filehandle.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.\" ========================================================================
.\"
.IX Title "FileHandle 3"
.TH FileHandle 3 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
FileHandle \- supply object methods for filehandles
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use FileHandle;
\&
\&    $fh = new FileHandle;
\&    if ($fh\->open("< file")) {
\&        print <$fh>;
\&        $fh\->close;
\&    }
\&
\&    $fh = new FileHandle "> FOO";
\&    if (defined $fh) {
\&        print $fh "bar\en";
\&        $fh\->close;
\&    }
\&
\&    $fh = new FileHandle "file", "r";
\&    if (defined $fh) {
\&        print <$fh>;
\&        undef $fh;       # automatically closes the file
\&    }
\&
\&    $fh = new FileHandle "file", O_WRONLY|O_APPEND;
\&    if (defined $fh) {
\&        print $fh "corge\en";
\&        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;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\s-1NOTE:\s0 This class is now a front-end to the IO::* classes.
.PP
\&\f(CW\*(C`FileHandle::new\*(C'\fR creates a \f(CW\*(C`FileHandle\*(C'\fR, which is a reference to a
newly created symbol (see the \f(CW\*(C`Symbol\*(C'\fR package).  If it receives any
parameters, they are passed to \f(CW\*(C`FileHandle::open\*(C'\fR; if the open fails,
the \f(CW\*(C`FileHandle\*(C'\fR object is destroyed.  Otherwise, it is returned to
the caller.
.PP
\&\f(CW\*(C`FileHandle::new_from_fd\*(C'\fR creates a \f(CW\*(C`FileHandle\*(C'\fR like \f(CW\*(C`new\*(C'\fR does.
It requires two parameters, which are passed to \f(CW\*(C`FileHandle::fdopen\*(C'\fR;
if the fdopen fails, the \f(CW\*(C`FileHandle\*(C'\fR object is destroyed.
Otherwise, it is returned to the caller.
.PP
\&\f(CW\*(C`FileHandle::open\*(C'\fR accepts one parameter or two.  With one parameter,
it is just a front end for the built-in \f(CW\*(C`open\*(C'\fR 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.
.PP
If \f(CW\*(C`FileHandle::open\*(C'\fR receives a Perl mode string (\*(L">\*(R", \*(L"+<\*(R", etc.)
or a \s-1POSIX\s0 \fIfopen()\fR mode string (\*(L"w\*(R", \*(L"r+\*(R", etc.), it uses the basic
Perl \f(CW\*(C`open\*(C'\fR operator.
.PP
If \f(CW\*(C`FileHandle::open\*(C'\fR is given a numeric mode, it passes that mode
and the optional permissions value to the Perl \f(CW\*(C`sysopen\*(C'\fR operator.
For convenience, \f(CW\*(C`FileHandle::import\*(C'\fR 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.
.PP
\&\f(CW\*(C`FileHandle::fdopen\*(C'\fR is like \f(CW\*(C`open\*(C'\fR except that its first parameter
is not a filename but rather a file handle name, a FileHandle object,
or a file descriptor number.
.PP
If the C functions \fIfgetpos()\fR and \fIfsetpos()\fR are available, then
\&\f(CW\*(C`FileHandle::getpos\*(C'\fR returns an opaque value that represents the
current position of the FileHandle, and \f(CW\*(C`FileHandle::setpos\*(C'\fR uses
that value to return to a previously visited position.
.PP
If the C function \fIsetvbuf()\fR is available, then \f(CW\*(C`FileHandle::setvbuf\*(C'\fR
sets the buffering policy for the FileHandle.  The calling sequence
for the Perl function is the same as its C counterpart, including the
macros \f(CW\*(C`_IOFBF\*(C'\fR, \f(CW\*(C`_IOLBF\*(C'\fR, and \f(CW\*(C`_IONBF\*(C'\fR, except that the buffer
parameter specifies a scalar variable to use as a buffer.  \s-1WARNING:\s0 A
variable used as a buffer by \f(CW\*(C`FileHandle::setvbuf\*(C'\fR must not be
modified in any way until the FileHandle is closed or until
\&\f(CW\*(C`FileHandle::setvbuf\*(C'\fR is called again, or memory corruption may
result!
.PP
See perlfunc for complete descriptions of each of the following
supported \f(CW\*(C`FileHandle\*(C'\fR methods, which are just front ends for the
corresponding built-in functions:
.PP
.Vb 8
\&    close
\&    fileno
\&    getc
\&    gets
\&    eof
\&    clearerr
\&    seek
\&    tell
.Ve
.PP
See perlvar for complete descriptions of each of the following
supported \f(CW\*(C`FileHandle\*(C'\fR methods:
.PP
.Vb 12
\&    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
.Ve
.PP
Furthermore, for doing normal I/O you might need these:
.ie n .IP "$fh\->print" 4
.el .IP "\f(CW$fh\fR\->print" 4
.IX Item "$fh->print"
See \*(L"print\*(R" in perlfunc.
.ie n .IP "$fh\->printf" 4
.el .IP "\f(CW$fh\fR\->printf" 4
.IX Item "$fh->printf"
See \*(L"printf\*(R" in perlfunc.
.ie n .IP "$fh\->getline" 4
.el .IP "\f(CW$fh\fR\->getline" 4
.IX Item "$fh->getline"
This works like <$fh> described in \*(L"I/O Operators\*(R" in perlop
except that it's more readable and can be safely called in a
list context but still returns just one line.
.ie n .IP "$fh\->getlines" 4
.el .IP "\f(CW$fh\fR\->getlines" 4
.IX Item "$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 \fIcroak()\fR if accidentally called in a scalar context.
.PP
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.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
The \fB\s-1IO\s0\fR extension,
perlfunc, 
\&\*(L"I/O Operators\*(R" in perlop.