Страницы справочника OS X

Эта страница руководства является частью версии 5.0 Инструментов XCode

Читать страницы руководства

FileHandle(3pm)                       Perl Programmers Reference Guide                       FileHandle(3pm)



NAME
       FileHandle - supply object methods for filehandles

SYNOPSIS
           use FileHandle;

           $fh = FileHandle->new;
           if ($fh->open("< file")) {
               print <$fh>;
               $fh->close;
           }

           $fh = FileHandle->new("> FOO");
           if (defined $fh) {
               print $fh "bar\n";
               $fh->close;
           }

           $fh = FileHandle->new("file", "r");
           if (defined $fh) {
               print <$fh>;
               undef $fh;       # automatically closes the file
           }

           $fh = FileHandle->new("file", O_WRONLY|O_APPEND);
           if (defined $fh) {
               print $fh "corge\n";
               undef $fh;       # automatically closes the file
           }

           $pos = $fh->getpos;
           $fh->setpos($pos);

           $fh->setvbuf($buffer_var, _IOLBF, 1024);

           ($readfh, $writefh) = FileHandle::pipe;

           autoflush STDOUT 1;

DESCRIPTION
       NOTE: This class is now a front-end to the IO::* classes.

       "FileHandle::new" creates a "FileHandle", which is a reference to a newly created symbol (see the
       "Symbol" package).  If it receives any parameters, they are passed to "FileHandle::open"; if the open
       fails, the "FileHandle" object is destroyed.  Otherwise, it is returned to the caller.

       "FileHandle::new_from_fd" creates a "FileHandle" like "new" does.  It requires two parameters, which
       are passed to "FileHandle::fdopen"; if the fdopen fails, the "FileHandle" object is destroyed.
       Otherwise, it is returned to the caller.

       "FileHandle::open" accepts one parameter or two.  With one parameter, it is just a front end for the
       built-in "open" function.  With two parameters, the first parameter is a filename that may include
       whitespace or other special characters, and the second parameter is the open mode, optionally
       followed by a file permission value.

       If "FileHandle::open" receives a Perl mode string (">", "+<", etc.)  or a POSIX fopen() mode string
       ("w", "r+", etc.), it uses the basic Perl "open" operator.

       If "FileHandle::open" is given a numeric mode, it passes that mode and the optional permissions value
       to the Perl "sysopen" operator.  For convenience, "FileHandle::import" tries to import the O_XXX
       constants from the Fcntl module.  If dynamic loading is not available, this may fail, but the rest of
       FileHandle will still work.

       "FileHandle::fdopen" is like "open" except that its first parameter is not a filename but rather a
       file handle name, a FileHandle object, or a file descriptor number.

       If the C functions fgetpos() and fsetpos() are available, then "FileHandle::getpos" returns an opaque
       value that represents the current position of the FileHandle, and "FileHandle::setpos" uses that
       value to return to a previously visited position.

       If the C function setvbuf() is available, then "FileHandle::setvbuf" sets the buffering policy for
       the FileHandle.  The calling sequence for the Perl function is the same as its C counterpart,
       including the macros "_IOFBF", "_IOLBF", and "_IONBF", except that the buffer parameter specifies a
       scalar variable to use as a buffer.  WARNING: A variable used as a buffer by "FileHandle::setvbuf"
       must not be modified in any way until the FileHandle is closed or until "FileHandle::setvbuf" is
       called again, or memory corruption may result!

       See perlfunc for complete descriptions of each of the following supported "FileHandle" methods, which
       are just front ends for the corresponding built-in functions:

           close
           fileno
           getc
           gets
           eof
           clearerr
           seek
           tell

       See perlvar for complete descriptions of each of the following supported "FileHandle" 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

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

       $fh->print
           See "print" in perlfunc.

       $fh->printf
           See "printf" in perlfunc.

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

       $fh->getlines
           This works like <$fh> when called in a list 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.

       There are many other functions available since FileHandle is descended from IO::File, IO::Seekable,
       and IO::Handle.  Please see those respective pages for documentation on more functions.

SEE ALSO
       The IO extension, perlfunc, "I/O Operators" in perlop.



perl v5.16.2                                     2012-08-26                                  FileHandle(3pm)