# phpman > man > IO::Scalar

## NAME
    [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) - IO:: interface for reading/writing a scalar

## SYNOPSIS
    Perform I/O on strings, using the basic OO interface...

        use 5.005;
        use [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown);
        $data = "My message:\n";

        ### Open a handle on a string, and append to it:
        $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) \$data;
        $SH->print("Hello");
        $SH->print(", world!\nBye now!\n");
        print "The string is now: ", $data, "\n";

        ### Open a handle on a string, read it line-by-line, then close it:
        $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) \$data;
        while (defined($_ = $SH->getline)) {
            print "Got line: $_";
        }
        $SH->close;

        ### Open a handle on a string, and slurp in all the lines:
        $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) \$data;
        print "All lines:\n", $SH->getlines;

        ### Get the current position (either of two ways):
        $pos = $SH->getpos;
        $offset = $SH->tell;

        ### Set the current position (either of two ways):
        $SH->setpos($pos);
        $SH->seek($offset, 0);

        ### Open an anonymous temporary scalar:
        $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown);
        $SH->print("Hi there!");
        print "I printed: ", ${$SH->sref}, "\n";      ### get at value

    Don't like OO for your I/O? No problem. Thanks to the magic of an invisible tie(), the following
    now works out of the box, just as it does with [IO::Handle](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AHandle/markdown):

        use 5.005;
        use [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown);
        $data = "My message:\n";

        ### Open a handle on a string, and append to it:
        $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) \$data;
        print $SH "Hello";
        print $SH ", world!\nBye now!\n";
        print "The string is now: ", $data, "\n";

        ### Open a handle on a string, read it line-by-line, then close it:
        $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) \$data;
        while (<$SH>) {
            print "Got line: $_";
        }
        close $SH;

        ### Open a handle on a string, and slurp in all the lines:
        $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) \$data;
        print "All lines:\n", <$SH>;

        ### Get the current position (WARNING: requires 5.6):
        $offset = tell $SH;

        ### Set the current position (WARNING: requires 5.6):
        seek $SH, $offset, 0;

        ### Open an anonymous temporary scalar:
        $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown);
        print $SH "Hi there!";
        print "I printed: ", ${$SH->sref}, "\n";      ### get at value

    And for you folks with 1.x code out there: the old tie() style still works, though this is
    *unnecessary and deprecated*:

        use [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown);

        ### Writing to a scalar...
        my $s;
        tie *OUT, '[IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown)', \$s;
        print OUT "line 1\nline 2\n", "line 3\n";
        print "String is now: $s\n"

        ### Reading and writing an anonymous scalar...
        tie *OUT, '[IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown)';
        print OUT "line 1\nline 2\n", "line 3\n";
        tied(OUT)->seek(0,0);
        while (<OUT>) {
            print "Got line: ", $_;
        }

    Stringification works, too!

        my $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) \$data;
        print $SH "Hello, ";
        print $SH "world!";
        print "I printed: $SH\n";

## DESCRIPTION
    This class is part of the [IO::Stringy](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AStringy/markdown) distribution; see [IO::Stringy](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AStringy/markdown) for change log and general
    information.

    The [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) class implements objects which behave just like [IO::Handle](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AHandle/markdown) (or FileHandle)
    objects, except that you may use them to write to (or read from) scalars. These handles are
    automatically tiehandle'd (though please see "WARNINGS" for information relevant to your Perl
    version).

    Basically, this:

        my $s;
        $SH = new [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) \$s;
        $SH->print("Hel", "lo, ");         ### OO style
        $SH->print("world!\n");            ### ditto

    Or this:

        my $s;
        $SH = tie *OUT, '[IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown)', \$s;
        print OUT "Hel", "lo, ";           ### non-OO style
        print OUT "world!\n";              ### ditto

    Causes $s to be set to:

        "Hello, world!\n"

## PUBLIC INTERFACE
### Construction
    new [ARGS...]
        *Class method.* Return a new, unattached scalar handle. If any arguments are given, they're
        sent to open().

    open [SCALARREF]
        *Instance method.* Open the scalar handle on a new scalar, pointed to by SCALARREF. If no
        SCALARREF is given, a "private" scalar is created to hold the file data.

        Returns the self object on success, undefined on error.

    opened
        *Instance method.* Is the scalar handle opened on something?

    close
        *Instance method.* Disassociate the scalar handle from its underlying scalar. Done
        automatically on destroy.

### Input and output
    flush
        *Instance method.* No-op, provided for OO compatibility.

    fileno
        *Instance method.* No-op, returns undef

    getc
        *Instance method.* Return the next character, or undef if none remain.

    getline
        *Instance method.* Return the next line, or undef on end of string. Can safely be called in
        an array context. Currently, lines are delimited by "\n".

    getlines
        *Instance method.* Get all remaining lines. It will croak() if accidentally called in a
        scalar context.

    print ARGS...
        *Instance method.* Print ARGS to the underlying scalar.

        Warning: this continues to always cause a seek to the end of the string, but if you perform
        seek()s and tell()s, it is still safer to explicitly seek-to-end before subsequent print()s.

    read BUF, NBYTES, [OFFSET]
        *Instance method.* Read some bytes from the scalar. Returns the number of bytes actually
        read, 0 on end-of-file, undef on error.

    write BUF, NBYTES, [OFFSET]
        *Instance method.* Write some bytes to the scalar.

    sysread BUF, LEN, [OFFSET]
        *Instance method.* Read some bytes from the scalar. Returns the number of bytes actually
        read, 0 on end-of-file, undef on error.

    syswrite BUF, NBYTES, [OFFSET]
        *Instance method.* Write some bytes to the scalar.

  Seeking/telling and other attributes
    autoflush
        *Instance method.* No-op, provided for OO compatibility.

    binmode
        *Instance method.* No-op, provided for OO compatibility.

    clearerr
        *Instance method.* Clear the error and EOF flags. A no-op.

    eof *Instance method.* Are we at end of file?

    seek OFFSET, WHENCE
        *Instance method.* Seek to a given position in the stream.

    sysseek OFFSET, WHENCE
        *Instance method.* Identical to "seek OFFSET, WHENCE", *q.v.*

    tell
        *Instance method.* Return the current position in the stream, as a numeric offset.

    setpos POS
        *Instance method.* Set the current position, using the opaque value returned by "getpos()".

    getpos
        *Instance method.* Return the current position in the string, as an opaque object.

    sref
        *Instance method.* Return a reference to the underlying scalar.

## WARNINGS
    Perl's TIEHANDLE spec was incomplete prior to 5.005_57; it was missing support for "seek()",
    "tell()", and "eof()". Attempting to use these functions with an [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) will not work prior
    to 5.005_57. [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) will not have the relevant methods invoked; and even worse, this kind of
    bug can lie dormant for a while. If you turn warnings on (via $^W or "perl -w"), and you see
    something like this...

        attempt to seek on unopened filehandle

    ...then you are probably trying to use one of these functions on an [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) with an old Perl.
    The remedy is to simply use the OO version; e.g.:

        $SH->seek(0,0);    ### GOOD: will work on any 5.005
        seek($SH,0,0);     ### WARNING: will only work on 5.005_57 and beyond

## VERSION
    $Id: Scalar.pm,v 1.6 2005/02/10 21:21:53 dfs Exp $

## AUTHORS
### Primary Maintainer
    Dianne Skoll (<dfs@roaringpenguin.com>).

### Principal author
    Eryq (<eryq@zeegee.com>). President, ZeeGee Software Inc (<http://www.zeegee.com>).

### Other contributors
    The full set of contributors always includes the folks mentioned in "CHANGE LOG" in [IO::Stringy](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AStringy/markdown).
    But just the same, special thanks to the following individuals for their invaluable
    contributions (if I've forgotten or misspelled your name, please email me!):

    *Andy Glew,* for contributing "getc()".

    *Brandon Browning,* for suggesting "opened()".

    *David Richter,* for finding and fixing the bug in "PRINTF()".

    *Eric L. Brine,* for his offset-using read() and write() implementations.

    *Richard Jones,* for his patches to massively improve the performance of "getline()" and add
    "sysread" and "syswrite".

    *B. K. Oxley (binkley),* for stringification and inheritance improvements, and sundry good
    ideas.

    *Doug Wilson,* for the [IO::Handle](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AHandle/markdown) inheritance and automatic tie-ing.

## SEE ALSO
    [IO::String](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AString/markdown), which is quite similar but which was designed more-recently and with an
    [IO::Handle](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AHandle/markdown)-like interface in mind, so you could mix OO- and native-filehandle usage without
    using tied().

    *Note:* as of version 2.x, these classes all work like their [IO::Handle](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AHandle/markdown) counterparts, so we have
    comparable functionality to [IO::String](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AString/markdown).