# phpman > info > IO::Scalar

IO::[Scalar(3pm)](https://www.chedong.com/phpMan.php/man/Scalar/3pm/markdown)       User Contributed Perl Documentation      IO::[Scalar(3pm)](https://www.chedong.com/phpMan.php/man/Scalar/3pm/markdown)

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).

perl v5.28.1                      2019-02-28                   IO::[Scalar(3pm)](https://www.chedong.com/phpMan.php/man/Scalar/3pm/markdown)