\&  Returns true if the filehandle is readable.
\&  Else returns false.
\&
\& $bool = is_W($fh);
\& $bool = is_W(\e*FH);
\&  Returns true if the filehandle is writable.
\&  Else returns false
\&
\& $bool = is_RO($fh);
\& $bool = is_RO(\e*FH);
\&  Returns true if the filehandle is readable but not writable.
\&  Else returns false
\&
\& $bool = is_WO($fh);
\& $bool = is_WO(\e*FH);
\&  Returns true if the filehandle is writable but not readable.
\&  Else returns false
\&
\& $bool = is_RW($fh);
\& $bool = is_RW(\e*FH);
\&  Returns true if the filehandle is both readable and writable.
\&  Else returns false
\&
\& $bool = is_A($fh);
\& $bool = is_A(\e*FH);
\&
\&  Returns true if the filehandle was opened for appending.
\&  Else returns false.
\&  Not currently implemented on Win32 with pre\-5.6.1 versions of perl (and
\&  dies with appropriate error message if called on such a platform).
.Ve
.SH CREDITS
.IX Header "CREDITS"
.Vb 4
\& Inspired (hmmm ... is that the right word ?) by an idea from BrowserUK
\& posted on PerlMonks in response to a question from dragonchild. Win32
\& code (including XS code) provided by BrowserUK. Zaxo presented the idea
\& of using fcntl() in an earlier PerlMonks thread.
\&
\& Thanks to dragonchild and BrowserUK for steering this module in
\& the right direction.
\&
\& Thanks to attn.steven.kuo for directing me to the perliol routines
\& that enable us to query filehandles attached to memory objects.
\&
\& And thanks to Jost Krieger for helping to sort out the test failures that
\& were occurring on Solaris (and some other operating systems too).
.Ve
.SH TODO
.IX Header "TODO"
.Vb 3
\& I don\*(Aqt know that anyone still runs pre\-5.6.1 perl on Win32. However, if
\& someone likes to tell me how is_A() could be made to work on pre\-5.6.1
\& Win32 perl, I would be quite happy to implement it.
.Ve
.SH LICENSE
.IX Header "LICENSE"
.Vb 3
\& This program is free software; you may redistribute it and/or
\& modify it under the same terms as Perl itself.
\& Copyright 2006\-2008, 2009, 2010, 2012 Sisyphus
.Ve
.SH AUTHOR
.IX Header "AUTHOR"
.Vb 1
\& Sisyphus <sisyphus at cpan dot org>
.Ve