# phpman > perldoc > IO::ScalarArray

## NAME
    [IO::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/markdown) - IO:: interface for reading/writing an array of scalars

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

        use [IO::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/markdown);
        @data = ("My mes", "sage:\n");

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

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

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

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

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

        ### Open an anonymous temporary array:
        $AH = new [IO::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/markdown);
        $AH->print("Hi there!");
        print "I printed: ", @{$AH->aref}, "\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 [IO::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/markdown);
        @data = ("My mes", "sage:\n");

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

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

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

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

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

        ### Open an anonymous temporary scalar:
        $AH = new [IO::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/markdown);
        print $AH "Hi there!";
        print "I printed: ", @{$AH->aref}, "\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::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/markdown);

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

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

## 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::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/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) arrays of scalars. Logically,
    an array of scalars defines an in-core "file" whose contents are the concatenation of the
    scalars in the array. The handles created by this class are automatically tiehandle'd (though
    please see "WARNINGS" for information relevant to your Perl version).

    For writing large amounts of data with individual print() statements, this class is likely to be
    more efficient than [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown).

    Basically, this:

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

    Or this:

        my @a;
        $AH = new [IO::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/markdown) \@a;
        print $AH "Hel", "lo, ";           ### non-OO style
        print $AH "world!\n";              ### ditto

    Causes @a to be set to the following array of 3 strings:

        ( "Hel" ,
          "lo, " ,
          "world!\n" )

    See [IO::Scalar](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalar/markdown) and compare with this class.

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

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

        Returns the self object on success, undefined on error.

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

    close
        *Instance method.* Disassociate the array handle from its underlying array. 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. This does a [read(1)](https://www.chedong.com/phpMan.php/man/read/1/markdown),
        which is somewhat costly.

    getline
        *Instance method.* Return the next line, or undef on end of data. 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 array.

        Currently, this always causes a "seek to the end of the array" and generates a new array
        entry. This may change in the future.

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

    write BUF, NBYTES, [OFFSET];
        *Instance method.* Write some bytes into the array.

  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 POS,WHENCE
        *Instance method.* Seek to a given position in the stream. Only a WHENCE of 0 (SEEK_SET) is
        supported.

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

    setpos POS
        *Instance method.* Seek to a given position in the array, using the opaque getpos() value.
        Don't expect this to be a number.

    getpos
        *Instance method.* Return the current position in the array, as an opaque value. Don't
        expect this to be a number.

    aref
        *Instance method.* Return a reference to the underlying array.

## 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::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/markdown) will not work
    prior to 5.005_57. [IO::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/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::ScalarArray](https://www.chedong.com/phpMan.php/perldoc/IO%3A%3AScalarArray/markdown) with an old
    Perl. The remedy is to simply use the OO version; e.g.:

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

## VERSION
    $Id: ScalarArray.pm,v 1.7 2005/02/10 21:21:53 dfs Exp $

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

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

### Other contributors
    Thanks to the following individuals for their invaluable contributions (if I've forgotten or
    misspelled your name, please email me!):

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

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

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

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