


lib::IO::Handle(3Perl Programmers Reference Gulib::IO::Handle(3p)


NAME
       IO::Handle - supply object methods for I/O handles

SYNOPSIS
           use IO::Handle;

           $fh = new IO::Handle;
           if ($fh->fdopen(fileno(STDIN),"r")) {
               print $fh->getline;
               $fh->close;
           }

           $fh = new IO::Handle;
           if ($fh->fdopen(fileno(STDOUT),"w")) {
               $fh->print("Some text\n");
           }

           use IO::Handle '_IOLBF';
           $fh->setvbuf($buffer_var, _IOLBF, 1024);

           undef $fh;       # automatically closes the file if it's open

           autoflush STDOUT 1;


DESCRIPTION
       IO::Handle is the base class for all other IO handle
       classes. It is not intended that objects of IO::Handle
       would be created directly, but instead IO::Handle is
       inherited from by several other classes in the IO
       hierarchy.

       If you are reading this documentation, looking for a
       replacement for the FileHandle package, then I suggest you
       read the documentation for IO::File

       A IO::Handle object is a reference to a symbol (see the
       Symbol package)

CONSTRUCTOR
       new ()
           Creates a new IO::Handle object.

       new_from_fd ( FD, MODE )
           Creates a IO::Handle like new does.  It requires two
           parameters, which are passed to the method fdopen; if
           the fdopen fails, the object is destroyed. Otherwise,
           it is returned to the caller.

METHODS
       See the perlfunc manpage for complete descriptions of each
       of the following supported IO::Handle methods, which are
       just front ends for the corresponding built-in functions:




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lib::IO::Handle(3Perl Programmers Reference Gulib::IO::Handle(3p)


           close
           fileno
           getc
           eof
           read
           truncate
           stat
           print
           printf
           sysread
           syswrite

       See the perlvar manpage for complete descriptions of each
       of the following supported IO::Handle methods:

           autoflush
           output_field_separator
           output_record_separator
           input_record_separator
           input_line_number
           format_page_number
           format_lines_per_page
           format_lines_left
           format_name
           format_top_name
           format_line_break_characters
           format_formfeed
           format_write

       Furthermore, for doing normal I/O you might need these:

       $fh->fdopen ( FD, MODE )
            fdopen is like an ordinary open except that its first
            parameter is not a filename but rather a file handle
            name, a IO::Handle object, or a file descriptor
            number.

       $fh->opened
            Returns true if the object is currently a valid file
            descriptor.

       $fh->getline
            This works like <$fh> described in the section on I/O
            Operators in the perlop manpage except that it's more
            readable and can be safely called in an array context
            but still returns just one line.

       $fh->getlines
            This works like <$fh> when called in an array context
            to read all the remaining lines in a file, except
            that it's more readable.  It will also croak() if
            accidentally called in a scalar context.





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lib::IO::Handle(3Perl Programmers Reference Gulib::IO::Handle(3p)


       $fh->ungetc ( ORD )
            Pushes a character with the given ordinal value back
            onto the given handle's input stream.

       $fh->write ( BUF, LEN [, OFFSET }\] )
            This write is like write found in C, that is it is
            the opposite of read. The wrapper for the perl write
            function is called format_write.

       $fh->flush
            Flush the given handle's buffer.

       $fh->error
            Returns a true value if the given handle has
            experienced any errors since it was opened or since
            the last call to clearerr.

       $fh->clearerr
            Clear the given handle's error indicator.

       If the C functions setbuf() and/or setvbuf() are
       available, then IO::Handle::setbuf and IO::Handle::setvbuf
       set the buffering policy for an IO::Handle.  The calling
       sequences for the Perl functions are the same as their C
       counterparts--including the constants _IOFBF, _IOLBF, and
       _IONBF for setvbuf()--except that the buffer parameter
       specifies a scalar variable to use as a buffer.  WARNING:
       A variable used as a buffer by setbuf or setvbuf must not
       be modified in any way until the IO::Handle is closed or
       setbuf or setvbuf is called again, or memory corruption
       may result!  Note that you need to import the constants
       _IOFBF, _IOLBF, and _IONBF explicitly.

       Lastly, there is a special method for working under -T and
       setuid/gid scripts:

       $fh->untaint
            Marks the object as taint-clean, and as such data
            read from it will also be considered taint-clean.
            Note that this is a very trusting action to take, and
            appropriate consideration for the data source and
            potential vulnerability should be kept in mind.

NOTE
       A IO::Handle object is a GLOB reference. Some modules that
       inherit from IO::Handle may want to keep object related
       variables in the hash table part of the GLOB. In an
       attempt to prevent modules trampling on each other I
       propose the that any such module should prefix its
       variables with its own name separated by _'s. For example
       the IO::Socket module keeps a timeout variable in
       'io_socket_timeout'.





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lib::IO::Handle(3Perl Programmers Reference Gulib::IO::Handle(3p)


SEE ALSO
       the perlfunc manpage, the section on I/O Operators in the
       perlop manpage, the IO::File manpage

BUGS
       Due to backwards compatibility, all filehandles resemble
       objects of class IO::Handle, or actually classes derived
       from that class.  They actually aren't.  Which means you
       can't derive your own class from IO::Handle and inherit
       those methods.

HISTORY
       Derived from FileHandle.pm by Graham Barr
       <bodg@tiuk.ti.com>











































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