[DRAFT] Synopsis 28 - Special Names [DRAFT]
Larry Wall <larry@wall.org> Tim Nelson <wayland@wayland.id.au> Lyle Hopkins <webmaster@cosmicperl.com> Carl Mäsak <cmasak@gmail.com>
Created: 23 Feb 2009, created by Tim Nelson from miscellaneous documents lying around Last Modified: 17 Nov 2010 Version: 9
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.
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 $?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, $?LINE is different on every line of the program.
$?foo
$?LINE
The $*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 $*foo notation. Most of the standard globals listed below actually live either in the PROCESS or the GLOBAL package, where PROCESS contains globals belonging to the entire process, while 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 PROCESS package.
$*foo
PROCESS
GLOBAL
The $=foo variables are related to the $?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.
$=foo
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 $*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, $PROCESS::OUT is the stdout for the entire process, but each interpreter can set its own $GLOBAL::OUT to make $*OUT mean whatever it wants independently of other interpreters. Any dynamic scope may also declare a local meaning of $*OUT that applies only to called code. Likewise each thread could log its own errors to its own $*ERR, since a thread is a dynamic scope.
$*OUT
$PROCESS::OUT
$GLOBAL::OUT
$*ERR
The class Application collects a few common features of some of the special variables such as $*PERL, $?VM, $*KERNEL, etc.
Application
$*PERL
$?VM
$*KERNEL
class Application { has Str $.name; has Str $.auth; has Version $.version; }
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
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).
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
${^ENCODING} variable -- S32/Str.pod implies this is $?ENC $?NF -- unicode normalisation form ${^UNICODE} variable
${^TAINT} variable, which is pending, among other things, infectious trait spec
Please post errors and feedback to perl6-language. If you are making a general laundry list, please separate messages by topic.
1 POD Error
The following errors were encountered while parsing the POD:
Non-ASCII character seen before =encoding in 'Mäsak'. Assuming UTF-8
To install Perl6::Doc, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Perl6::Doc
CPAN shell
perl -MCPAN -e shell install Perl6::Doc
For more information on module installation, please visit the detailed CPAN module installation guide.