=head1 TITLE
[DRAFT] Synopsis 28 - Special Names [DRAFT]
=head1 AUTHORS
Larry Wall <larry@wall.org>
Tim Nelson <wayland@wayland.id.au>
Lyle Hopkins <webmaster@cosmicperl.com>
Carl Mäsak <cmasak@gmail.com>
=head1 VERSION
Created: 23 Feb 2009, created by Tim Nelson from miscellaneous documents lying around
Last Modified: 17 Nov 2010
Version: 9
=head1 Special Variables
=head2 Introduction
This document serves as a collection point
for what is known about special variables
in Perl 6 and correlates them with the changes from Perl 5.
If you are trying to find the Perl 6 equivalent of a Perl 5 special
variable you know, try searching this file for the Perl 5 version.
Each main entry is followed by a note containing the corresponding
Perl 5 variable(s). The list of main entries is also followed by
a table showing the 5 and 6 variables side-by-side.
=head2 Overview
=head3 Secondary Sigils (also known as "twigils")
A quick reminder of the relevant twigils from S02:
$?foo # Compiler constants (fixed at compile time)
$*foo # Context variable, default global (run time)
$=foo # File-scoped Pod data
The various C<$?foo> variables are determined at compile time, and are
not modifiable at run time. This does not mean that the variable has the
same value everywhere; for instance, C<$?LINE> is different on every line
of the program.
The C<$*foo> variables function both as dynamically scoped variables
and as globals. Globalness is relative, in other words. Any dynamic
scope may modify the set of globals visible via the C<$*foo> notation.
Most of the standard globals listed below actually live either in
the C<PROCESS> or the C<GLOBAL> package, where C<PROCESS> contains
globals belonging to the entire process, while C<GLOBAL> contains the
globals belonging to the current interpreter, since a process may be
running more than one interpreter. Unless otherwise indicated below,
the outermost definition of these variables are kept in the C<PROCESS>
package.
The C<$=foo> variables are related to the C<$?foo> variables
insofar as the text of the program is known at compile time, so the
values are static. However, the different twigil indicates that the
variable contains Pod data, which is primarily under user control
rather than compiler control. The structure of these variables will
be fleshed out in S26.
=head3 Named variables
Variable Spec Type Description
-------- ---- ---- -----------
@_ # ??? (FIX)
$! S04 # Current Exception object
$/ S05 Match # Last match
$0, $1, $2 S05 Str # First captured value from match: $/[0]
$?ARCH Application # Host architecture
$?XARCH Application # Target architecture
@*ARGS S06 Array of Str # command-line arguments
$*ARGFILES S02 IO # The magic command-line input handle
&?BLOCK S06 Block # current block (itself)
::?CLASS S12 Str # current class (as package or type name)
$?CLASS S02 Class # current class
@=COMMENT (S26) # All the comment blocks in the file
%?CONFIG Hash of XXX # configuration hash XXX What does this do?
$*CWD Path # current working directory
$=DATA (S26) IO # data block handle (=begin DATA ... =end)
@=DATA (S26) Array # Same as above, but array
%?DEEPMAGIC S13 Hash of XXX # Controls the mappings of magical names to sub definitions
$?DISTRO S02 Application # Which OS distribution am I compiling under
$*DISTRO S02 Application # Which OS distribution am I running under
$*EGID Int # effective group id
%*ENV S02 Hash of Str # system environment variables
$*ERR S16 IO # Standard error handle
$*EUID Int # effective user id
$*EXECUTABLE_NAME Str # executable name
$?FILE S02 Str # current filename of source file
$?GRAMMAR S02 Grammar # current grammar
$*GID Int # group id
$*IN S16 IO # Standard input handle; is an IO object
@*INC S11 # where to search for user modules (but not std lib!)
%?LANG S02 Hash of Grammar # What is the current set of interwoven languages?
$*LANG S02 Str # LANG variable from %*ENV that defines what human language is used
$?LINE S02 Int # current line number in source file
%*META-ARGS S19 Hash of XXX # Meta-arguments
$?MODULE S02 Module # current module
%*OPTS S19 Hash of XXX # Options from command line
%*OPT... S19 Hash of XXX # Options from command line to be passed down
$?KERNEL Application # operating system compiled for
$*KERNEL Application # operating system running under
$*OUT S16 IO # Standard output handle
$?PACKAGE S02 Package # current package
$?PERL S02 Application # Which Perl am I compiled for?
$*PERL S02 Application # perl version running under
$*PID Int # system process id
%=POD S02 # (or some such)
$*PROGRAM_NAME S19 Str # name of the Perl program being executed
%*PROTOCOLS S16 Hash of Method # Stores the methods needed for the uri() function
::?ROLE Str # current role (as package or type name)
$?ROLE S02 Role # current role
&?ROUTINE S06 Routine # current sub or method (itself)
$?SCOPE S02 # Current "my" scope (XXX unnecessary?)
$*TZ S32 # Local time zone
$*UID Int # system user id
$?USAGE S06 Str # Default usage message generated at compile time
$?VM S02 Application # Which virtual machine am I compiling under
$?XVM S02 Application # Which virtual machine am I cross-compiling for
Note that dynamic variables such as C<$*OUT> may have more than
one current definition in the outer dynamic context, in which case
the innermost dynamic scope in which it is defined determines the meaning. For instance,
C<$PROCESS::OUT> is the stdout for the entire process, but each
interpreter can set its own C<$GLOBAL::OUT> to make C<$*OUT> mean
whatever it wants independently of other interpreters. Any dynamic
scope may also declare a local meaning of C<$*OUT> that applies only
to called code. Likewise each thread could log its own errors
to its own C<$*ERR>, since a thread is a dynamic scope.
The class C<Application> collects a few common features of some of the special
variables such as C<$*PERL>, C<$?VM>, C<$*KERNEL>, etc.
class Application {
has Str $.name;
has Str $.auth;
has Version $.version;
}
=head3 Perl5 to Perl6 special variable translation
If a column has a "-" in it, it means that item is unavailable in that version of Perl.
Perl 5 Perl 6 Comment
----------- ----------- -----------------------
STDIN $*IN See S16; actual variable is $PROCESS::IN
STDOUT $*OUT See S16; actual variable is $PROCESS::OUT
STDERR $*ERR See S16; actual variable is $PROCESS::ERR
$_ $ARG $_ More lexically aware
$_[1],$_[2].. $^a,$^b..
$a,$b - Just params to anonymous block
- $/ Object with results of last regex match
$1,$2,$3... $1,$2,$3...
$& $MATCH $<>
$` $PREMATCH substr based on $/.from
$' $POSTMATCH substr based on $/.to
$+ - But info can now be retrieved from $/
$^N $*MOST_RECENT_CAPTURED_MATCH ...or some such.
or $/[*-$n] ...or omit
@- $1.start, etc
@+ $1.end, etc.
%! -
$[ - This feature has been removed
$* - Deprecated long ago
$# - Deprecated long ago
$^H - These were only ever internal anyway
%^H -
- $! Current exception (see L<S04-control>)
$! $ERRNO $OS_ERROR - Use shiny new $!
$? $CHILD_ERROR - Use shiny new $!
$@ $EVAL_ERROR - Use shiny new $!
$^E - Use shiny new $!
$^S -
$. $NR $*IN.input_record_number()
$/ $RS $*IN.input_record_separator()
$| $*OUT.autoflush()
$, $OFS $*OUT.output_field_separator()
$\ $*OUT.output_record_separator()
$" $LIST_SEPARATOR -
$; $SUBSEP -
$$ $PID $*PID
$< $UID $*UID Real UID (User ID)
$( $GID $*GID Real GID (Group ID)
$> $EUID $*EUID Effective UID
$) $EGID $*EGID Effective GID
$0 $PROGRAM_NAME $*PROGRAM_NAME
$^C $COMPILING $*COMPILING
$^D $DEBUGGING $*DEBUGGING
$^F $SYS_FD_MAX $*SYS_FD_MAX ...or some such
$^I $INPLACE_EDIT $*INPLACE_EDIT ...or some such
$^M $*EMERGENCY_MEMORY ...or some such (or omit)
$^O $OSNAME $*OSNAME ...or some such
$^P $PERLDB $*PERLDB ...or some such
$^R $*LAST_REGEXP_CODE_RESULT ...or some such. Or omit.
$^T $BASETIME $*INITTIME A Temporal::Instant object
$^V $] $?PERL.version
$^W $*WARNINGS (if any dynamic control needed)
${^WARNING_BITS} $?WARNINGS
$^X $*EXECUTABLE_NAME ...or some such
ARGV $*ARGFILE Note the P6 idiom for this handle:
for lines() {
# each time through loop
# proc a line from files named in ARGS
}
@ARGV @*ARGS
ARGVOUT TBD
$ARGV TBD
@F @_
%ENV %*ENV
@INC @*INC (but not for std library modules)
%INC %*INC (maybe, if needed)
%SIG event filters plus exception translation
$SIG{__WARN__} $*ON_WARN
$SIG{__DIE__} $*ON_DIE
${^OPEN} - This was internal; forget it
=head2 NOT YET DEFINED
The following items are not yet defined, but will need to be defined.
XXX Don't remove this line until this section is completely blank.
We also seem to have $*INC in the table at the top, @*INC in S19 and the table
immediately above, %*INC also in the table above.
The $?LANG and $*LANG variables are also confusing (both in S02).
=head3 Form.pm
These go in the Perl5 to Perl6 conversion table:
Perl6 Perl5
----- -----------------------------------------
- $% $FORMAT_PAGE_NUMBER
- HANDLE->format_page_number(EXPR)
- $= $FORMAT_LINES_PER_PAGE
- HANDLE->format_lines_per_page(EXPR)
- $- $FORMAT_LINES_LEFT
- HANDLE->format_lines_left(EXPR)
- $~ $FORMAT_NAME
- HANDLE->format_name(EXPR)
- $^ $FORMAT_TOP_NAME
- HANDLE->format_top_name(EXPR)
- $: $FORMAT_LINE_BREAK_CHARACTERS
- IO::Handle->format_line_break_characters
- $^L $FORMAT_FORMFEED
- IO::Handle->format_formfeed
- $^A $ACCUMULATOR
=head3 S15-unicode.pod
${^ENCODING} variable -- S32/Str.pod implies this is $?ENC
$?NF -- unicode normalisation form
${^UNICODE} variable
=head3 Infectious trait spec
${^TAINT} variable, which is pending, among other things, infectious trait spec
=head1 Additions
Please post errors and feedback to perl6-language. If you are making
a general laundry list, please separate messages by topic.
=for vim:set expandtab sw=4: